This Is Page Six Of Ten Pages                                      Basic Technical Articles
 
 
 
“Basic” Related Technical Articles of Possible Interest
 
 
INDEX OF ARTICLES:
 
 
Article One:  Below ... Citizen's Band Omni-Directional Ground Plane Antenna, A Primer (of sorts).
 
Article Two:  Below ... How to best acquire, un-install, remove, disassemble, inspect, pre-clean, repair and replace parts, prep, reassemble, final test and then re-install the Hy-Gain Penetrator 500 (or any other similar and/or comparable omni-directional ground plane antenna system.  (One man's opinion)
Article Three:  Below ... Decibel / This article is about the ratio of measures.
 
Article Four:  Please See Page Seven ... 1980s Midland "Precision Series" CB Radios & Strictly Export Models Included
 
Article Five:  Please See Page Seven
 
Article Six:  Please See Page Seven / Pending
 
 
 
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Article One: Citizen's Band Omni-Directional Ground Plane Antenna, a Primer (of sorts).
 
Antenna:  Any device which is purpose built that is capable of transmitting or receiving an electric signal.
 
 
This article was primarily written and intended to be an informational guide to assist you in selecting a high quality, low cost beginner or intermediate level citizens’ band radio base station antenna system.
 
It will also provide some basic knowledge of the history of radio communications in general and it will also discuss some basic history of the citizens’ band radio service in particular.
 
It will be limited to discussion of the ground plane antenna system only, which is just one of many different types of simplex antenna systems which are primarily built to legally operate in the FCC Part 15 authorized 11m  27 MHz bandwidth.
 
It will attempt to explain what ground plane antennas are, how they work, what they are built to do or not do and just what their main performance characteristics may or may not be.
 
In addition it is being written to provide the beginning (or returning) CB’er with relevant and hopefully useful information which is intended to assist you in correctly siteing, safely erecting and efficiently maintaining a base station antenna system which can be tailored to your personal requirements, preferences and performance expectations.
 
Whether you are new to citizens’ band radio or you are an old hand who has been out of the hobby for many years and who wants to re-connect is not important.  Basic radio equipment and related communications support item concerns are the same for everyone.  There is tons of equipment out there to consider, mentally evaluate and then select or pass on.
 
In the world of CB radio you can operate on anything from a fifty dollar used twenty-three channel mobile rig powered from a cheap plug in the wall 15 Watt DC/AC power supply to a thousand dollar + rig having hundreds of split upper and lower side band frequencies, light up jeweled control knobs, a couple of hundred different noise toys and an engine turned or painted and enameled rebel flag chassis case.  But none of that is going to do you a damn bit of good if your signal doesn’t get out.
 
And just like radio transceivers, your antenna system costs can run from a second hand, beat up thirty-five dollar Radio Shack clone to upwards of many hundreds of dollars, or more.
 
Arguably the antenna system is the most important and the most vitally necessary piece of equipment in a radio communications system.
 
Several different factors should be carefully considered before deciding on what type of antenna system to install.  And there are a host of related questions which you should ask yourself before you spend your first dollar.
 
First on your list of questions should be purpose.
 
What kind of time are you going to devote to this hobby?  Would a smaller and less expensive antenna system meet and serve part time use purposes and requirements?  Or are you going to be spending countless hours trying to talk to everybody you can no matter where they might be located?
 
What are you going to expect to be able to routinely do?  Are you going to be using your rig primarily for local contacts or are you going to expect to be able to communicate with distant operators far away?  And if so, how often are you going to want to be able to do this? 
 
What about your proposed antenna system’s physical footprint requirements?  More importantly what might any physical or zoning restrictions be?  Are you out in the country with unlimited air space or will you be operating out of a house or apartment in a suburban area in relatively close proximity to either neighbors or physical obstructions?
 
Will you be wanting to install a temporary antenna or a permanent antenna?  Will it be installed using a simple window mounting bracket or on a section of pipe or by using a chimney strap or roof tripod or some other type of quasi-permanent mounting assembly?
 
Are you going to consider installing a permanent tower structure?  If so where will it be located in proximity to your “shack”?  And how tall will you require it to be?  Will it free-stand or will it have to be supported or guyed?
 
How many different antennas might you eventually want to install on your tower and what would their total combined weight load, wind load or ice load be?
 
How about costs?
 
So, do you think you might want to spend a couple of hundred dollars or a couple of thousand dollars on this hobby, ball park figures?  Yes, It IS primarily a hobby in this day and time.  Once upon a time long, long ago many small business operators such as service station operators or garage owners, electricians, plumbers, auto parts houses, machine shops and countless others used and profited from installing CB radio communications systems in their shops and in their business vehicles.  But that was in an era long before the advent of car phones, lap top computers, cell phones and texting and the like.  Nowadays, you will not find a single small business out there using a cb radio system to augment their daily operations.
 
OK, purpose divided by costs should equal what?
 
A sensible pre-plan!
 
Sit down and decide first what kind of antenna system you want or need to start out with, either by necessity or design, and to what level of performance you eventually want to grow into, in order to be fully content with your operational limitations but most importantly, when and where are you going to have to get (in your mind) so that you can happily quit spending money!
 
This is what I mean about a pre-plan; at least as far as your choice of a base antenna system is concerned.
 
Decide what type of antenna system will ultimately work best for you and your individual requirements and be conscious of what any additional financial factors involved might be BEFORE you spend your money the FIRST TIME, much less more than once.
 
Now how do you go about doing that?  By knowing which antenna systems should best suit your personal needs according to their performance purposes and specifications.  And how do you do that?
 
Read!
 
If you are going to play around with radios you should have at least a basic knowledge of what radio really is, where it came from, who was responsible for learning and developing all the little things that make it so easy for you to simply turn a switch, push a button and converse with some total stranger that you would never know otherwise.
 
 
James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish [1] theoretical physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and even optics into a consistent theory. [2] Maxwell's equations demonstrated that electricity, magnetism and even light are all manifestations of the same phenomenon, namely the electromagnetic field. Subsequently, all other classic laws or equations of these disciplines were simplified cases of Maxwell's equations. Maxwell's achievements concerning electromagnetism have been called the "second great unification in physics", [3] after the first one realized by Isaac Newton.
 
Maxwell demonstrated that electric and magnetic fields travel through space in the form of waves, and at the constant speed of light. In 1864 Maxwell wrote A Dynamical Theory of the Electromagnetic Field. It was with this that he first proposed that light was in fact undulations in the same medium that is the cause of electric and magnetic phenomena. [4] His work in producing a unified model of electromagnetism is one of the greatest advances in physics.
 
In 1864 Maxwell published A Dynamical Theory of the Electromagnetic Field in which he showed that light was an electromagnetic phenomenon.
 
Definitions of Maxwell's theory of electromagnetism on the Web:
Electromagnetism is one of the four fundamental interactions of nature. It is the force that causes the interaction between electrically charged particles; the areas in which this happens are called electromagnetic fields.
 
 
************
 
 
Heinrich Rudolf Hertz (February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell. He was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect VHF or UHF radio waves.
 
The most dramatic prediction of Maxwell's theory of electromagnetism, published in 1865, was the existence of electromagnetic waves moving at the speed of light, and the conclusion that light itself was just such a wave. This challenged experimentalists to generate and detect electromagnetic radiation using some form of electrical apparatus.
 
The first clearly successful attempt was made by Heinrich Hertz in 1886. For his radio wave transmitter he used a high voltage induction coil, a condenser (capacitor, Leyden jar) and a spark gap - whose poles on either side are formed by spheres of 2 cm radius - to cause a spark discharge between the spark gap’s poles oscillating at a frequency determined by the values of the capacitor and the induction coil.
This first radio waves transmitter was basically, what we call today, an LC oscillator. More information about this subject could be found in basic electronics text books.
 
To prove there really was radiation emitted, it had to be detected. Hertz used a piece of copper wire, 1 mm thick, bent into a circle of a diameter of 7.5 cm, with a small brass sphere on one end, and the other end of the wire was pointed, with the point near the sphere. He added a screw mechanism so that the point could be moved very close to the sphere in a controlled fashion. This "receiver" was designed so that current oscillating back and forth in the wire would have a natural period close to that of the "transmitter" described above. The presence of oscillating charge in the receiver would be signaled by sparks across the (tiny) gap between the point and the sphere (typically, this gap was hundredths of a millimeter).  In this experiment Hertz confirmed Maxwell’s theories about the existence of electromagnetic radiation.
 
In more advanced experiments, Hertz measured the velocity of electromagnetic radiation and found it to be the same as the light’s velocity. He also showed that the nature of radio waves’ reflection and refraction was the same as those of light, and established beyond any doubt that light is a form of electromagnetic radiation obeying the Maxwell equations.
 
Summing up Hertz's importance: his experiments would soon trigger the invention of the wireless telegraph and radio by Marconi and others and TV.
 
In recognition of his work, the unit of frequency - one cycle per second - is named the “hertz”, in honor of Heinrich Hertz.
 
 
*** Antenna (radio) ***
    From Wikipedia, the free encyclopedia
 
An antenna (or aerial) is a transducer that transmits or receives electromagnetic waves. In other words, antennas convert electromagnetic radiation into electric current, or vice versa. Antennas generally deal in the transmission and reception of radio waves, and are a necessary part of all radio equipment. Antennas are used in systems such as radio and television broadcasting, point-to-point radio communication, wireless LAN, cell phones, radar, and spacecraft communication. Antennas are most commonly employed in air or outer space, but can also be operated under water or even through soil and rock at certain frequencies for short distances.
Physically, an antenna is an arrangement of one or more conductors, usually called elements in this context. In transmission, an alternating current is created in the elements by applying a voltage at the antenna terminals, causing the elements to radiate an electromagnetic field. In reception, the inverse occurs: an electromagnetic field from another source induces an alternating current in the elements and a corresponding voltage at the antenna's terminals. Some receiving antennas (such as parabolic and horn types) incorporate shaped reflective surfaces to collect the radio waves striking them and direct or focus them onto the actual conductive elements.
Some of the first rudimentary antennas were built in 1888 by Heinrich Hertz (1857–1894) in his pioneering experiments to prove the existence of electromagnetic waves predicted by the theory of James Clerk Maxwell. Hertz placed the emitter dipole in the focal point of a parabolic reflector. He published his work and installation drawings in Annalen der Physik und Chemie (vol. 36, 1889).
 
Terminology
 
The words antenna (plural: antennas [1] and aerial are used interchangeably; but usually a rigid metallic structure is termed an antenna and a wire format is called an aerial. In the United Kingdom and other British English speaking areas the term aerial is more common, even for rigid types. The noun aerial is occasionally written with a diaeresis mark—aërial—in recognition of the original spelling of the adjective aërial from which the noun is derived.
 
The origin of the word antenna relative to wireless apparatus is attributed to Guglielmo Marconi. In 1895, while testing early radio apparatuses in the Swiss Alps at Salvan, Switzerland in the Mont Blanc region, Marconi experimented with early wireless equipment. A 2.5 meter long pole, along which was carried a wire, was used as a radiating and receiving aerial element. In Italian a tent pole is known as l'antenna centrale, and the pole with a wire alongside it used as an aerial was simply called l'antenna. Until then wireless radiating transmitting and receiving elements were known simply as aerials or terminals. Marconi's use of the word antenna (Italian for pole) would become a popular term for what today is uniformly known as the antenna. [2]
 
A Hertzian or half-wave dipole antenna is a set of terminals that does not require the presence of a ground for its operation. A Marconi, Tesla, or quarter-wave monopole antenna is grounded. [3] A loaded antenna is an active antenna having an elongated portion of appreciable electrical length and having additional inductance or capacitance directly in series or shunt with the elongated portion so as to modify the standing wave pattern existing along the portion or to change the effective electrical length of the portion. An antenna grounding structure is a structure for establishing a reference potential level for operating the active antenna. It can be any structure closely associated with (or acting as) the ground which is connected to the terminal of the signal receiver or source opposing the active antenna terminal.
In colloquial usage, the word antenna may refer broadly to an entire assembly including support structure, enclosure (if any), etc. in addition to the purely functional components.
 
Overview
 
Antennas have practical uses for the transmission and reception of radio frequency signals such as radio and television. In air, those signals travel very quickly and with a very low transmission loss. The signals are absorbed when moving through more conductive materials, such as concrete walls or rock. When encountering an interface, the waves are partially reflected and partially transmitted through.
 
A common antenna is a vertical rod a quarter of a wavelength long. Such antennas are simple in construction, usually inexpensive, and both radiate in and receive from all horizontal directions (Omni-directional). One limitation of this antenna is that it does not radiate or receive in the direction in which the rod points. This region is called the antenna blind cone or null.
 
There are two fundamental types of antenna directional patterns, which with reference to a specific two dimensional plane (usually horizontal [parallel to the ground] or vertical (perpendicular to the ground), are either:
 
Omni-directional (radiates equally in all directions), such as a vertical rod (in the horizontal plane) or
Directional (radiates more in one direction than in the other).
 
In colloquial usage "Omni-directional" usually refers to all horizontal directions with reception above and below the antenna being reduced in favor of better reception (and thus range) near the horizon. A "directional" antenna usually refers to one focusing a narrow beam in a single specific direction such as a telescope or satellite dish, or, at least, focusing in a sector such as a 120° horizontal fan pattern in the case of a panel antenna at a cell site.
 
All antennas radiate some energy in all directions in free space but careful construction results in substantial transmission of energy in a preferred direction and negligible energy radiated in other directions. By adding additional elements (such as rods, loops or plates) and carefully arranging their length, spacing, and orientation, an antenna with desired directional properties can be created.
 
An antenna array is two or more simple antennas combined to produce a specific directional radiation pattern. In common usage an array is composed of active elements, such as a linear array of parallel dipoles fed as a "broadside array". A slightly different feed method could cause this same array of dipoles to radiate as an "end-fire array". Antenna arrays may be built up from any basic antenna type, such as dipoles, loops or slots.
 
Usually all of the elements are active (electrically fed) as in the log-periodic dipole array which offers modest gain and broad bandwidth and is traditionally used for television reception. Alternatively, a superficially similar dipole array, the Yagi-Uda Antenna (often abbreviated to "Yagi"), has only one active dipole element in a chain of parasitic dipole elements, and a very different performance with high gain over a narrow bandwidth.
 
An active element is electrically connected to the antenna terminals leading to the receiver or transmitter, as opposed to a parasitic element that modifies the antenna pattern without being connected directly. The active element(s) couple energy between the electromagnetic wave and the antenna terminals, thus any functioning antenna has at least one active element. A careful arrangement of parasitic elements, such as rods or coils, can improve the radiation pattern of the active element(s). Directors and reflectors are common parasitic elements.
 
An antenna lead-in is the medium, for example, a transmission line or feed line for conveying the signal energy between the signal source or receiver and the antenna. The antenna feed refers to the components between the antenna and an amplifier.
 
An antenna counterpoise is a structure of conductive material most closely associated with ground that may be insulated from or capacitively coupled to the natural ground. It aids in the function of the natural ground, particularly where variations (or limitations) of the characteristics of the natural ground interfere with its proper function. Such structures are usually connected to the terminal of a receiver or source opposite to the antenna terminal.
 
An antenna component is a portion of the antenna performing a distinct function and limited for use in an antenna, as for example, a reflector, director, or active antenna.
 
An electromagnetic wave refractor is a structure which is shaped or positioned to delay or accelerate transmitted electromagnetic waves, passing through such structure, an amount which varies over the wave front. The refractor alters the direction of propagation of the waves emitted from the structure with respect to the waves impinging on the structure. It can alternatively bring the wave to a focus or alter the wave front in other ways, such as to convert a spherical wave front to a planar wave front (or vice-versa). The velocities of the waves radiated have a component which is in the same direction (director) or in the opposite direction (reflector) as that of the velocity of the impinging wave.
 
A director is a parasitic element, usually a metallic conductive structure, which re-radiates into free space impinging electromagnetic radiation coming from or going to the active antenna, the velocity of the re-radiated wave having a component in the direction of the velocity of the impinging wave.
 
A reflector is a parasitic element, usually a metallic conductive structure (e.g., screen, rod or plate), which re-radiates back into free space impinging electromagnetic radiation coming from or going to the active antenna. The velocity of the returned wave has a component in a direction opposite to the direction of the velocity of the impinging wave. The reflector modifies the radiation of the active antenna.
 
An antenna coupling network is a passive network (which may be any combination of a resistive, inductive or capacitive circuit(s)) for transmitting the signal energy between the active antenna and a source (or receiver) of such signal energy.
Reciprocity
 
It is a fundamental property of antennas that the characteristics of an antenna described in the next section, such as gain, radiation pattern, impedance, bandwidth, resonant frequency and polarization, are the same whether the antenna is transmitting or receiving. For example, the "receiving pattern" (sensitivity as a function of direction) of an antenna when used for reception is identical to the radiation pattern of the antenna when it is driven and functions as a radiator. This is a consequence of the reciprocity theorem of electromagnetics. Therefore in discussions of antenna properties no distinction is usually made between receiving and transmitting terminology, and the antenna can be viewed as either transmitting or receiving, whichever is more convenient.
 
A necessary condition for the above reciprocity property is that the materials in the antenna and transmission medium are linear and reciprocal. Reciprocal (or bilateral) means that the material has the same response to an electric or magnetic field, or a current, in one direction, as it has to the field or current in the opposite direction. Most materials used in antennas meet these conditions, but some microwave antennas use high-tech components such as isolators and circulators, made of nonreciprocal materials such as ferrite or garnet. These can be used to give the antenna a different behavior on receiving than it has on transmitting, which can be useful in applications like radar.
 
Parameters:
 
Antenna measurement
 
There are several critical parameters affecting an antenna's performance that can be adjusted during the design process. These are resonant frequency, impedance, gain, aperture or radiation pattern, polarization, efficiency and bandwidth. Transmit antennas may also have a maximum power rating, and receive antennas differ in their noise rejection properties. All of these parameters can be measured through various means.
 
Resonant frequency
 
Many types of antenna are tuned to work at one particular frequency, and are effective only over a range of frequencies centered on this frequency, called the resonant frequency. These are called resonant antennas. The antenna acts as an electrical resonator. When driven at its resonant frequency, large standing waves of voltage and current are excited in the antenna elements. These large currents and voltages radiate intense electromagnetic waves, so the power radiated by the antenna is maximum at the resonant frequency.
 
In antennas made of thin linear conductive elements, the length of the driven element(s) determines the resonant frequency. To be resonant, the length of a driven element should typically be either half or a quarter of the wavelength at that frequency; these are called half-wave and quarter-wave antennas. The length referred to is not the physical length, but the electrical length of the element, which is the physical length divided by the velocity factor (the ratio of the speed of wave propagation in the wire to c0, the speed of light in a vacuum). Antennas are usually also resonant at multiples (harmonics) of the lowest resonant frequency.
 
Some antenna designs have multiple resonant frequencies, and some are relatively effective over a very broad range of frequencies. or bandwidth. One commonly known type of wide band antenna is the logarithmic or log-periodic antenna.
 
The resonant frequency also affects the impedance of the antenna. At resonance, the equivalent circuit of an antenna is a pure resistance, with no reactive component. At frequencies other than the resonant frequencies, the antenna has capacitance or inductance as well as resistance. An antenna can be made resonant at other frequencies besides its natural resonant frequency by compensating for these reactances by adding a loading coil or capacitor in series with it. Other properties of an antenna change with frequency, in particular the radiation pattern, so the antenna's operating frequency may be considerably different from the resonant frequency to optimize other important parameters.
 
Gain
 
Gain is a parameter which measures the degree of directivity of the antenna's radiation pattern. An antenna with a low gain emits radiation with about the same power in all directions, whereas a high-gain antenna will preferentially radiate in particular directions. Specifically, the antenna gain, directive gain, or power gain of an antenna is defined as the ratio of the intensity (power per unit surface) radiated by the antenna in the direction of its maximum output, at an arbitrary distance, divided by the intensity radiated at the same distance by a hypothetical isotropic antenna.
 
The gain of an antenna is a passive phenomenon.  Power is not added by the antenna, but simply redistributed to provide more radiated power in a certain direction than would be transmitted by an isotropic antenna. An antenna designer must take into account the application for the antenna when determining the gain. High-gain antennas have the advantage of longer range and better signal quality, but must be aimed carefully in a particular direction. Low-gain antennas have shorter range, but the orientation of the antenna is relatively inconsequential. For example, a dish antenna on a spacecraft is a high-gain device that must be pointed at the planet to be effective, whereas a typical Wi-Fi antenna in a laptop computer is low-gain, and as long as the base station is within range, the antenna can be in any orientation in space. It makes sense to improve horizontal range at the expense of reception above or below the antenna. Thus most antennas labeled "Omni-directional" really have some gain.[4]
 
In practice, the half-wave dipole is taken as a reference instead of the isotropic radiator. The gain is then given in dBd (decibels over dipole):
NOTE: 0 dBd = 2.15 dBi. It is vital in expressing gain values that the reference point be included. Failure to do so can lead to confusion and error.
 
Radiation pattern
 
The radiation pattern of an antenna is the geometric pattern of the relative field strengths of the field emitted by the antenna. For the ideal isotropic antenna, this would be a sphere. For a typical dipole, this would be a toroid. The radiation pattern of an antenna is typically represented by a three dimensional graph, or polar plots of the horizontal and vertical cross sections.
 
The radio waves emitted by different parts of an antenna typically interfere, causing maxima of radiation at some angles where the radio waves arrive in phase, and zero radiation at other angles where the radio waves arrive out of phase. So the radiation of most antennas shows a pattern of maxima or "lobes" at various angles. In a directional antenna designed to project radio waves in a particular direction, the lobe in that direction is larger than the others and is called the "main lobe". The other lobes represent unwanted radiation and are called "side lobes". The axis through the main lobe is called the "principle axis" or "bore sight axis".
 
Impedance
 
As an electro-magnetic wave travels through the different parts of the antenna system (radio, feed line, antenna, free space) it may encounter differences in impedance (E/H, V/I, etc.). At each interface, depending on the impedance match, some fraction of the wave's energy will reflect back to the source,[5] forming a standing wave in the feed line. The ratio of maximum power to minimum power in the wave can be measured and is called the standing wave ratio (SWR). A SWR of 1:1 is ideal. A SWR of 1.5:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although an SWR as high as 6:1 may still be usable with the right equipment. Minimizing impedance differences at each interface (impedance matching) will reduce SWR and maximize power transfer through each part of the antenna system.
 
Complex impedance of an antenna is related to the electrical length of the antenna at the wavelength in use. The impedance of an antenna can be matched to the feed line and radio by adjusting the impedance of the feed line, using the feed line as an impedance transformer. More commonly, the impedance is adjusted at the load (see below) with an antenna tuner, a balun, a matching transformer, matching networks composed of inductors and capacitors, or matching sections such as the gamma match.
 
Efficiency
 
Efficiency is the ratio of power actually radiated to the power put into the antenna terminals. A dummy load may have an SWR of 1:1 but an efficiency of 0, as it absorbs all power and radiates heat but very little RF energy, showing that SWR alone is not an effective measure of an antenna's efficiency. Radiation in an antenna is caused by radiation resistance which can only be measured as part of total resistance including loss resistance. Loss resistance usually results in heat generation rather than radiation, and reduces efficiency. Mathematically, efficiency is calculated as radiation resistance divided by total resistance.
 
Bandwidth
 
The bandwidth of an antenna is the range of frequencies over which it is effective, usually centered on the resonant frequency. The bandwidth of an antenna may be increased by several techniques, including using thicker wires, replacing wires with cages to simulate a thicker wire, tapering antenna components (like in a feed horn), and combining multiple antennas into a single assembly (array) and allowing the natural impedance of suitable inductive RF filter traps to select the correct antenna. All these attempts to increase bandwidth by adding capacitance to the surface area have a detrimental effect on efficiency by reducing the Q factor. They also have an adverse effect on the rejection of unwanted harmonics, on both received and transmitted signal frequencies. Small antennas are usually preferred for convenience, but there is a fundamental limit relating bandwidth, size and efficiency.
 
Polarization
 
The polarization of an antenna is the orientation of the electric field (E-plane) of the radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation. It has nothing in common with antenna directionality terms: "horizontal", "vertical" and "circular". Thus, a simple straight wire antenna will have one polarization when mounted vertically, and a different polarization when mounted horizontally. "Electromagnetic wave polarization filters" are structures which can be employed to act directly on the electromagnetic wave to filter out wave energy of an undesired polarization and to pass wave energy of a desired polarization.
The polarization of an antenna is the orientation of the electric field (E-plane) of the radio wave with respect to the Earth's surface and is determined by the physical structure of the antenna and by its orientation. It has nothing in common with antenna directionality terms: "horizontal", "vertical" and "circular". Thus, a simple straight wire antenna will have one polarization when mounted vertically, and a different polarization when mounted horizontally. "Electromagnetic wave polarization filters" are structures which can be employed to act directly on the electromagnetic wave to filter out wave energy of an undesired polarization and to pass wave energy of a desired polarization.
 
Reflections generally affect polarization. For radio waves the most important reflector is the ionosphere - signals which reflect from it will have their polarization changed unpredictably. For signals which are reflected by the ionosphere, polarization cannot be relied upon. For line-of-sight communications for which polarization can be relied upon, it can make a large difference in signal quality to have the transmitter and receiver using the same polarization; many tens of dB difference are commonly seen and this is more than enough to make the difference between reasonable communication and a broken link.
 
Polarization is largely predictable from antenna construction but, especially in directional antennas, the polarization of side lobes can be quite different from that of the main propagation lobe. For radio antennas, polarization corresponds to the orientation of the radiating element in an antenna. A vertical Omni-directional Wi-Fi antenna will have vertical polarization (the most common type). An exception is a class of elongated waveguide antennas in which vertically placed antennas are horizontally polarized. Many commercial antennas are marked as to the polarization of their emitted signals.
 
Polarization is the sum of the E-plane orientations over time projected onto an imaginary plane perpendicular to the direction of motion of the radio wave. In the most general case, polarization is elliptical, meaning that the polarization of the radio waves varies over time. Two special cases are linear polarization (the ellipse collapses into a line) and circular polarization (in which the two axes of the ellipse are equal). In linear polarization the antenna compels the electric field of the emitted radio wave to a particular orientation. Depending on the orientation of the antenna mounting, the usual linear cases are horizontal and vertical polarization. In circular polarization, the antenna continuously varies the electric field of the radio wave through all possible values of its orientation with regard to the Earth's surface. Circular polarizations, like elliptical ones, are classified as right-hand polarized or left-hand polarized using a "thumb in the direction of the propagation" rule. Optical researchers use the same rule of thumb, but pointing it in the direction of the emitter, not in the direction of propagation, and so are opposite to radio engineers' use.
 
In practice, regardless of confusing terminology, it is important that linearly polarized antennas be matched, lest the received signal strength be greatly reduced. So horizontal should be used with horizontal and vertical with vertical. Intermediate matchings will lose some signal strength, but not as much as a complete mismatch. Transmitters mounted on vehicles with large motional freedom commonly use circularly polarized antennas so that there will never be a complete mismatch with signals from other sources.
 
Transmission and reception
 
All of the antenna parameters are expressed in terms of a transmission antenna, but are identically applicable to a receiving antenna, due to reciprocity. Impedance, however, is not applied in an obvious way; for impedance, the impedance at the load (where the power is consumed) is most critical. For a transmitting antenna, this is the antenna itself. For a receiving antenna, this is at the (radio) receiver rather than at the antenna. Tuning is done by adjusting the length of an electrically long linear antenna to alter the electrical resonance of the antenna.
 
Antenna tuning is done by adjusting an inductance or capacitance combined with the active antenna (but distinct and separate from the active antenna). The inductance or capacitance provides the reactance which combines with the inherent reactance of the active antenna to establish a resonance in a circuit including the active antenna. The established resonance being at a frequency other than the natural electrical resonant frequency of the active antenna. Adjustment of the inductance or capacitance changes this resonance.
 
Antennas used for transmission have a maximum power rating, beyond which heating, arcing or sparking may occur in the components, which may cause them to be damaged or destroyed. Raising this maximum power rating usually requires larger and heavier components, which may require larger and heavier supporting structures. This is a concern only for transmitting antennas, as the power received by an antenna rarely exceeds the microwatt range.
 
Antennas designed specifically for reception might be optimized for noise rejection capabilities. An antenna shield is a conductive or low reluctance structure (such as a wire, plate or grid) which is adapted to be placed in the vicinity of an antenna to reduce, as by dissipation through a resistance or by conduction to ground, undesired electromagnetic radiation, or electric or magnetic fields, which are directed toward the active antenna from an external source or which emanate from the active antenna. Other methods to optimize for noise rejection can be done by selecting a narrow bandwidth so that noise from other frequencies is rejected, or selecting a specific radiation pattern to reject noise from a specific direction, or by selecting a polarization different from the noise polarization, or by selecting an antenna that favors either the electric or magnetic field.
 
For instance, an antenna to be used for reception of low frequencies (below about ten megahertz) will be subject to both man-made noise from motors and other machinery, and from natural sources such as lightning. Successfully rejecting these forms of noise is an important antenna feature. A small coil of wire with many turns is more able to reject such noise than a vertical antenna. However, the vertical will radiate much more effectively on transmit, where extraneous signals are not a concern.
 
Basic antenna models
 
Typical US multiband TV antenna (aerial)
 
There are many variations of antennas. Below are a few basic models. More can be found in Category:  Radio frequency antenna types.
 
The isotropic radiator is a purely theoretical antenna that radiates equally in all directions. It is considered to be a point in space with no dimensions and no mass. This antenna cannot physically exist, but is useful as a theoretical model for comparison with all other antennas. Most antennas' gains are measured with reference to an isotropic radiator, and are rated in dBi (decibels with respect to an isotropic radiator).
 
The dipole antenna is simply two wires pointed in opposite directions arranged either horizontally or vertically, with one end of each wire connected to the radio and the other end hanging free in space. Since this is the simplest practical antenna, it is also used as a reference model for other antennas; gain with respect to a dipole is labeled as dBd. Generally, the dipole is considered to be Omni-directional in the plane perpendicular to the axis of the antenna, but it has deep nulls in the directions of the axis. Variations of the dipole include the folded dipole, the half wave antenna, the ground plane antenna, the whip, and the J-pole.
 
The Yagi-Uda antenna is a directional variation of the dipole with parasitic elements added which are functionality similar to adding a reflector and lenses (directors) to focus a filament light bulb.
 
The random wire antenna is simply a very long (at least one quarter wavelength) wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available. Folding will reduce effectiveness and make theoretical analysis extremely difficult. (The added length helps more than the folding typically hurts.) Typically, a random wire antenna will also require an antenna tuner, as it might have a random impedance that varies non-linearly with frequency.
 
The random wire antenna is simply a very long (at least one quarter wavelength) wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available. Folding will reduce effectiveness and make theoretical analysis extremely difficult. (The added length helps more than the folding typically hurts.) Typically, a random wire antenna will also require an antenna tuner, as it might have a random impedance that varies non-linearly with frequency.
 
The horn is used where high gain is needed, the wavelength is short (microwave) and space is not an issue. Horns can be narrow band or wide band, depending on their shape. A horn can be built for any frequency, but horns for lower frequencies are typically impractical. Horns are also frequently used as reference antennas.
 
The horn is used where high gain is needed, the wavelength is short (microwave) and space is not an issue. Horns can be narrow band or wide band, depending on their shape. A horn can be built for any frequency, but horns for lower frequencies are typically impractical. Horns are also frequently used as reference antennas.
 
The parabolic antenna consists of an active element at the focus of a parabolic reflector to reflect the waves into a plane wave. Like the horn it is used for high gain, microwave applications, such as satellite dishes.
 
The patch antenna consists mainly of a square conductor mounted over a ground plane. Another example of a planar antenna is the tapered slot antenna (TSA), as the Vivaldi-antenna.
 
Practical antennas
 
Although any circuit can radiate if driven with a signal of high enough frequency, most practical antennas are specially designed to radiate efficiently at a particular frequency. An example of an inefficient antenna is the simple Hertzian dipole antenna, which radiates over wide range of frequencies and is useful for its small size. A more efficient variation of this is the half-wave dipole, which radiates with high efficiency when the signal wavelength is twice the electrical length of the antenna.
 
One of the goals of antenna design is to minimize the reactance of the device so that it appears as a resistive load. An "antenna inherent reactance" includes not only the distributed reactance of the active antenna but also the natural reactance due to its location and surroundings (as for example, the capacity relation inherent in the position of the active antenna relative to ground). Reactance diverts energy into the reactive field, which causes unwanted currents that heat the antenna and associated wiring, thereby wasting energy without contributing to the radiated output. Reactance can be eliminated by operating the antenna at its resonant frequency, when its capacitive and inductive reactances are equal and opposite, resulting in a net zero reactive current. If this is not possible, compensating inductors or capacitors can instead be added to the antenna to cancel its reactance as far as the source is concerned.
 
Once the reactance has been eliminated, what remains is a pure resistance, which is the sum of two parts: the ohmic resistance of the conductors, and the radiation resistance. Power absorbed by the ohmic resistance becomes waste heat, and that absorbed by the radiation resistance becomes radiated electromagnetic energy. The greater the ratio of radiation resistance to ohmic resistance, the more efficient the antenna.
 
Effect of ground
 
Antennas are typically used in an environment where other objects are present that may have an effect on their performance. Height above ground has a very significant effect on the radiation pattern of some antenna types.
 
At frequencies used in antennas, the ground behaves mainly as a dielectric. The conductivity of ground at these frequencies is negligible. When an electromagnetic wave arrives at the surface of an object, two waves are created: one enters the dielectric and the other is reflected. If the object is a conductor, the transmitted wave is negligible and the reflected wave has almost the same amplitude as the incident one. When the object is a dielectric, the fraction reflected depends (among others things) on the angle of incidence. When the angle of incidence is small (that is, the wave arrives almost perpendicularly) most of the energy traverses the surface and very little is reflected. When the angle of incidence is near 90° (grazing incidence) almost all the wave is reflected.
 
Most of the electromagnetic waves emitted by an antenna to the ground below the antenna at moderate (say < 60°) angles of incidence enter the earth and are absorbed (lost). But waves emitted to the ground at grazing angles, far from the antenna, are almost totally reflected. At grazing angles, the ground behaves as a mirror. Quality of reflection depends on the nature of the surface. When the irregularities of the surface are smaller than the wavelength reflection is good.
 
The wave reflected by earth can be considered as emitted by the image antenna
 
This means that the receptor "sees" the real antenna and, under the ground, the image of the antenna reflected by the ground. If the ground has irregularities, the image will appear fuzzy.
 
If the receiver is placed at some height above the ground, waves reflected by ground will travel a little longer distance to arrive to the receiver than direct waves. The distance will be the same only if the receiver is close to ground.
 
The situation is a bit more complex because the reflection of electromagnetic waves depends on the polarization of the incident wave. As the refractive index of the ground (average value) is bigger than the refractive index of the air, the direction of the component of the electric field parallel to the ground inverses at the reflection. This is equivalent to a phase shift of radians or 180°. The vertical component of the electric field reflects without changing direction. This sign inversion of the parallel component and the non-inversion of the perpendicular component would also happen if the ground were a good electrical conductor.
 
The vertical component of the current reflects without changing sign. The horizontal component reverses sign at reflection.
 
This means that a receiving antenna "sees" the image antenna with the current in the same direction if the antenna is vertical or with the current inverted if the antenna is horizontal.
 
For a vertical polarized emission antenna the far electric field of the electromagnetic wave produced by the direct ray plus the reflected ray is:
 
The sign inversion for the parallel field case just changes a cosine to a sine:
 
In these two equations:
is the electrical field radiated by the antenna if there were no ground.
is the wave number.
is the wave length.
is the distance between antenna and its image (twice the height of the center of the antenna).
 
 
For emitting and receiving antenna situated near the ground (in a building or on a mast) far from each other, distances traveled by direct and reflected rays are nearly the same. There is no induced phase shift. If the emission is polarized vertically the two fields (direct and reflected) add and there is a maximum of received signal. If the emission is polarized horizontally the two signals subtracts and the received signal is minimum. This is depicted in the image at right. In the case of vertical polarization, there is always a maximum at earth level (left pattern). For horizontal polarization, there is always a minimum at earth level. Note that in these drawings the ground is considered as a perfect mirror, even for low angles of incidence. In these drawings the distance between the antenna and its image is just a few wavelengths. For greater distances, the number of lobes increases.
 
Note that the situation is different–and more complex–if reflections in the ionosphere occur. This happens over very long distances (thousands of kilometers). There is not a direct ray but several reflected rays that add with different phase shifts.
Note that the situation is different–and more complex–if reflections in the ionosphere occur. This happens over very long distances (thousands of kilometers). There is not a direct ray but several reflected rays that add with different phase shifts.
 
This is the reason why almost all public address radio emissions have vertical polarization. As public users are near ground, horizontal polarized emissions would be poorly received. Observe household and automobile radio receivers. They all have vertical antennas or horizontal ferrite antennas for vertical polarized emissions. In cases where the receiving antenna must work in any position, as in mobile phones, the emitter and receivers in base stations use circular polarized electromagnetic waves.
 
Classical (analog) television emissions are an exception. They are almost always horizontally polarized, because the presence of buildings makes it unlikely that a good emitter antenna image will appear. However, these same buildings reflect the electromagnetic waves and can create ghost images. Using horizontal polarization, reflections are attenuated because of the low reflection of electromagnetic waves whose magnetic field is parallel to the dielectric surface near the Brewster's angle. Vertically polarized analog television has been used in some rural areas. In digital terrestrial television reflections are less obtrusive, due to the inherent robustness of digital signaling and built-in error correction.
 
Mutual impedance and interaction between antennas
 
Mutual impedance between parallel dipoles not staggered. Curves Re and Im are the resistive and reactive parts of the impedance.
Current circulating in any antenna induces currents in all others. One can postulate a mutual impedance between two antennas that has the same significance as the in ordinary coupled inductors. The mutual impedance  between two antennas is defined as:
 
where  is the current flowing in antenna 1 and  is the voltage that would have to be applied to antenna 2–with antenna 1 removed–to produce the current in the antenna 2 that was produced by antenna 1.
From this definition, the currents and voltages applied in a set of coupled antennas are:
 
where:
is the voltage applied to the antenna i
is the impedance of antenna i
is the mutual impedance between antennas i and j
Note that, as is the case for mutual inductances,
 
This is a consequence of Lorentz reciprocity. If some of the elements are not fed (there is a short circuit instead a feeder cable), as is the case in television antennas (Yagi-Uda antennas), the corresponding  are zero. Those elements are called parasitic elements. Parasitic elements are unpowered elements that either reflect or absorb and reradiate RF energy.
 
In some geometrical settings, the mutual impedance between antennas can be zero. This is the case for crossed dipoles used in circular polarization antennas.
                                                                                                                                 ... With appreciated input by Don Rudolph W9BHI
 
*** Citizens band radio ***
    From Wikipedia, the free encyclopedia
 
 
 
Citizens' Band radio (often shortened to CB radio) is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz (11 m) band.
 
Origins
 
The Citizens' Band radio service originated in the United States as one of several personal radio services regulated by the Federal Communications Commission (FCC). These services began in 1945 to permit citizens a radio band for personal communication (e.g., radio-controlled models, family communications, and individual businesses). In 1948, the original "Class D" CB Radios were to be operated on the 460 MHz–470 MHz UHF band. [2] There were two classes of CB: A and B. Class B radios had simpler technical requirements but were limited to a smaller range of frequencies. Al Gross, inventor of the walkie-talkie, started Citizen's Radio Corp. in the late 1940s to merchandise Class B handhelds for the general public. [3]
 
Ultra-high frequency, or UHF, radios, at the time, were neither practical nor affordable for the average consumer. In 1958 [4] the Class D CB service was moved to 27 MHz, and this band became what is popularly known as CB. There were only 23 channels at the time; the first 22 were taken from what used to be an Amateur 11-meter band, while channel 23 was shared with radio-controlled devices. Some hobbyists continue to use the designation "11 meters" to refer to the Citizens' Band and adjoining frequencies. Part 95 of the Code of Federal Regulations regulated the Class D CB service, on the 27 MHz band, as of the 1970s. [citation needed
 
Most of the 460 MHz–470 MHz band was reassigned for business and public safety uses, but Class A CB is the ancestor of the present General Mobile Radio Service GMRS. Class B, in the same vein, is a more distant ancestor of the Family Radio Service. The Multi-Use Radio Service is another two-way radio service, in the VHF high band. An unsuccessful petition was made in 1973 to create a Class E CB service at 220 MHz, this was opposed by amateur radio organizations [5] and others. There are several other classes of personal radio services for specialized purposes such as remote control devices.
 
In the 1960s, the service was popular with small trade businesses (e.g., electricians, plumbers, carpenters), as well as truck drivers and radio hobbyists. By the late 60s the advancement of solid-state electronics allowed the weight, size, and cost of the radios to decrease, giving the general public access to a communications medium that had previously been only available to specialists. Many CB clubs were formed, and a special CB slang language evolved, used alongside 10-codes similar to those used in the emergency services.
 
Growing popularity in the 1970
 
Following the 1973 oil crisis, the U.S. government imposed a nationwide 55 mph speed limit, and fuel shortages and rationing were widespread. CB radio was often used, especially by truckers, to locate service stations with a supply of gasoline, to notify other drivers of speed traps, and to organize blockades and convoys in a 1974 strike protesting the new speed limit and other trucking regulations. Throughout the 1970s and early 1980s, a phenomenon was developing over the CB radio. Similar to the Internet chat rooms a quarter century later, the CB allowed people to get to know one another in a quasi-anonymous manner. Many movies and stories about CBers and the culture on-the-air developed.
 
The prominent use of [6] CB radios in 1970s-era films (see list below) such as Smokey and the Bandit (1977), Convoy (1978), and television shows like Movin' On (debuted 1974) and The Dukes of Hazzard (debuted 1979) bolstered the appeal of CB radio. Moreover, popular novelty songs such as C.W. McCall's Convoy (1976) helped establish CB radio as a nationwide craze in the USA in the mid- to late-1970s.
 
Originally, CB required a license and fee (it was $20.00 in the early 70's; and $4.00 in the late 70's), and the use of a call sign, but when the CB craze was at its peak, many people ignored this requirement and used made-up nicknames or "handles". The many restrictions on the authorized use of CB radio led to widespread disregard of the regulations, most notably in antenna height, distance restriction for communications, licensing and the use of call signs, and allowable transmitter power. After the FCC started receiving over 1,000,000 license applications a month, the license requirement was dropped entirely.
 
Originally, there were only 23 CB channels in the U.S.; the present 40-channel band plan did not come along until 1977. Channel 9 was reserved for emergency use in 1969. [7] Channel 10 was used for highway communications at first, then, it was Channel 10 east of the Mississippi River, and channel 19 west of the Mississippi; then later Channel 19 became the preferred highway channel in most areas, as it did not have adjacent-channel interference problems with channel 9. Many CB'ers called Channel 19 "the trucker's channel".
 
Until 1975, [8] only channels 9–15 and 23 [9] could be used for "inter station" calls to other licensees. Channels 1–8 and 16–22 were reserved for "intra station" communications among units under the same license.[10] After the inter station/intra station rule was dropped, Channel 11 was reserved as a calling frequency for the sole purpose of establishing communications; however this was withdrawn in 1977. [11] During this time period, it was common for many CB radios to have these "inter station" channels 'colored' on their dial, whilst the other channels were 'clear' or 'normal'; with the exception of Channel 9 - it was usually colored Red. Also, it was common for Single Sideband (SSB) users to use Channel 16 as 'their' channel.
 
It was also very common for towns relatively close together, to 'adopt' one of these "inter station" channels as their 'home' channel. This accomplished two things: first, this help prevent overcrowding on Ch 11, and 2nd; this allowed a CB'er to go to that town's 'home channel' to try and contact another CB'er from that town, instead of a general 'call' on Ch 11.
In more recent years, CB has lost much of its original appeal due to development of mobile phones, the Internet, and Family Radio Service. The changing radio wave propagation for long-distance communications, due to the 11 year sunspot cycle, is always a factor for these frequencies. In addition, CB in some respects became a victim of its own intense popularity. Because of the millions of users jammed onto frequencies during the mid-to-late 1970s and early 1980s, channels often were intolerably noisy and communication became difficult. Many CBers started to use their radios less frequently or not at all after this period.
In more recent years, CB has lost much of its original appeal due to development of mobile phones, the Internet, and Family Radio Service. The changing radio wave propagation for long-distance communications, due to the 11 year sunspot cycle, is always a factor for these frequencies. In addition, CB in some respects became a victim of its own intense popularity. Because of the millions of users jammed onto frequencies during the mid-to-late 1970s and early 1980s, channels often were intolerably noisy and communication became difficult. Many CBers started to use their radios less frequently or not at all after this period.
 
Right about now I suppose that you’re beginning to wonder … Just what in the heck has all that got to do with what kind of CB antenna system I need (or don’t need) to install and just how much money do I need (or don’t need) to spend on it?
 
Here are some of the answers to some of those questions …
 
Everybody and his damn brother who manufactures or builds CB antennas, and whomever has ever manufactured or built CB antennas and/or whomever ever will manufacture or build CB antennas in the future uses, has used or will use many of the type-phrases, descriptions and measurements listed in the write-up above to define, specify, advertise and/or rate their products! 
 
And a lot of the time they do so incorrectly and on purpose.
 
Definitions or claims of purported antenna specifications ratings such as: Bandwidth, Efficiency, Gain, Impedance, Polarization, Power Rating, Radiation Pattern, Reception, Resonant Frequency, Standing Wave, Transmission, Velocity, etc. are often exaggerated, misleading or willfully misstated.
 
If you KNOW what these terms actually mean and how they are supposed to be correctly applied or compared you will have a much more accurate understanding of the capabilities of the antenna system you choose.
 
GROUND PLANE ANTENNA SYSTEMS
 
Any of the end-fed Omni-directional ground plane antenna assemblies will make an excellent choice for a beginner or intermediate usage CB communications antenna assembly.  They are all relatively inexpensive. They are all fairly quick and easy to assemble (or disassemble and store if you have to) and none of them require a large amount of “sky” to put up.  And they all tend to perform very well given their approximate sizes despite some limited performance specification issues.
 
Basic design types of CB base and/or mobile antennas interchangeably include, among others, the quarter wavelength, the half wavelength, the 5/8ths wavelength and the .64 wavelength.  There are other designs which run all the way up to a full wavelength but these are not addressed here mainly because they are not practical as a beginner or intermediate type CB antenna system and that is not where I wish to take this discussion at this point in time.
 
A quarter wavelength, end fed vertical radiator base station type antenna is among the least expensive base antenna systems out there.  It is an Omni-directional type antenna and it is very suitable for use as a beginner’s antenna.  It usually stands somewhere around six to eight feet tall.  Several models are of strictly mechanical construction but some models have an enclosed base coil load.  It performs well for several miles in more or less flat or gently rolling terrain.  And it will perform even better if you can stick some height under it such as a 21’ section of pipe, a permanent roof mount with a raised center mast pole or a couple of tower sections equipped with same.
 
A half wavelength, end fed vertical radiator base station type antenna is normally a little more expensive than a quarter wavelength antenna.  It is an Omni-directional type, (usually) coil loaded type antenna and it is usually physically larger in both height and circumference than a quarter wavelength base antenna as it is most often equipped with a varying number of horizontal elements which markedly increase its radiation pattern and improve both the system’s transmit and reception quality and range.  And it will usually cover a larger service area than a similarly constructed quarter wavelength base antenna.  It too performs better if you can raise it above ground elevation either by natural or artificial means.
 
A 5/8ths wavelength, end fed vertical radiator base station type antenna is probably the most common full size and the most powerfully rated cb antenna in general use today.  It is generally taller (usually somewhere around 23’) and almost always utilizes some sort of horizontal element system which can and usually does range up to 210” in circumference (full quarter wavelength). It is a great improvement over any similarly constructed half wavelength type base antenna.  It is Omni-directional and it may be constructed as either mechanical (utilizing some sort of a matching rod or sliding trombone type frequency and ohmage setting adjustment) or it may be internally base coil loaded.  It will cover the largest physical area of any of the antenna systems described so far in varying terrains.  It will transmit and receive further, clearer and more dependably than either the quarter wavelength or the half wavelength base antennas.  It is generally the most expensive of the three types.  It can deliver up to a solid 5 Db power gain.  As with the other types mentioned it too performs better the higher it is above ground elevation.
 
A .64 wavelength, end fed vertical radiator type base station type antenna is very similar to the 5/8th wavelength system.  It is usually somewhere around 23’ in vertical height and it does usually utilize the 210” circumference full quarter wavelength horizontal radials.  They have never been prolific in either quantity or performance and their output performance characteristics are only marginally better (if any) than the 5/8th wavelength systems.  Back in the ‘70s when they were more or less in vogue they were marketed almost exclusively by Taylor Radio or Radio Shack and they were indeed the top dollar antenna systems costing more on average than any other type of end fed, vertical radiator Omni-directional antenna system.
 
The average dB gain for just about any ground plane antenna system usually runs somewhere around 3 to 5 dB.  The average total weight usually comes in somewhere around ten pounds or less.  And the average height can run all the way up to 22+ feet with an the average horizontal radial circumference of up to 16 feet or less.
 
Most all of the above described antenna systems are of all aluminum construction.  In recent years a plethora of plastic and/or fiberglass base station antennas have been introduced to the CB radio marketplace.  They almost always cost less, are almost always overrated in power output, overrated in performance specifications (as opposed to the all aluminum systems), underrated in SWR measurements and almost always Tx off frequency especially if additional input power is introduced into the transmission line. 
 
But then in all honesty, just about everything else does too!
 
Now let’s talk about Proper Siteing.
 
Any radio system works better if you adhere to certain cardinal rules and/or guidelines.  One of these guidelines is to always try to use a good quality, low loss type of coaxial cable in your power feed line and to keep all of your coaxial cables as short as possible.  One way to achieve this is to site your elevation pole or tower as close to your “shack” as possible.  The longer the power feed line run the larger the subsequent feed line power loss, therefore you will generally have to purchase the larger, better shielded and more expensive coaxial cables, such as RG-213 or better to keep your performance levels up to their potential.  If you have to make a decision as to where things need to be physically located it is far more preferable to try and site your “shack” location to your antenna pole or tower than it is to do the opposite.
 
Your number one priority when installing ANY kind of antenna is always safety.  You must make a conscious decision to attempt to safely site and install the antenna structure where it won’t get you killed when you initially put it up or when you climb up the thing every time you feel like you need to inspect or replace anything.
 
Stay away from all installed wiring whether it is utility type, improperly coded structural or outbuilding wiring or whatever kind of wiring.  Treat all wiring as if it’s going to be the very last wire you will ever touch.  Because it just might be.  Then, and only then do you try to site and install the antenna structure where it will do you the most good as far as natural or artificial elevation (such as the high yard side of the house), or where any permanent or natural obstructions might be concerned such as buildings, utility line easements or tall trees which leaf out every spring.
 
Pole or Tower Mounting?
 
If you are only going to be doing a small or medium amount of DXing you might strongly consider using a 21’ section of steel pipe for your antenna structure.  It’s quick; it’s easily installed and only requires one elevated structural tie in at the roof or gable’s highest elevation point.  And its dirt cheap as compared to the expenses of buying and installing a new or used self- supporting or attached and/or guyed communications tower of any kind.
 
Here in central Kentucky used communications towers are relatively cheap.  Since the advent of cable and satellite television nobody wants an old unused, rusted tower left attached to their house.  That is unless they keep the bottom two sections installed just so they can get up on their roof if and when they need to.  In most cases, old used Rohn and/or ladder type tower sections can be had for free simply for taking them down.
 
And then again there’s the question of whether you own the property where you live or not.  If you don’t own chances are the property owner won’t allow you to put up a tower regardless, simply because of the insurance liability which you just might create for him (and yourself) if and when you should take a direct lightning strike.  And you certainly aren’t going to want to be constantly taking down and relocating an average forty or fifty foot tall tower ever time you choose (or have) to move or relocate.
 
There are many more types and models of cb antenna systems out there that one could acquire and use.  There are directional beam systems which can be operated in either the vertical or horizontal modes or both.  There are wire antenna systems which can range in size from a few yards across to as wide as your property may be deep.  And there are specialty radio and antenna systems out there that you would have to go back home and beg your momma’ for a loan to buy when daddy couldn’t hear you.
 
In summary …
 
The points that I am trying to convey are simply these.  Make a plan. Establish a budget.  Acquire your equipment in an orderly fashion based on your needs and not based on uninformed, poor or foolish selections.
 
This will allow you to enjoy everything you acquire or purchase and to expand and grow your hobby at your desired pace without having to buy unnecessary or redundant types of equipment over and over again just because you didn’t logically think things through in the first place.
 
In the world of CB radio antenna systems just like in the world of CB radio equipment …
 
Just because something’s a little bigger, or a little newer or more heavily optioned or more expensive, that doesn’t mean that it’s going to work one damn bit better for YOU.
 
Everyone’s situation is different.
 
 
Thank you for reading my article.                  
 
Jim Dent                                                                                                                     ... With appreciated input from Don Rudolph W9BHI
January 31, 2011
 
 
************************************************************************************************************************
 
 
Article Two:  How to best acquire, un-install, remove, disassemble, inspect, pre-clean, repair and replace parts, prep, reassemble, final test and then re-install the Hy-Gain Penetrator 500 (or any other similar and/or comparable Omni-Directional ground plane antenna system.  (One man's opinion)
 
 
READ THIS AUTHOR’S DISCLAIMER COMPLETELY!
 
While the application of any knowledge in any endeavour is far preferable to operating in partial or complete ignorance, at least to me, the following information is being presented solely with the intentions to enlighten and to entertain you, the reader, with some insights into the way I go about performing the following stated and described actions as an integral and necessary part of my hobby.
 
These methods of operation are certainly not Gospel.   Nor are they foolproof.  They are simply my methods.  And some of these actions can be extremely dangerous and may result in great misfortune if the utmost care is not taken.
 
 
I CAN NOT AND WILL NOT BE RESPONSIBLE FOR ANY ACTIONS TAKEN BY YOU THE READER OR BY ANY OTHER PERSON OPERATING AT YOUR ASSISTANCE OR DIRECTION WHO MIGHT TEND TO BE CAUSED GREAT BODILY HARM OR SERIOUS PERSONAL INJURY OR EVEN DEATH AS A RESULT OF HAVING ATTEMPTED TO EMPLOY THESE METHODS FOR YOUR OR THEIR OWN INTERESTS.
 
 
 
The Hy-Gain Penetrator Order 500, end-fed, omni-directional, 5/8ths wavelength ground plane antenna system is arguably the finest citizens’ band base station antenna system that has ever been built and mass produced.
 
It was manufactured in two different basic configurations under two different order numbers and it was marketed directly by Hy-Gain Electronics from the mid ‘60s thru the mid to late ‘80s.  However, all things considered there were three different Penetrators marketed.
 
It consisted of anywhere from seventeen aluminum tubing sections to thirteen aluminum tubing sections, depending on which version you have to work with.
 
All three configurations had a five section end fed vertical radiator which measured out at 23’ 9.5” and 23’ 6.5” respectively depending on the individual models.
 
All three configurations had a five section end fed vertical radiator which measured out at 23’ 9.5” and 23’ 6.5” respectively depending on the individual models.
 
The original design Penetrator 500 configuration had four, three section horizontal gain elements. 
 
The later Penetrator 500 configuration and the Super Golden Penetrator Order 525 differed from the original in that they both had four, two section horizontal gain elements. 
 
The horizontal elements on all three models measured out at 105” (full ¼ wave length) regardless.
 
This is a working text that will explain how I refurbish my P500s from takedown to boxing for resale.  It isn’t all that quick and it isn’t all that easy.  But it’s not rocket science either and anyone can accomplish the feat if they set their mind to it and invest the necessary amounts of both time and patience, and maybe a little cash for necessary replacement parts.
 
You will find that several of the steps I list involve using specialized equipment or tooling that will not be owned by or readily available to the average individual.  However, all of these items can be obtained by the rebuilder at a fair cost if he knows where to go looking for them.
 
The steps I will cover and discuss will be (1) Locating and acquiring the antenna system you want.  (2) The un-installation and safe removal of the old installed antenna assembly , the partial disassembly and lowering of same and disassembling and removing the sectioned pole or communications tower structure (3)  The inspection and pre-cleaning of the old used antenna sections and all other related plastic parts (4)  The replacement or repair of any missing or defective and unusable aluminum sections or related plastic parts (5) The re-preparation of all aluminum sections to insure electrical continuity (6) The reassembly and testing of your completed work and (7)  The safe and effective reinstallation of your newly refurbished antenna system.
 
Step 1.  Your project will obviously start with either the locating and/or acquisition of the antenna system you want.
 
You may be fortunate enough to locate and buy one from a friend or acquaintance or thru eBay which has already been taken down and disassembled. 
Or, you may have to locate and acquire an old, used system which is still up in the air somewhere and which may have been hanging up there for the last twenty or thirty years or even longer. 
 
If you do indeed acquire a system that is already down and in your hands you will most likely be ready to proceed to step 3 or even step 4. 
 
However, we will assume for the sake of this article that you have not been able to do so and I will continue the dialogue. 
 
The customary way to find one of these things is by driving around and paying attention to everybody else’s business.  And obviously, you need to know just exactly what you are looking for looks like in the first place.
 
Penetrators are pretty much straight forward in appearance but everything up there tends to look a little different when you are forty or fifty feet or so away and fifty to sixty feet lower than it is.
 
A good pair of binoculars will help you pick out distinguishing characteristics, such as the front matching rod or the vertical and horizontal aluminum tubing counts or the top static arrestor assembly “the top hat” very easily, if it is still there.
 
Then there’s always the fall back method which actually works quite well and quite often.  Park, go up to the front door, ring the bell and ask questions.
You will be surprised how many folks who answer the door will know exactly what’s up there (if they did indeed put it up there in the first place). 
You will also be surprised at how many of the properties are owned by widows’ of the original installer. 
 
Then again, a lot of folks buy and move into or let for rent residential properties where the towers and antenna assemblies are already in place and have little or no use for them whatsoever.
 
A lot of old antennas can be found still installed on buildings that are either vacant, unoccupied or for sale.  If there is a FOR SALE sign displayed this narrows your time and options down greatly.  If there is not you can ask around the area and see if anyone can provide you with information about the property.  Or you can go to that county’s records division and undertake a recorded property title search yourself at no charge.
 
The original owner or installer is usually a person who participated in citizen’ band radio years ago or way back when it was far more popular than it is today.  Quite often they have given up the hobby completely and have no qualms whatsoever with selling or parting with their equipment.  They have a good idea what their equipment was worth to them back then and won’t mind telling you in clear language what it is worth to them today.
 
The widows of former CB’ers should be treated with the utmost respect.  They have most likely lost a loved one with whom they have probably shared a major portion of their life.  Usually they have absolutely no idea what the equipment even does, much less what it might be worth (or not) or how to even go about disposing of it. 
 
You will indeed be a low life bastard if you take unfair advantage of a situation such as this.  It is not the same as a yard sale.  I find that it helps to put the image of your own father or mother or your “widowed” wife into your head then into the conversation and the equation, and a sense of fair play just seems to come more naturally.
 
The folks who buy a property to live in it or the folks who buy a property specifically to rent it out are usually the most likely to have just the antenna assemblies left there (no inside equipment) and they are almost always still mounted on a rusty old sections pole or tower that may or not be safe to climb. 
They usually don’t want to have to pay the expense of having the old pole sections or the tower sections taken down and hauled away.
 
But they usually don’t want the added property insurance liability of having an old pole assembly or a rusted up fifty foot “Lightning Rod” with unused and unwanted antennas on their property either. 
 
I have found that most often the property owners are usually happy to give you the antenna simply for taking it down and removing the old sections pole or tower, especially IF you will first sign off on a binding personal injury and/or incidental property damage liability waiver.  If you are not willing to do this then you don’t have any business being on their property asking or begging for stuff in the first place (my opinion). 
 
And if they do want to keep the first two sections or so in tact it is usually just so they can get up on the rooftop if and when they need to.  So then it turns out to not be that big a removal deal anyway.
 
Anyway, that’s how I do it.  And I find that I can buy all the equipment, serviceable towers and antennas (most of which are no longer available if you did want to buy them) that I want and at a greatly reduced price as compared to having to pay the current prices of new stuff.
 
Step 2.   Step two is primarily concerning yourself with the proper and safe methods of detaching and lowering the old antenna system and the safe methods of disassembling and lowering the old tower assembly.
 
Rule # one is to never, ever start up any sectioned pole assembly or tower without checking to make sure that it is safe to climb in the first place. 
 
Check the base and make certain that the legs are not rusted out.  If they are they are first going to have to be safely re-secured in some fashion such as metal splinting or welding.  You may also have to use an additional two, three or four point supporting rope tie off to make the climb safe.
 
Also check to see if the tower is attached to the structure (or ever was) or if it is free-standing.  If there are signs that it was attached at some earlier time you will need to temporarily re-attach it to the structure to stiffen up the entire height of the structure, especially the first twenty feet or so.
 
Check if there are any guyed wire connections visible and if there are, are they broken, slack or still taunt.  If you can, put them back and/or tighten them back up as much as possible, depending upon the old wires condition. 
 
Look closely and see if there are ANY WIRES WHATSOEVER anywhere near where your body is going to be going up or anywhere near where you will be sending the antenna assembly or its parts down to the ground.  If there are and if you even suspect that they might be hot either re-evaluate your climb and/or use extreme caution! 
 
After you have made certain of all of these important observations, then and only then should you consider climbing. 
 
Rule # 2 is twofold.   NEVER climb a pole or tower structure without having at least one competent ground man there with you AT ALL TIMES and above all NEVER EVER ALLOW ANYONE TO CLIMB ANY TOWER WITHOUT WEARING A COMPLETELY SERVICEABLE, PROFESSIONAL CLIMBING BELT!  Climbing belts can get a little pricey but don’t necessarily have to be, and ANY climbing belt is cheaper to invest in than the ever possible physical pain and damage or hospital bills and related expenses based on stupidity, if you live, that is.
 
Before you start your climb make sure that you have at least one and maybe even two thin and lightweight but strong cotton “clothesline” type tie ropes attached to one of the rings on your climbing belt.  It (they) need to be at least twice as long as your’ climbing apex is going to be.  They will be used to raise and lower your work tools and to lower the antenna(s) down safely.
 
Most all ground plane antenna systems weigh in at well less than twelve pounds so the lightweight cotton rope will work perfectly.  It will provide both good hand grip and it won’t cut into your hands like plastic rope is prone to do.
 
It is also an excellent idea to tie on two or three 3’ lengths of cotton rope onto your belt to tie ANYTHING ELSE off with once you are up to your first (usually the highest) working height.
 
Your working tools can number anywhere from just a hammer, a few combination wrenches and a side cutting pair of pliers to a partial socket set, cotton or leather gloves, a hacksaw or maybe even a battery powered “Sawzall”, a battery powered drill with several drill bits, one or more screw drivers, plastic tie wraps, black tape and many other things which will be in the medium size plastic bucket tied on to your first long cotton rope. 
 
Note:  For a complete list of possible hand tools which you can build up an antenna/tower removal kit please see the glossary. 
 
Quite often you will literally have to work your way UP a tower by disconnecting, unbolting, moving and/or removing one or more (usually) smaller antenna systems such as television UHF V Traps or Yagis or FM radio receiving antennas and their wiring or whatever else might have been hung up there.  You will find these shorter lengths useful in either tying these smaller antennas over out of you way or the longer lengths of rope to start sending them down to your ground man.
 
At whatever height you are working ALWAYS securely tie yourself onto the tower assembly!   And never work at any height if there is any dangerous amount of swaying taking place on the tower while you are on it.  Come down immediately and re-secure the tower.  And don’t re-climb it until you do!  
 
Almost any smaller antennas which have been in place for several years are going to be rusted in place.  The easiest way to get them loose in one piece is to cut thru the center of the mounting bolts if you can get to there.  If you can’t it’s easier to cut the nuts off of the bolts instead of the other way around and it will do less damage to the antenna and its mounting hardware if you do so.
 
Lowering each of these smaller antennas first as you work your way up will clear the way for you reach, tie on to and start disassembling (if necessary) any of your larger antenna systems and beginning to slowly and carefully lower them to your ground man. 
 
Sometimes the removal of one (or possibly two) horizontal radial(s) will allow you to lower it directly down the side of the building and the tower without having to attach your second long rope and having the ground man have to hold it off and out and keep it from making any contacts as it comes down which might cause any property damage or damage to your antenna.
 
Be sure to send all of the tools in your bucket (and everything else loose) down before you start coming down from your climb.
 
Step 2 also concerns the removal of the tower itself.  I have already covered the pre-climb information pertaining to making the tower safe to climb.  Most towers are of two distinct types. 
 
One brand (and type) is Rohn and is a premium quality (and much more expensive) tower.  All others pretty much fall into a construction category know as “ladder” type.
 
Rohn brand tower is still available and is mostly sold in two sizes.  Both sizes are similarly constructed using extremely rugged, large diameter ¼” (and larger) solid steel, welded wire for both the steps and its zig-zag method of construction.  All of the ladder types of tower use approximately 1” round tubing for their steps.  Rohn is by far the better choice for strength and for all weather endurance.  Just about all types and brands of the old ladder type tower are now obsolete and are not readily available.  This is sort of a shame in as the ladder type towers are perfectly fine for just about anything up to fifty feet in height and they are much easier to climb and stand on than is the Rohn tower’s horizontal/angle type wire construction method. 
 
All communications tower assembles pretty much the same way, using three nut bolt assemblies at either end.  The bolt/nut sets are usually around 9/16”.  There are approximately twelve sets of these bolt/nut set on a fifty foot + /- tower.  You will be replacing all of these with new product of the same size and lengths unless you find that the pre-existing thru-holes in the tower sections have to be drilled out to a larger diameter (to tighten up the tower sections join) because of excessive wear. 
 
Anytime that you are assembling or disassembling communications tower sections it is highly recommended that you use a high quality “Gin” Pole.  (See glossary for image of …)
 
A Gin Pole is a device, usually homemade, which is slightly longer than one ten foot section length of tower.  It attaches to a/the lower tower section’s leg and extends approximately one or two feet up above the section to which it is attached.  It is primarily used to support the full weight of the section being removed and to make the removal as safe as possible.  The average weight of any tower section usually runs around 22# +/-.  Manhandling a ten foot length of tower into or out of place without using a Gin Pole is possible, but really pretty stupid.  It shows what kind of a man you are if you CAN do it, and it definitely shows what kind of a man you are if you CAN’T!  The possibilities of collateral damage can be very high and very expensive and the risk of serious injury to the climber (experienced or not) as well as the added considerable risk of danger placed on his ground crew is totally uncalled for.
 
Obviously the removal of a tower section starts at the top and you work your back down to the ground.  That is unless you are financially solvent enough and able to locate a lift bucket type truck, such as the types that perform tree trimming operations.  If you can get a bucket lift type truck in to the proper position and for an hour or two’s rental you can hook the bucket up somewhere above center height, cut 2 ½ of the legs all the way thru (and to the backside respectively) at ground level and lower the entire tower assemble down to the ground with the bucket where you can safely disassemble it at your convenience.
 
Assuming that you either can’t afford to, don’t want to or are not physically able to get a truck in close enough to your removal site, that brings us back to using a Gin Pole.
A really good quality Gin Pole will be at least 1 ½”+ in diameter and will use either a really good quality 5/8”+ woven hemp rope or a plastic woven rope of a similar size.  Hemp is desirable and is much easier on the gloved  or ungloved hands.  It is also preferable to plastic in flex even if it might tend to stretch out a little more.
A really good quality Gin Pole will be at least 1 ½”+ in diameter and will use either a really good quality 5/8”+ woven hemp rope or a plastic woven rope of a similar size.  Hemp is desirable and is much easier on the gloved  or ungloved hands.  It is also preferable to plastic in flex even if it might tend to stretch out a little more.
 
The tools that are most commonly used “up there” are:  up to two 10” or +  in length combination wrenches having the proper end sizes,  a ½” or 3/8ths” ratchet/socket set  with up to two of the correct sockets, a 2# hammer, a 3’ crowbar and a can of penetrating oil or WD40.  (See Glossary for a complete list of my tool kit)
 
However if you run into a tower that is in really bad condition or which has been slightly twisted by the wind you may also need a good heavy duty mechanical screw or scissors jack or a medium size/weight hydraulic hand pump jack, any of which will require a minimum of six to eight inch lift, and two to four good, heavy duty SOLID 12”x 1 or 2” x 4” wood planks and 12” 2 x 4 saw offs to place both above the lower tower section’s uppermost rungs and below the top tower section’s lowest horizontal rungs.
 
Again, dismantling a tower does not require “Rocket Science” but I had had a few towers that were so firmly wedged or twisted and tightly stuck together that we literally had to hook the Gin Pole’s rope to a 6000# winch on the front of the jeep to put enough lift pressure on the top section WHILE the climber was beating on the unbolted, oiled connection with a ten pound sledge before it finally broke loose and came off and up just as pretty as any missile launch you’ve ever seen on television.  Each removed section is lowered to the ground by the ground man, not the climber.  Then the rope is sent back up to the climber to be reattached to the top of the next section which is to be removed.  The Gin Pole is then lowered to the same approximate positioning on the next lower tower section coming and is firmly reattached again.  And so on until you are down to your last two sections.   Remove the horizontal tie-in bracket from the house or structure and from the second tower section pole at this time (never before).
 
The last ground section can be a little surprising sometimes.  It may not even be a full length section (at least not above ground level).   You may start Sawzall’ing off the legs at ground height and find that the equivalent of a gallon or more of really nasty water will start pouring out where it has been trapped inside those legs for literally years.  And that is when you start re-examining the lower end of the sawed off section on the inside for excessive damage. 
 
Beat or saw off the three tower stubs down level with the concrete base or the bare ground and you are pretty much done except for loading up and hauling away your new (old) treasure.
 
Step 3 is your initial inspection and pre-clean.
Start with the tower sections and then check the antenna. 
 
This way you can store and put the tower assembly completely out of your mind for a while.  Check each of the tower sections for physical or excessive rust damage and make sure that you have removed all old clamping assemblies, antenna mounting brackets, any extraneous screws, eye screws or bolts which may have been installed by whomever and all old dried up plastic tape or wire wrappings or whatever else might have been previously attached.  I will discuss refurbishing the tower sections at a later date and in another article.
 
Now for the antenna assembly’s pre-clean and repair steps.
 
Obviously all of the aluminum sections and all related antenna pieces and all hardware have to be taken apart with as little additional damage as possible to properly pre-clean and/or make any serious repairs.  A lot of ground plane antennas used screws as opposed to constriction clamps and none of anything which was originally used was of very good quality.  Anything to save a buck, so to speak.  Most all of the communications antenna assemblies that I am familiar with used grade 2 metal hardware, again because it was the cheapest.  Sometimes this will work in your favor when you are disassembling your sections because they will break right in two after enough wrench or socket pressure is applied.  Then again sometimes they won’t and getting everything apart then while still keeping everything in good cosmetic and physical condition can be considerably more difficult.  This is what we are going to discuss here. 
 
In a perfect world and on a perfect day disassembly of a simple vertical radiator ground plane antenna should not be difficult at all.
 
But then again, when was the last time that YOU had a perfect day? 
 
The first thing to do is to get the horizontal elements off and out of the way.  Most horizontal element assemblies are either two or three sections long.  Almost all are secured together by either short ¼” screws or by external compression clamp assemblies.  All of the older compression type clamp assemblies used a saddle clamp with a screw/nut binder.  Some of the newer models use a fully circular constriction band type clamp which uses an external screw/worm binder.  The later is by far the best type to reuse on your refurbishment. 
 
Getting the old short screws which secure the sections out is pretty straight forward and if the screws were stainless they usually come out with a minimum of trouble or damage.  Most of these type screws were ferrous metal however and started rusting away the day they were first installed.  Steel screws and aluminum rods are a bad combination and additional damage was occasionally done to the aluminum rods in the holes areas as a result, the amount and extent of damage to either or both determined by the length of time that they were joined.
 
If the screw has a screwdriver slot type head don’t use it.  Always use a small ignition wrench (preferably the closed end), a ¼” ratchet/and socket or a ¼” nut driver.  And always presoak the screw with any type of medium viscous oil, motor oil, WD40 or penetrating oil to help dissolve any rust and/or oxidized aluminum residue or buildup that you can. 
 
If the screw head breaks off you still have a few options depending upon your level of patience and your time restraints.  You can try to pull the sections apart regardless and if there is only a very small amount of raised broken screw the sections will come apart.
 
If the screw’s damage is significant you can very carefully use a “Dremel” type tool with a metal or stone bit on a low to medium speed setting to remove more of the obstruction. 
 
A small mill file or even the edge of a larger file will also work to cut the damaged screw obstruction down to where the sections can be separated. 
In a worst case scenario you may have to file on the damaged screw until you have flushed the entire screw body with the curved surface of the inner rod in which it remains seized.  This will cause cosmetic damage to the outer rod in that holes immediate area but it can be turned 180 degrees and new thru holes of the correct diameter can be re-drilled.
 
As for the remaining seized screw body in the smaller rod you must perform the same 180 degree re-drill but it will not show or cause any problems with either the reassembly or the operation of your element assembly.
 
Disassembly of a similarly screw/pinned vertical radiator is exactly the same.
 
When you encounter the older external saddle clamp assembly and it will not come off using its original screw/nut you can use a saw type tool to cut the screw completely thru at its middle.  You can use a short hack saw blade (with or without a hacksaw frame), a reciprocating hydraulic air/saw tool, a suitability sized pair of good quality long handled side cutters, a 14 to 16” pair of bolt cutters or even one edge of a smaller triangle file.
 
Just use caution not to bear down with too much weight regardless of what type tool you use.  If you press down too firmly when the tool goes thru the screw body you will put a healthy diagonal saw mark in your aluminum rod section.  Again, this should be cosmetic damage only and will not harm the efficiency of your antenna assembly IF you don’t damage it to extremes.  You can try to place a narrow, thin metal shim between the tube and the screw to be cut.  If you can work it in there this will eliminate damage to your tube by a saw blade or whatever you use. 
 
You should not experience any major difficulties whatsoever separating your rod sections if they utilized the second type of external constricting clamp.  The newer, fully circular constriction band type clamps which use an external screw/worm binder are “generally” constructed of stainless steel and rarely fail unless they have been over tightened and damaged or weakened from excessive torque.  But whether they are of stainless steel construction or not, they generally do not damage either of the rods.
 
Now that you have got the fasteners removed it’s time to separate the rod sections.  Again they should come apart without a lot of effort or trouble but if they ARE stuck and you can’t pull them apart by yourself find a friend and try again.  If the two of you can’t pull them apart apply whatever type oil or WD40 or penetrating fluid you can thru the empty screw holes and try again.  Use a back and forth twisting action between the two rods to help break them loose from their set.
 
If they still won’t budge lay the rods down with the join on top of a wooden surface or short section of 2x4 and apply a constant tapping pressure to the rods while you rotate them on the board.
 
If THIS doesn’t work ether I then pad up the jaws of a good vise and insert one of the seized rod sections about six inches from the join and tighten the vise down enough to secure it but not to deform it.  I then again tap around the join and as a last resort try to pull the free rod section out of the vise’d section.
 
If THIS doesn’t work ether I then pad up the jaws of a good vise and insert one of the seized rod sections about six inches from the join and tighten the vise down enough to secure it but not to deform it.  I then again tap around the join and as a last resort try to pull the free rod section out of the vise’d section.
 
If none of these methods work even after repeated oiling and soaking and retrying then I try applying heat from first a hand held Propane or Mapp gas cylinder and re-tap the join repeatedly again.
 
As a last resort I use a flaring tip on an oxyacetylene torch to reheat the join and try to carefully (HOT!) separate it again.  If all of this fails after repeated attempts I cut the join out of the pieces and use them for later unintended uses.
 
As a last resort I use a flaring tip on an oxyacetylene torch to reheat the join and try to carefully (HOT!) separate it again.  If all of this fails after repeated attempts I cut the join out of the pieces and use them for later unintended uses.
 
Obviously, you won’t be in a position to do this having limited amounts of tubing but the good news is that this has only happened to me two or three times out of several hundreds of attempts.  And even if you DO have to physically shorten any particular aluminum section you can usually regain the required overall  height or length in either the vertical or horizontal assemblies by slightly extending and remarking the other adjoining sections’ visible exposures.
 
In a worst case scenario you’re simply going to have to locate replacement aluminum sections.
 
A cursory inspection of all aluminum rods, related parts, wires, bolts, screws and plastic parts needs to be made now to determine which individual pieces will need to be replaced or repaired as a result of having been lost, damaged or broken during the usage of the antenna assembly.
 
Disassembly of a similarly clamped vertical radiator is exactly the same. 
 
However, completely disassembling the lower vertical radiator section is quite a bit more complicated.
 
The lower section assembly of the vertical radiator on the Penetrator 500 (The M1 or the V1, whichever you choose to call it) IS the heart and soul of the whole antenna assembly.  It consists of the following parts and pieces:  The M1 mast pole which is either 77” or 71” respectively, and depending upon when the assembly was made and marketed by Hy-Gain, the upper and lower horizontal element bracket plates (2), the upper plastic insulator, the lower plastic insulator which also includes the power wire assembly, the aluminum mounting bracket which also includes the SO-239 connector, the matching “rod” wire which sets the antenna to the proper frequency and the beta “rod” wire or “shunt” which sets the antenna to operate at the proper Ohmage.
 
Here is how I take it apart: 
 
I start by removing the M1 mast pole’s lower, horizontal thru screw/nut assembly.  It is a ferrous metal screw and the thru-hole in the lower plastic insulator is oversized and not threaded.  After it is removed this allows the removal of the (usually) 71” pole and cuts your overall work area down to about 14 vertical inches or so.
 
Assuming that the eight ¼” vertical thru-bolt/nut assemblies have already been removed when you removed the horizontal radial assemblies …
 
I unbolt the three vertical inner ¼” bolt/nut assemblies which secure the upper and lower horizontal mounting plates and the upper plastic insulator to the mounting bracket.  These two pieces and the upper insulator will then come loose.  I discard all of the old bolt/nut assemblies after taking an overall measurement of all fastening materials.
 
Then I hand hold or vise mount the mounting bracket right side up and drill off the four larger rivet’s flared bottoms which are installed upside down and which secure the lower plastic insulator (You only need to use a slightly larger diameter drill bit than is the total diameter of the flared rivet bottom in your drill.
 
Once you cut off the flared rivet bottom the rivet itself is then perfectly straight and can be punched out).  I then drive these four rivets out thru the mounting bracket with a ¼” flat tipped metal punch and a small to medium weight ball peen hammer. 
 
Then I turn the mounting bracket upside down, re-vise it and then drill off the four smaller rivet bottoms which secure the SO-239.  Again, I drive these four remaining rivets out of the mounting bracket in the exact same manner.  Then I cut the power wire off at the top of the SO-239 to separate it from same.
 
You are done with your disassembly.
 
I use stainless steel screw/nut sets of the appropriate size and lengths to replace the eight original rivets. I cut a 1 ¼” length of THHN sheathed 12 Gauge stranded copper wire and properly solder it to the new SO-239 to replace the original 18 gauge plastic sheathed wire which was removed.
 
I solder a closed ring end terminal of the appropriate sizes to the other end of the new 1 ¼” wire.
 
I replace all ferrous metal fastening hardware with 10-24 Gauge/thread brass materials when re-assembling the lower insulator package to eliminate any future corrosion problems in the power wire assembly.  Everything goes back together bolt/nut connected and (red strength) Loc-tite’d to prevent any future loosening.  This includes the eight replacement stainless steel screw/nut assemblies used to replace the original rivets.
 
Step 4.  The replacement or repair of any missing and/or damaged or unusable parts of the antenna system comes next.
 
A simple hands on and visual examination of all aluminum rods, tubes and related parts and/or hardware will reveal if any of them have been damaged as a result of deterioration, improper assembly or installation, weather or site related causes or simple acts of God type events, and if any of these parts need to be reordered, replaced, rebuilt or straightened. 
 
One of the first things I look for is any missing parts whatsoever.  Then I look for damaged related metal or plastic parts.  Then I examine all of the aluminum tubes and rods for proper length, soundness, straightness.  If they aren’t the proper length which was originally called for or if they are rot damaged from the inside then they usually are not worth reusing, much less straightening.
 
The first two checks are made by measurement and by visual inspection and the third is by manually rolling the tubes and rods.  Following the first two checks I decide which pieces might need to be repurchased (if still available), which pieces might need to be straightened or heli-arc’ed, re-welded, or re-fabricated.  I then get those pieces reordered or start the relocation and reacquisition process of whatever pieces I need.
 
Then I inspect the tubes and rods for true and straightness.  The only thing needed to do this is a large, perfectly flat area where you can roll the rods to check for wind curves or slight bends.  It is helpful if this area is clean, very smooth and openly exposed or well lit.  The good lighting helps me to see and watch the thin,” high shine” line of light that is reflected off from the side of a tube or rod from one end to the other.  If this line stays smooth while rolling the piece very little or no bends are found.  If the piece jumps up and down in any area or if the “shine line” wavers then the rod will require attention. 
 
Note:  Because of the large amounts of detailed information involved in re-working the following pieces and the fact they all require an individual jig (at least the way I build them) I will not cover my re-straightening and/or truing procedure of the aluminum tubes and/or rods in this article.  Nor will I cover the re-fabrication of the matching rod, the beta rod or the top hat anti-static wires.  Nor will I cover the re-working of the new replacement lower plastic insulator.  I will cover each of these topics completely in the near future as a closely associated treatise.
 
Step 5.  Now that the reusable rods have been identified they need to be highly cleaned and prepped on the end areas of their inside surfaces and on their total outside surface areas to insure the completely efficient continuity of electrical flow.
 
This can be accomplished in many different ways using many different methods which run from the simple to the extreme.  While the end result is always the same the amount of time and effort (and resources) one has available will determine the final methodologies.
 
Some of the equipment and tools which I use are simple and straight forward.  Some are not. I started out cleaning galled aluminum rods with a good quality soap pad such as SOS or Brillo.  They do work fairly well but they are tedious, sloppy, and extremely tiresome and they will wear you out quickly.  So will steel wool.
 
I have also used abrasive sandpaper or wet/dry sheets.  These will cut thru much more accumulated external residue buildup quicker and easier but they don’t leave as good or as smooth a finish on the aluminum as the soap pads do.
 
What I primarily use to clean just about anything including aluminum rods is a modified four foot wide bead blast cabinet and a homemade 1” x 36” electric powered, abrasive belt sander. 
 
The bead cabinet is modified so that I can pass any diameter or length rod of any type completely thru it from either side.  This enables me to quickly and completely clean any rod or pipes entire exterior surfaces as well as approximately 6” up inside each end with very little effort and in a very short period of time.
 
The abrasive belt sander is powered by a ¼ Hp electric motor and has a three position hardwired reversible direction on-off switch.  The belt’s surface is constructed of a synthetic material which is rough to the touch but does very little damage to the exterior surface of aluminum rods (in particular) and it delivers a very pleasing semi-satin finish to the metal which looks great (again, my opinion).  That finish is fine enough that if I wish to do so I can spend a few additional hours more time and hard buff the tube(s) on a pair of 8” combination wheels and attain a very hard mirror finish which almost rivals chrome.
 
I know, WHO CARES about a hard shiny finish on a communications antenna especially since they don’t ever come that way from the factory?
 
YOU SHOULD! 
 
Your antenna’s entire electrical signals transmission and propagation patterns run and rely on the exterior surfaces of the vertical radiator and the horizontal element assemblies.  When they are clean and your joins are properly made and watertight the antenna will deliver its optimum performance capabilities.  When antennas age and gall up on the outer surfaces or when the rod sections slip and/or become loosened you will lose considerable electrical continuity and nothing works quite right.
 
While I understand that anyone can or could go to this amount of trouble to refurbish their aluminum tubes and rods I also realize that most of you will not.  It is a true chore to go to these extremes and while all of the necessary and specialized equipment necessary to do this can be found at any good machine shop most folks simply won’t devote that much time, trouble or expense to the effort.
 
Step 6.  Now we are at the reassembly and final testing phase of the project.
 
I only use IDEAL brand, stainless steel external compression clamps on all of my antenna projects.  The original Penetrator 500 requires twelve different clamps of four different opening diameters.  From large to small you will need one # 5016 clamp, one # 5010 clamp, five # 5006 clamps and five # 6202 (old #) or 6204 (new #) clamps. 
 
The later Penetrator 500 model and the Super Golden Penetrator 500 require four less clamps.  You will only need one of the # 5006 clamps because of their two piece horizontal radial assemblies, as opposed to the original configuration’s three piece radial assemblies. 
 
The IDEAL brand clamps are available at almost all of the better known, nationwide auto parts houses.  I buy mine in bulk supply from O’Rileys Auto Parts.
I begin my reassembly by measuring out the required or recommended exposed lengths of the vertical radiator’s M2, M3, M4 and M5 sections with a good quality steel tape measure.  Then I mark these precise lengths with an indelible ink, fine pointed “Sharpie” brand marking pen.  A dot will do.  Then I insert that particular rod into the larger, lower vertical rod section to that mark and temporarily secure it at its proper length with one of the correctly sized new IDEAL clamps. …
 
IMPORTANT NOTE: There is a correct way to install any compression clamp on adjoining antenna rods and/or tube sections.  The body of the external screw assembly should always be centered from left to right on the length of the tube’s compression slit and it should also be centered directly above the compression slit.  This will allow the clamp to compress to the necessary torque pressure without damaging either it or the rods or tubes. 
 
Then I scribe a complete circular mark all the way around the original rod.  I loosen the clamp enough to remove the marked rod then I retighten the new clamp snugly but not tightly and leave it attached and properly positioned to its proper rod for later final assembly.
 
I then repeat this procedure with all three sections of each of the remaining horizontal rod assemblies. 
 
When I am ready for final assembly I rotate all five sections of the vertical radiator to the points where all four of the newly installed IDEAL clamps line up exactly vertically.  I try to place the clamps at the nine o’clock position on the tubes when looking at the antenna from the front.  I do this so that at any time after reinstallation I can simply stand directly below the assembly, look straight up past the base section of the radiator to its tip and I can tell if anything has slipped or moved.  If they don’t remain vertically in-line something has slipped because of improper tightening or from wind or ice load or whatever and it is instantly noticeable.
 
I then do the exact same thing to each of the reassembled horizontal element assemblies using the 270 degree mark so that all of the clamp screws are on the left side and pointed straight up.
 
Note:  The following step is being presented pretty much “tongue in cheek” so to speak, but you REALLY, REALLY DO NEED TO PAY VERY CLOSE ATTENTION to its overall content.  IT COULD JUST SAVE YOUR OR A CLOSE FRIENDS LIFE!
 
When I finally get to the final testing phase of the project I sometimes use a dedicated rig (a Cobra 2000 XL), a 50’ dedicated 50’ length of excellent quality and condition Belden RG-213 coaxial cable, and a dedicated WAWASEE brand, “Black Cat” Model # 1002 FC/M combination RF/SWR meter. 
I make ALL of my vertical adjustments at the M1/M2 section of the vertical radiator.  The horizontal element assemblies get no additional adjustments except to insure that they all measure out to exactly 105” (full quarter wavelength).
 
Sometimes when I’m bored or just growing tired of life I like to invite a friend or two over both to assist and to make fun of me.  Since my facilities require using both inside and outside locations I like to use one person on the rig, a second person in the shop doorway relaying the adjustments information and the ”fool” (that’s me) on the stepladder at the antenna’s base.  I’m the one who’s going to get the ever lovin’ $%!+  knocked out of him if everybody isn’t on the same page and paying rapt attention!.  But it seems to work out quite well in the end.  Most of the time!
 
Far and away the definitely better and more desirable way of testing for and determining the proper frequency or center bandwidth acquisition and the related SWR adjustments is by using a good quality antenna SWR meter.  I own and use a MFJ 257B instrument.  Dedicated antenna SWR meters are expensive but they will set your antenna to the optimum specifications very quickly and very easily as compared to the aforementioned and time consuming “dedicated everything” method.  Not to mention the fact that using this method is a whole lot safer! 
 
If you don’t own or have access to one of these meters you are probably going to be using method # one.  Just be careful and pay attention.  You can’t afford to be wrong.  Not even once!  If you don’t feel comfortable doing things this way, stop right where you are and get qualified answers, advice and/or assistance.
 
Just Remember … Regardless of whatever method or type of testing equipment you use:
 
YOU CAN’T BE TOUCHING THE DAMN ANTENNA ASSEMBLY ANYWHERE WHATSOEVER WHEN THE MAN ON THE RIG HAS THE DAGGONE THING KEYED UP!!!  IF IT WILL LIGHT UP A FOUR FOOT 110 VOLT FLOURESCENT LIGHT TUBE SIMPLY BY TOUCHING OR ATTACHING IT TO THE VERTICAL MAST IT WILL SURE AS HECK DO THE SAME TO YOU, OR MUCH WORSE!
 
Step # 7:  The safe and effective reinstallation of your newly refurbished antenna system is the exact opposite of step # 2.  Just take your time.
 
I hope that you have found this article to be somewhat entertaining and that it may have fostered some ideas and/or insights into any final formulation of your own plans or methods of being capable of accomplishing the same acts if so desired.
 
 
Thank you for reading my article,
 
Jim Dent
1/29/2011
 
      
Note:  Glossary Pending:  Image of an installed Penetrator 500, List of antenna & tower removal tools in kit, image of a Gin Pole image of rod grinder, image of bead cabinet
 
 
 
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Article Three:  Decibel
                         From Wikipedia, the free encyclopedia
 
 
This article is about the term Decibel as used in a ratio of electrical measures.
Portions of this article which are pertinent and/or related to citizens band radio applications have been hi-lighted.
 
 
The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. [1] Being a ratio of two measurements of a physical quantity in the same units, it is a dimensionless unit. A decibel is one tenth of a bel, a seldom-used unit.
 
The decibel is widely known as a measure of sound pressure level, but is also used for a wide variety of other measurements in science and engineering, most prominently in acoustics, electronics, and control theory. In electronics, the gain of amplifiers, attenuation of signals, and signal to noise ratios are often expressed in decibels. It confers a number of advantages, such as the ability to conveniently represent very large or small numbers, a logarithmic scaling that roughly corresponds to the human perception of sound and light, and the ability to carry out multiplication of ratios by simple addition and subtraction.
 
The decibel symbol is often qualified with a suffix, that indicates which reference quantity or frequency weighting function has been used. For example, dBm indicates that the reference quantity is one milliwatt, while dBu is referenced to 0.775 volts RMS. [2] and dBμV/m referenced to microvolts per meter for radio frequency signal strength.
 
The definitions of the decibel and bel use logarithms to base 10. The neper, used in electronics, uses natural logarithm to base (e).
 
Contents
 
1 History
• 2 Definition
o 2.1 Power quantities
o 2.2 Field quantities
o 2.3 Examples
• 3 Merits
• 4 Uses
o 4.1 Acoustics
o 4.2 Electronics
o 4.3 Optics
o 4.4 Video and digital imaging
• 5 Common reference levels and corresponding units
o 5.1 Electric power
o 5.2 Voltage
o 5.3 Acoustics
o 5.4 Audio electronics
o 5.5 Radar
o 5.6 Radio power, energy, and field strength
o 5.7 Antenna measurements
o 5.8 Other measurements
• 6 See also
• 7 References
• 8 Further reading
• 9 External links
 
History
 
The decibel originates from methods used to quantify reductions in audio levels in telephone circuits. These losses were originally measured in units of Miles of Standard Cable (MSC), where 1 MSC corresponded to the loss of power over a 1 mile (approximately 1.6 km) length of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and roughly matched the smallest attenuation detectable to an average listener. Standard telephone cable was defined as "a cable having uniformly distributed resistances of 88 ohms per loop mile and uniformly distributed shunt capacitance of .054 microfarad per mile" (approximately 19 gauge). [citation needed]
 
The transmission unit (TU) was devised by engineers of the Bell Telephone Laboratories in the 1920s to replace the MSC. 1 TU was defined as ten times the base-10 logarithm of the ratio of measured power to a reference power level. [3] The definitions were conveniently chosen such that 1 TU approximately equaled 1 MSC (specifically, 1.056 TU = 1 MSC). [4] Eventually, international standards bodies adopted the base-10 logarithm of the power ratio as a standard unit, named the bel in honor of the Bell System's founder and telecommunications pioneer Alexander Graham Bell. [5] The bel was larger by a factor of ten than the TU, such that 1 TU equaled 1 decibel. [6] For many measurements, the bel proved inconveniently large, giving way to the decibel becoming the common unit of choice.
 
In April 2003, the International Committee for Weights and Measures (CIPM) considered a recommendation for the decibel's inclusion in the International System of Units (SI), but decided not to adopt the decibel as an SI unit. [7] However, the decibel is recognized by other international bodies such as the International Electrotechnical Commission (IEC). [8] The IEC permits the use of the decibel with field quantities as well as power and this recommendation is followed by many national standards bodies, such as NIST, which justifies the use of the decibel for voltage ratios.[9]
 
Definition
 
A decibel (dB) is one tenth of a bel (B), i.e. 1B = 10dB. The bel is the logarithm of the ratio of two power quantities of 10:1, and for two field quantities in the ratio. [10] A field quantity is a quantity such as voltage, current, sound pressure, electric field strength, velocity and charge density, the square of which in linear systems is proportional to power. A power quantity is a power or a quantity directly proportional to power, e.g. energy density, acoustic intensity and luminous intensity.
 
The calculation of the ratio in decibels varies depending on whether the quantity being measured is a power quantity or a field quantity.
Power quantities
 
When referring to measurements of power or intensity, a ratio can be expressed in decibels by evaluating ten times the base-10 logarithm of the ratio of the measured quantity to the reference level. Thus, the ratio of a power value P1 to another power value P0 is represented by LdB, that ratio expressed in decibels, which is calculated using the formula:
 
P1 and P0 must measure the same type of quantity, and have the same units before calculating the ratio. If P1 = P0 in the above equation, then LdB = 0. If P1 is greater than P0 then LdB is positive; if P1 is less than P0 then LdB is negative.
Rearranging the above equation gives the following formula for P1 in terms of P0 and LdB:
.
Since a bel is equal to ten decibels, the corresponding formulae for measurement in bels (LB) are
 
Field quantities
 
When referring to measurements of field amplitude it is usual to consider the ratio of the squares of A1 (measured amplitude) and A0 (reference amplitude). This is because in most applications power is proportional to the square of amplitude, and it is desirable for the two decibel formulations to give the same result in such typical cases. Thus the following definition is used:
 
This formula is sometimes called the 20 log rule, and similarly the formula for ratios of powers is the 10 log rule, and similarly for other factors. [citation needed] The equivalence of  and  is one of the standard properties of logarithms.
The formula may be rearranged to give
 
Similarly in electrical circuits dissipated power is typically proportional to the square of voltage or current when the impedance is held constant. Taking voltage as an example, this leads to the equation:
 
where V1 is the voltage being measured, V0 is a specified reference voltage, and GdB is the power gain expressed in decibels. A similar formula holds for current.
 
Merits
 
The use of the decibel has a number of merits:
• The decibel's logarithmic nature means that a very large range of ratios can be represented by a convenient number, in a similar manner to scientific notation. This allows one to clearly visualize huge changes of some quantity. (See Bode Plot and half logarithm graph.)
• The mathematical properties of logarithms mean that the overall decibel gain of a multi-component system (such as consecutive amplifiers) can be calculated simply by summing the decibel gains of the individual components, rather than needing to multiply amplification factors. Essentially this is because log(A × B × C × ...) = log(A) + log(B) + log(C) + ...
• The human perception of the intensity of, for example, sound or light, is more nearly proportional to the logarithm of intensity than to the intensity itself, per the Weber–Fechner law, so the dB scale can be useful to describe perceptual levels or level differences.
 
Uses
 
Acoustics
 
Main article:  Sound pressure
 
The decibel is commonly used in acoustics to quantify sound levels relative to a 0 dB reference which has been defined as a sound pressure level of .0002 microbar.[11] The reference level is set at the typical threshold of perception of an average human and there are common comparisons used to illustrate different levels of sound pressure. As with other decibel figures, normally the ratio expressed is a power ratio (rather than a pressure ratio).
The human ear has a large dynamic range in audio perception. The ratio of the sound intensity that causes permanent damage during short exposure to the quietest sound that the ear can hear is greater than or equal to 1 trillion.[12] Such large measurement ranges are conveniently expressed in logarithmic units: the base-10 logarithm of one trillion (1012) is 12, which is expressed as an audio level of 120 dB. Since the human ear is not equally sensitive to all sound frequencies, noise levels at maximum human sensitivity—somewhere between 2 and 4 kHz—are factored more heavily into some measurements using frequency weighting. (See also Stevens' power law.)
Further information: Examples of sound pressure and sound pressure levels
 
Both the decibel and the bel can be used to represent acoustic noise power levels in hard drive specifications.[13] The symbol 'B' for bel may be confused with the same symbol for the byte, though hard drives are typically measured in larger units such as the gigabyte.
 
Electronics
 
In electronics, the decibel is often used to express power or amplitude ratios (gains), in preference to arithmetic ratios or percentages. One advantage is that the total decibel gain of a series of components (such as amplifiers and attenuators) can be calculated simply by summing the decibel gains of the individual components. Similarly, in telecommunications, decibels are used to account for the gains and losses of a signal from a transmitter to a receiver through some medium (free space, wave guides, coax, fiber optics, etc.) using a link budget.
 
The decibel unit can also be combined with a suffix to create an absolute unit of electric power. For example, it can be combined with "m" for "milliwatt" to produce the "dBm". Zero dBm is the power level corresponding to a power of one milliwatt, and 1 dBm is one decibel greater (about 1.259 mW).
In professional audio, a popular unit is the dBu (see below for all the units). The "u" stands for "unloaded", and was probably chosen to be similar to lowercase "v", as dBv was the older name for the same thing. It was changed to avoid confusion with dBV. This unit (dBu) is an RMS measurement of voltage which uses as its reference 0.775 VRMS. Chosen for historical reasons, it is the voltage level which delivers 1 mW of power in a 600 ohm resistor, which used to be the standard reference impedance in telephone audio circuits.
 
Optics
 
In an optical link, if a known amount of optical power, in dBm (referenced to 1 mW), is launched into a fiber, and the losses, in dB (decibels), of each electronic component (e.g., connectors, splices, and lengths of fiber) are known, the overall link loss may be quickly calculated by addition and subtraction of decibel quantities.
 
In spectrometry and optics, the blocking unit used to measure optical density is equivalent to −1 B.
 
Video and digital imaging
 
In connection with digital and video image sensors, decibels generally represent ratios of video voltages or digitized light levels, using 20 log of the ratio, even when the represented optical power is directly proportional to the voltage or level, not to its square. Thus, a camera signal-to-noise ratio of 60 dB represents a power ratio of 1000:1 between signal power and noise power, not 1,000,000:1. [14] [15] However, as mentioned above, the 10 log convention prevails more generally in physical optics, so the terminology can become murky between the conventions of digital photographic technology and physics. Most commonly, quantities called "dynamic range" or "signal-to-noise" (of the camera) would be specified in 20 log dBs, but in related contexts (e.g. attenuation, gain, intensifier SNR, or rejection ratio) the term should be interpreted cautiously, as confusion of the two units can result in very large misunderstandings of the value. Photographers also often use an alternative base-2 log unit, the f-stop, and in software contexts these image level ratios, particularly dynamic range, are often loosely referred to by the number of bits needed to represent the quantity, such that 60 dB (digital photographic) is roughly equal to 10 f-stops or 10 bits.
 
Common reference levels and corresponding units
 
Although decibel measurements are always relative to a reference level, if the numerical value of that reference is explicitly and exactly stated, then the decibel measurement is called an "absolute" measurement, in the sense that the exact value of the measured quantity can be recovered using the formula given earlier. For example, since dBm indicates power measurement relative to 1 milliwatt,
• 0 dBm means no change from 1 mW. Thus, 0 dBm is the power level corresponding to a power of exactly 1 mW.
• 3 dBm means 3 dB greater than 0 dBm. Thus, 3 dBm is the power level corresponding to 103/10 × 1 mW, or approximately 2 mW.
• −6 dBm means 6 dB less than 0 dBm. Thus, −6 dBm is the power level corresponding to 10−6/10 × 1 mW, or approximately 250 μW (0.25 mW).
If the numerical value of the reference is not explicitly stated, as in the dB gain of an amplifier, then the decibel measurement is purely relative. The practice of attaching a suffix to the basic dB unit, forming compound units such as dBm, dBu, dBA, etc., is not permitted for use with the SI.[16] However, outside of documents adhering to SI units, the practice is very common as illustrated by the following examples.
[edit] Electric power
dBm or dBmW
dB(1 mW) – power measurement relative to 1 milliwatt. XdBm = XdBW + 30.
dBW
dB(1 W) – similar to dBm, except the reference level is 1 watt. 0 dBW = +30 dBm; −30 dBW = 0 dBm; XdBW = XdBm − 30.
 
Voltage
 
Since the decibel is defined with respect to power, not amplitude, conversions of voltage ratios to decibels must square the amplitude, as discussed above.
 
dBV
dB(1 VRMS) – voltage relative to 1 volt, regardless of impedance.[2]
dBu or dBv
dB(0.775 VRMS) – voltage relative to 0.775 volts.[2] Originally dBv, it was changed to dBu to avoid confusion with dBV.[17] The "v" comes from "volt", while "u" comes from "unloaded". dBu can be used regardless of impedance, but is derived from a 600 Ω load dissipating 0 dBm (1 mW). Reference voltage 
In professional audio, equipment may be calibrated to indicate a "0" on the VU meters some finite time after a signal has been applied at an amplitude of +4 dBu. Consumer equipment will more often use a much lower "nominal" signal level of -10 dBV.[18] Therefore, many devices offer dual voltage operation (with different gain or "trim" settings) for interoperability reasons. A switch or adjustment that covers at least the range between +4 dBu and -10 dBV is common in professional equipment.
dBmV
dB(1 mVRMS) – voltage relative to 1 millivolt across 75 Ω.[19] Widely used in cable television networks, where the nominal strength of a single TV signal at the receiver terminals is about 0 dBmV. Cable TV uses 75 Ω coaxial cable, so 0 dBmV corresponds to −78.75 dBW (−48.75 dBm) or ~13 nW.
dBμV or dBuV
dB(1 μVRMS) – voltage relative to 1 microvolt. Widely used in television and aerial amplifier specifications. 60 dBμV = 0 dBmV.
 
Acoustics
 
Probably the most common usage of "decibels" in reference to sound loudness is dB SPL, referenced to the nominal threshold of human hearing: [20]
 
dB(SPL)
 
dB (sound pressure level) – for sound in air and other gases, relative to 20 micropascals (μPa) = 2×10−5 Pa, the quietest sound a human can hear. This is roughly the sound of a mosquito flying 3 meters away. This is often abbreviated to just "dB", which gives some the erroneous notion that "dB" is an absolute unit by itself. For sound in water and other liquids, a reference pressure of 1 μPa is used. [21]
 
dB(PA)
 
dB – relative to 1 Pa, often used in telecommunications.
 
dB SIL
 
dB sound intensity level – relative to 10−12 W/m2, which is roughly the threshold of human hearing in air.
 
dB SWL
 
dB sound power level – relative to 10−12 W.
 
dB(A), dB(B), and dB(C)
 
These symbols are often used to denote the use of different weighting filters, used to approximate the human ear's response to sound, although the measurement is still in dB (SPL). These measurements usually refer to noise and noisome effects on humans and animals, and are in widespread use in the industry with regard to noise control issues, regulations and environmental standards. Other variations that may be seen are dBA or dBA. According to ANSI standards, the preferred usage is to write LA = x dB. Nevertheless, the units dBA and dB(A) are still commonly used as a shorthand for A-weighted measurements. Compare dBc, used in telecommunications.
 
dB HL or dB hearing level is used in audiograms as a measure of hearing loss. The reference level varies with frequency according to a minimum audibility curve as defined in ANSI and other standards, such that the resulting audiogram shows deviation from what is regarded as 'normal' hearing. [citation needed]
 
dB Q is sometimes used to denote weighted noise level, commonly using the ITU-R 468 noise weighting [citation needed]
 
Audio electronics
 
dBFS
 
dB(full scale) – the amplitude of a signal compared with the maximum which a device can handle before clipping occurs. Full-scale may be defined as the power level of a full-scale sinusoid or alternatively a full-scale square wave.
 
dBTP
 
dB(true peak) - peak amplitude of a signal compared with the maximum which a device can handle before clipping occurs.[22] In digital systems, 0 dBTP would equal the highest level (number) the processor is capable of representing. Measured values are always negative or zero, since they are less than or equal to full-scale.
 
Radar
 
dBZ
 
dB(Z) – energy of reflectivity (weather radar), related to the amount of transmitted power returned to the radar receiver; the reference level for Z is 1 mm6 m−3. Values above 15–20 dBZ usually indicate falling precipitation.[23]
 
dBsm
 
dBsm – decibel measure of the radar cross section (RCS) of a target relative one square meter. The power reflected by the target is proportional to its RCS. "Stealth" aircraft and insects have negative RCS measured in dBsm, large flat plates or non-stealthy aircraft have positive values.[24]
 
Radio power, energy, and field strength
 
dBc
 
dBc – relative to carrier—in telecommunications, this indicates the relative levels of noise or sideband peak power, compared with the carrier power.
 
Compare dBC, used in acoustics.
 
dBJ
 
dB(J) – energy relative to 1 joule. 1 joule = 1 watt per hertz, so power spectral density can be expressed in dBJ.
 
dBm
 
dB(mW) – power relative to 1 milliwatt. When used in audio work the milliwatt is referenced to a 600 ohm load, with the resultant voltage being 0.775 volts. When used in the 2-way radio field, the dB is referenced to a 50 ohm load, with the resultant voltage being 0.224 volts. There are times when spec sheets may show the voltage & power level e.g. −120 dBm = 0.224 microvolts.
 
dBμV/m or dBuV/m
 
dB(μV/m) – electric field strength relative to 1 microvolt per meter. Often used to specify the signal strength from a television broadcast at a receiving site (the signal measured at the antenna output will be in dBμV).
 
dBf
 
dB(fW) – power relative to 1 femtowatt.
 
dBW
 
dB(W) – power relative to 1 watt.
 
dBk
 
dB(kW) – power relative to 1 kilowatt.
 
Antenna measurements
 
dBi
 
dB (isotropic) – the forward gain of an antenna compared with the hypothetical isotropic antenna, which uniformly distributes energy in all directions. Linear polarization of the EM field is assumed unless noted otherwise.
 
dBd
 
dB(dipole) – the forward gain of an antenna compared with a half-wave dipole antenna. 0 dBd = 2.15 dBi
 
dBiC
 
dB(isotropic circular) – the forward gain of an antenna compared to a circularly polarized isotropic antenna. There is no fixed conversion rule between dBiC and dBi, as it depends on the receiving antenna and the field polarization.
 
dBq
 
dB(quarterwave) – the forward gain of an antenna compared to a quarter wavelength whip. Rarely used, except in some marketing material. 0 dBq = −0.85 dBi
 
Other measurements
 
dB-Hz
 
dB(hertz) – bandwidth relative to 1 Hz. E.g., 20 dB-Hz corresponds to a bandwidth of 100 Hz. Commonly used in link budget calculations. Also used in carrier-to-noise-density ratio (not to be confused with carrier-to-noise ratio, in dB).
 
dBov or dBO
 
dB(overload) – the amplitude of a signal (usually audio) compared with the maximum which a device can handle before clipping occurs. Similar to dBFS, but also applicable to analog systems.
 
dBr
 
dB(relative) – simply a relative difference from something else, which is made apparent in context. The difference of a filter's response to nominal levels, for instance.
 
dBrn
 
dB above reference noise. See also dBrnC.
See also
 
• Apparent magnitude
• Cent in music
• dB drag racing
• Equal-loudness contour
• Noise (environmental)
• Phon
• Richter magnitude scale
• Signal noise
• Weighting filter—discussion of dBA
[edit] References
1. ^ IEEE Standard 100 Dictionary of IEEE Standards Terms, Seventh Edition, The Institute of Electrical and Electronics Engineering, New York, 2000; ISBN 0-7381-2601-2; page 288
2. ^ a b c Analog Devices : Virtual Design Center : Interactive Design Tools : Utilities : VRMS / dBm / dBu / dBV calculator
3. ^ Sound system engineering, p. 35, Carolyn Davis, 1997
4. ^ "Transmission Circuits for Telephonic Communication", Bell Labs, 1925
5. ^ bel. (1992). American Heritage Dictionary 3rd ed. Houghton Mifflin.
6. ^ 100 Years of Telephone Switching, p. 276, Robert J. Chapuis, Amos E. Joel, 2003
7. ^ Consultative Committee for Units, Meeting minutes, Section 3
8. ^ "Letter symbols to be used in electrical technology – Part 3: Logarithmic and related quantities, and their units", IEC 60027-3 Ed. 3.0, International Electrotechnical Commission, 19th July 2002.
9. ^ A. Thompson and B. N. Taylor, "Comments on Some Quantities and Their Units", The NIST Guide for the use of the International System of Units, National Institute of Standards and Technology, May 1996.
10. ^ "International Standard CEI-IEC 27-3 Letter symbols to be used in electrical technology Part 3: Logarithmic quantities and units". International Electrotechnical Commission.
11. ^ "Electronic Engineer's Handbook" by Donald G. Fink, Editor-in-Chief ISBN 0-07-020980-4 Published by McGraw Hill, page 19-3
12. ^ National Institute on Deafness and Other Communications Disorders, Noise-Induced Hearing Loss (National Institutes of Health, 2008).
13. ^ Thompson, Robert Bruce; Thompson, Barbara Fritchman (2004). Building the Perfect PC. O'Reilly Media. p. 14. ISBN 0596006632. http://books.google.com/books?id=sg4O8HzNbZIC&pg=PA14.
14. ^ Stephen J. Sangwine and Robin E. N. Horne (1998). The Colour Image Processing Handbook. Springer. p. 127–130. ISBN 9780412806209. http://books.google.com/?id=oEsZiCt5VOAC&pg=PA127&dq=image++db+20-log+video+voltage.
15. ^ Junichi Nakamura (2006). "Basics of Image Sensors". In Junichi Nakamura. Image sensors and signal processing for digital still cameras. CRC Press. p. 79–83. ISBN 9780849335457. http://books.google.com/books?id=UY6QzgzgieYC&pg=PA79.
16. ^ Thompson, A. and Taylor, B. N. Guide for the Use of the International System of Units (SI) 2008 Edition, 2nd printing (November 2008), SP811 PDF
17. ^ What is the difference between dBv, dBu, dBV, dBm, dB SPL, and plain old dB? Why not just use regular voltage and power measurements? – rec.audio.pro Audio Professional FAQ
18. ^ http://www.deltamedia.com/resource/db_or_not_db.html
19. ^ The IEEE Standard Dictionary of Electrical and Electronics terms (6th ed.). IEEE. 1996 [1941]. ISBN 1-55937-833-6.
20. ^ Jay Rose (2002). Audio postproduction for digital video. Focal Press,. p. 25. ISBN 9781578201167. http://books.google.com/?id=sUcRegHAXdkC&pg=PA25&dq=db+almost-always-referring.
21. ^ Morfey, C. L. (2001). Dictionary of Acoustics. Academic Press, San Diego.
22. ^ ITU-R BS.1770
23. ^ "Radar FAQ from WSI". Archived from the original on 2008-05-18. http://web.archive.org/web/20080518035848/http://www.srh.noaa.gov/tsa/radar_faq.html. Retrieved 2008-03-18.
24. ^ "Definition at Everything2". http://everything2.com/title/dBsm. Retrieved 2008-08-06.
 
 
Thank you for reading my article. 
 
Jim Dent
February 12, 2011
 
 
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