Chapter 1
Coming to Terms with Terms
Introduction | Terms | On-foot VHF Hunt Equipment | Mobile VHF Hunt Equipment | Strong Signal Tactics | References

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Like other hobbies, transmitter hunting has its own nomenclature. The following definitions and explanations are provided to help acquaint the reader with a few of the more common transmitter hunting terms. These definitions are not intended to cover every context in which the terms might be used, but simply to describe them in the context of transmitter hunting.

In this section I have tried to keep the use of technical jargon to a minimum. However, in the interest of brevity, I have resorted to using some technical terms. If you are not technically inclined, don't feel daunted by any jargon you might encounter here. Remember: you don't need to understand the theory in order to successfully hunt down hidden transmitters. But, once you've spent some time hunting transmitters, you may find that you've attained a practical understanding of radio that makes the theory easier to grasp. 

Antennas

An antenna is a metallic device that converts radio waves striking its surface into electrical signals that can be fed into a receiver. The cable (or wire) that connects an antenna to a receiver is known as a feedline, because it feeds the signal into the receiver. The size, shape, height, design, and orientation of an antenna determine its operating characteristics, such as directionality and polarization. Fortunately for most television viewers, one doesn't need to know anything about antenna theory in order to successfully use an antenna. But for those interested in the topic, references [1], [2] and [3] are a good place to start learning about antennas.

Clearly, all transmitter hunting tools require an antenna of some sort. Many, but not all, utilize a member of a family of antennas called beam antennas (or beams). All members of the beam family share one trait in common: they receive best in one direction, and less well in all others. This makes using a beam antenna very simple: just wave the antenna around until you find the direction that an attached receiver indicates the strongest signal. Barring complicating factors, such as signal reflections, the transmitter will be found in that direction. 

Beam family members include yagis, quads, log-periodic dipole arrays, HB9CV antennas, helical antennas, corner reflectors, horn antennas, parabolic dishes, and many others. Not all beams are suitable for on-foot, or mobile, transmitter hunting. Some of the more practical and effective beams for transmitter hunting are described on this web site.

Attenuators

An attenuator diminishes (attenuates) the strength of the received signal. Why use an attenuator? As you near a transmitter, its signal strength will increase until it eventually maxes-out your receiver's S-meter, and provides your receiver with a strong static-free signal. Placing an attenuator in the feedline between your antenna and receiver will knock the signal strength down sufficiently so that your S-meter, or the noise on the received signal, can be used to observe signal strength variations as you proceed with the hunt.

Attenuators can be divided into two broad categories:

Active Attenuators
Active attenuators make use of active components and thus require a source of power (e.g., a battery) in order to function. The offset attenuator is an example of an active attenuator. 

Passive Attenuators
Passive attenuators contain no active components, but inherently impose an absorptive or reflective loss directly to any signal passing through them. The resistor network attenuator (or resistor step attenuator), and the waveguide attenuator (see reference [3]), are examples of passive attenuators. 

See Tactics for Strong Signals for more information on attenuators.

Fox

The Fox is the individual responsible for hiding the transmitters. Because the Fox is in control of the transmitters, he (or she) is the only person who may be required to possess a radio operator's license.

Hound

The Hounds are the individuals who pursue the transmitters hidden by the Fox. Because the Hounds do not transmit (they only receive) they are not required to possess a radio operator's license.

Polarization

Radio waves leaving an antenna have a property called polarization. Most of the antennas used in transmitter hunting emit radio waves that are linearly polarized. Antennas that emit linearly polarized radio waves will receive linearly polarized radio waves most efficiently when both the transmitting and receiving antennas are oriented the same way. Simply put, it is usually to your advantage to orient your receiving antenna so that it matches the orientation of the transmitting antenna. For example: if the transmitting antenna is oriented so that the transmitted signal is horizontally polarized, then you will usually get more reliable bearings if your receiving antenna is also oriented for horizontally polarized signals. 

If you are not told how the transmitting antenna is oriented, you may have to experiment to discover how to orient your receiving antenna for the most consistent and unambiguous bearing measurements.

If you are not sure how to orient your receiving antenna for horizontally or vertically polarized radio waves, then I would recommend spending a few moments researching the topic in reference [1], [2] or [3], or asking a friendly fellow transmitter hunter.

Receivers

A radio receiver converts the electrical signals, arriving from the antenna, into sound waves and meter movements that you can hear and see. Many transmitter hunting tools require an external radio receiver to make them work. Others come with their own built-in receiver.

For most on-foot hunting with a quad or yagi antenna, you won't need a fancy receiver. Any handheld radio capable of receiving FM signals on the 2-meter amateur band, and providing an indication of signal strength, will be perfectly adequate. In fact, you can use the noise (or quieting) you hear coming from the receiver as an audible indication of signal strength. Which means virtually any handheld programmable scanner capable of covering 144 MHz to 148 MHz should work just fine.

Rules

Because of the wide range of crafty transmitter hiding possibilities available to the Fox, and the need to keep the level of difficulty commensurate with a hunt's time limits, strict rules are often imposed on transmitter placement and operation. Transmitter hunt rules bear consideration because they can have an impact on the hunting equipment you choose. 

Within the United States, transmitter hunt rules range from minimal to elaborate. Rules here generally are derived from tradition (or from imagination), and are imposed at the discretion (or whim) of the individual hunt organizers. As a result, there are no common rules by which inter-regional competitions can be held. Nevertheless, the freewheeling nature of U.S. transmitter hunts makes for a diverse and dynamic mix of hunters, hunt equipment, and hunt methods. It is a good idea to consult with local hunters and hunt organizers to help you determine the appropriate choice of transmitter hunting equipment.

Internationally, the situation is quite different. The International Amateur Radio Union is recognized as the body with the authority to establish the rules by which transmitter hunts are conducted, and by which championship competitions are sanctioned. The sport, known as Amateur Radio Direction Finding (ARDF), is defined by explicit rules, and is conducted in a similar manner worldwide. Regional and world championships are held on a regular basis. The rules give hunters a great deal a latitude in their choice of hunt equipment. However, because ARDF hunts are entirely on foot, size and weight are of paramount importance when choosing hunting equipment. 

Transmitters

The transmitter is the device that generates a signal for all the hunters to seek. Most transmitters are capable of operating over a range of frequencies (called a band), and can impart information on the emitted signal (a process called modulation) using one or more techniques. In the United States, most recreational transmitter hunts are conducted using transmitters that operate on the 2-meter band (144 MHz to 148 MHz), and use frequency modulation (FM). In much of the rest of the world, hunts are likely to use transmitters that operate within the  2-meter band (144 MHz to 146 MHz) or the 80-meter band (3.5 MHz to 3.7 MHz), and use either amplitude modulation (AM) or modulation imparted by turning the signal off-and-on in the pattern of the International Morse code (also called CW modulation). The output power of most transmitters used for recreational transmitter hunts is in the range of a few milliwatts (0.001 Watts) to 5 Watts.

Surprisingly, finding the transmitter is not the objective of most transmitter hunts. What the hunters are actually searching for is the antenna connected to a transmitter. The reason for this is that the majority of a transmitter's signal radiates from the antenna to which it is attached, not from the transmitter itself. This technicality is somewhat academic since a transmitter and its antenna are usually located close together. But the point is worth noting because sometimes the transmitting antenna may be attached to the transmitter by a lengthy feedline, which can lead to confusion. Having identified the antenna, overenthusiastic hunters have been known to yank the feedline completely out of its connector, in an attempt to identify the ultimate source of the signal! 

A single transmitter hunt might involve one or multiple transmitters. Transmitters might be on one frequency, multiple frequencies, or even on different bands. They might be on the air continuously, periodically, or at random intervals. Transmitters might be carefully timed so as to prevent more than one transmitter from being on the air at the same time. Or, they could be timed so as to ensure that two or more transmitters are always on the air at the same time. Transmitters, and their antennas, may be clearly identified with a brightly colored marker, or they could be carefully camouflaged or disguised. Transmitters may be stationary, or attached to a moving automobile, boat, or aircraft. A transmitter's power level, modulation characteristics, and its antenna's orientation might also vary during the course of a hunt. Because of all the ways that transmitters can be made difficult to find, a set of rules is usually imposed on the Fox

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Introduction | Terms | On-foot VHF Hunt Equipment | Mobile VHF Hunt Equipment | Strong Signal Tactics | References

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