Fox Hunt

FOX HUNT:

Transmitter Hunting, or (T-hunting, fox hunting, bunny hunting, and bunny chasing), is a popular way to combine outdoor activity with the amateur radio hobby. The "Fox" hides a hidden transmitter, and the hunters use direction-finding techniques to locate it. To a radio amateur (or “ham”), fox hunting has nothing to do with animals. It is a sport in which individuals race each other to locate a hidden radio transmitter on a known frequency. Since hams are encouraged to design and build their equipment, the typical fox hunt involves a variety of different receivers and antennas with different capabilities. Some of these can display the received signal strength from the hidden transmitter (loosely measuring distance to the transmitter), while others estimate the compass bearing.

Both of these estimates vary in accuracy and precision depending on terrain, environmental conditions, equipment quality, and the skill of the operator. Fox hunting also serves the purpose of preparing radio amateurs for emergency or disaster operations. Because disaster operations require the concerted efforts of multiple radio operators, it seems fitting to explore how the sport changes if fox hunting becomes cooperative.                                                                                   

When participants combine their estimates of distance and bearing, how much faster can they find the transmitter?

Part of the challenge of fox hunting is that measurements are taken infrequently, only once every few minutes. To win the hunt, every minute must count! In the most demanding scenario, each sensor only gets to take one measurement of the fox transmitter. Locating the fox transmitter from a collection of different sensors is a model-based data fusion problem: combining disparate local observations into a global inference. Without a model that describes how signals from the transmitter arrive at each receiver, the signal reports do not help locate the transmitter. Even with such a model, the effects of terrain, the transmitter’s antenna system, and the environment can cause substantial differences between the modelled signal and an actual received signal. Therefore, we must  remain even-handed about assumptions of the quality of the estimates and the quality of the model.

There are several types of transmitter hunts. Transmitter hunting is pursued in several different popular formats. Many transmitter hunts are organized by local radio clubs and may be conducted in conjunction with other events, such as a radio enthusiast convention or club meeting. Before each hunt, participants are informed of the frequency or frequencies on which the transmitters will be operating, and a set of boundaries that define a search area in which the transmitters will be located. Transmitter hunters use radio direction finding techniques to determine the likely direction and distance to the hidden transmitter from several different locations, and then triangulate the probable location of the transmitter. Some hunts may include limits on the amount of time allowed to find a transmitter. Although many transmitter hunts are conducted just for the fun of the activity, some more competitive hunts will recognize winners in publications and offer awards, such as medals or trophies.

Few of the most famous Fox-hunt types are:

1)Mobile transmitter hunts:

Mobile transmitter hunts are organized events where participants travel exclusively or primarily in motor vehicles. Most mobile transmitter hunts use VHF transmitters and receivers.

Some participants use radio direction finding equipment and antennas mounted on a vehicle, whereas others use antennas that are temporarily deployed in an open window or an opening in the vehicle roof that can be easily rotated by hand while the vehicle is in motion. Other participants employ handheld antennas and radios that can only be used when the vehicle is stationary. Some mobile transmitter hunts require participants to leave their vehicles and proceed on foot to reach the actual location of the radio transmitter. The winner of a mobile transmitter hunt can be either the first vehicle to arrive at the hidden transmitter, or the vehicle that travels the shortest overall distance to locate the hidden transmitter. Mobile transmitter hunts are more popular in North America than in other parts of the world.

2)Pedestrian transmitter hunts:

A regulated sport form of transmitter hunting by runners on foot is called Amateur Radio Direction Finding, known worldwide by its acronym, ARDF. It is an amateur sport that combines the skills of orienteering and radio direction finding. ARDF is a timed race in which individual competitors use a topographic map and a magnetic compass to navigate through a diverse, wooded terrain while searching for hidden radio transmitters. ARDF is the most popular form of transmitter hunting outside North America.

3)Fixed location transmitter hunts:

Some transmitter hunts feature a "mail-in" competition, in which teams in fixed locations work together to locate hidden transmitters, then secretly give the coordinates to the organizers without actually traveling to the transmitter location. The team which provides the closest coordinates wins, thus a team which believes that the transmitter is in the northwest parking lot at 2nd and Elm (if it is there) will beat a team which says that the location is 2nd and Elm. This type of hunt enables participation by contestants who are unable to travel, such as shut-ins, school groups, etc., and requires a greater level of skill and coordination.

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