Hidden Transmitter Hunt Formats

 

There are several different formats or styles of hidden transmitter hunting describe below.


ARDF - Amateur Radio Direction Finding - This is the official radiosport form of hunting used in national and international competitions. The competitors hunt on foot, usually in a large forested area. 2 meter and 80 meter hunts are common. More information about ARDF style hunting can be found here.


Walk in the Park - This is a less formal form of ARDF used by the QARC and others. The hunters are on foot and the hunt takes place in a park. Walk in the Park style hunts use 2 meter FM.


Automotive - In this type of hunt the hunters are in an automobile. Obviously they can cover a much greater distance than on foot hunts, in extreme cases they may cover 100 kilometers or more to find all of the transmitters.


Tour of the County - This is an automotive hunt organized by the Prince Edward and Quinte Amateur Radio Clubs. It takes place in Prince Edward County, Ontario, Canada, locally just called “The County”. More information about the Tour of the County can be found here.


QRP - In a QRP hunt the transmitter power is very low, so low that it may not be heard in many locations in the search area. The transmitter may be low power, e.g. less than 1 watt, the antenna may be low gain, e.g. a rubber duck, the location may be poor, e.g. behind a hill, or a combination of all three.


The hunters may start at any location in the hunt area and could adopt a few different strategies. For example they could start at a high spot in the search area, try to get an initial bearing then move toward the transmitter. As the hunter moves toward the fox they may go through low areas where the fox can not be heard but eventually they will come within range. Another strategy could be to traverse the search area listening for the fox.


First hunter to find the fox wins.


Collaborative or Turkey Shoot - In a cooperative hunt all of the hunters cooperate to find the fox rather than compete against each other. The fox makes very short transmissions at random intervals to make the hunt as difficult as possible. For example, I might just give their call sign on the first transmission and “Fox” on the second and so on. Rather than transmitting on a regular schedule such as every 60 seconds the first two transmissions might be 15 seconds apart and the next two 100 seconds apart. The idea is to create a situation where the hunters attempt to locate the source of random transmissions that could be inadvertent or malicious. There are many examples of such transmissions; malicious transmissions intended to disrupt normal radio activities (hence the name turkey), inadvertent transmission because of an equipment failure, power line noise, it could even be the family pet. Look here for an article about such a situation.

The hunters select one or two coordinators who acts as a net controller and “general” who deploys the troops. Each mobile hunter begins at a different location within the search area and after each transmission the hunters, at least those who heard the fox, report to the coordinator with some indication of signal strength and direction. The coordinator assembles the reports and instructs the hunters to move to a new location hopefully closer to the fox. Over time they should be able to tighten the search area until the fox is finally found.

One nice aspect of this type of hunt is, for some of the hunters at least, no special equipment is required. In fact you do not even need to leave home.

  1. The coordinator can sit at home with a base station, one or two maps of the search area, and APRS running to follow the hunters.

  2. People at home with an omnidirectional antenna can report signal strength which will provide useful information, at least at the beginning of the hunt. For example if someone in Wellington reports a stronger signal than someone at Lake on the Mountain the fox is probably in the western part of the county.

  3. People at home who have a beam can provide even better information by providing a beam heading.

Hidden Receiver - In a hidden receiver hunt the fox uses a receiver and directional antenna and the hunters use standard 2 meter mobile gear. The hunters start at random locations and periodically give a short transmission then ask the fox for a bearing and signal strength. The hunter then proceeds toward the fox, asks again for bearing and signal strength, and so on until the fox is found. The hunter with the fewest “asks” is the winner. The advantage of this type of hunt is the hunters do not need any special type of gear, an ordinary mobile unit will do.