Ideas for building your own fox

Sooner or later you will want to put together your own transmitter, so that you won't have to borrow someone else's. Here are some of the things you'll have to consider when deciding what kind of rig is best for you:

The Transmitter
The Controller
General Suggestions

The Transmitter

How much power output will be required?
Will the finals have to endure long duty-cycles?
Will only one frequency be adequate, or will you want to be able to choose other frequencies?
Does it have to be SMALL?

Some commercial transmitters that have been "field proven" include:

The HAMTRONICS 2-watt FM Exciter.
This crystal-controlled transmitter has adjustable power output, and is reliable. Available from Hamtronics, Inc., 65-D Moul Rd., Hilton NY, 14468-9535 (716)-392-9430.

The ICOM IC-2AT handi-talkie.
This older model HT can run on low power (100mw) all day long without burning up the finals, is frequency adjustable, and can still be found at hamfests at low prices ($75).

A postage-stamp sized transmitter is available from Airtek, 2306 Turquoise Circle, Chino Hills, CA 91709. This unit was described in the Homing in column: "Teeny-Weeny T's" (73 Amateur Radio Today magazine, May, 1993).

A 5-mw transmitter is available from Don Lewis KF6GQ. Very small, it uses voice ID, and has a built-in controller which cycles the signal on and off. Contact GQ Enterprize, Suite 524, 129 East Colorado Boulevard, Monrovia, CA 91016. This "T" was described in the Homing in column: "Multiple Foxes = More Fun" (73 Amateur Radio Today magazine, March, 1995, pg 64.)

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The Controller

The functions of the controller are:

Control the ON/OFF cycle of the transmitter.
Provide audio to the transmitter during the ON cycle.
Provide the required ID at least once every ten minutes.

Some questions you will want to consider:

What On/Off cycle do you want to use?
Do you want a CW- or Voice-ID?
Do you want random tones, a recorded voice, or something else to be heard during the "on" cycle?
Do you want to be able to program all the above to suit different hunt-styles?

A microprocessor-driven controller designed by Ron Seese N6MBR was described in the Homing in column: "Build the TBOX" (73 Amateur Radio Today magazine, October, 1991). Boards and parts for this unit are available from N6MBR. Several T-hunters here in Albuquerque use this controller with various transmitters, and it has been proven very reliable.

Ron's current address is:
1535 Thornhill
Westlake Village CA 91361

email address: n6mbr@chrislin.com

A Voice ID T-hunt Controller was described in the article: "The Foxbox" (73 Magazine, March 1994, pg. 42). This has been built and used by several Albuquerque T-hunters, and uses Radio Shack parts. Circuit boards are available from FAR Circuits, 18N640 Field Court, Dundee, Il 60118.

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General Suggestions

Here are some general suggestions to help you get the most use from your fox.

One, standardize all connectors. For example, use one type for power, another type for controllers, another type for mics, etc. This will prevent wrong-polarity power connections, prevent connecting the wrong components to each other, and allow you to "mix-and-match" if you have multiple transmitters, batteries, or controllers.

Even better, get all the members of your transmitter-hunting group to agree on connector "standards". That way, you can lend or borrow components with your buddies, too.

Need a waterproof container for the fox? Surplus ammo-cans, found at most surplus stores and flea markets, make good, weatherproof housings for a fox, are inexpensive, and probably do not radiate much signal themselves. This latter may be important if, say, you plan to feed an external beam-type antenna to get directivity. You don't want the box to radiate a signal too, and give a direct signal to the hiding spot, defeating the use of the beam. While on this topic, give some consideration to your feedline. Good quality, double-shielded coaxial cable may also help reduce this problem. Type RG-223 is popular for this reason. Some hunters have been known to place a stack of toroids around the coax, to reduce the chances that the outer braid of the coax may become an antenna.

Back to the ammo-can, some can be padlocked, which may be useful if you won't be able to watch it at all times. By mounting a U-bolt through the can, you can also chain it to a tree or other permanent object, for additional security, if necessary.

If you are going to leave a fox unattended, be sure to put a large label on it, to tell anyone who might spot it what it is. These days, with idiots setting off bombs everywhere, this might keep you from having to explain to the law what your strange little box is all about. It might also keep vandals from damaging it (hah). An example label might read:

      THIS IS AN FCC-LICENSED AMATEUR RADIO TRANSMITTER
      OPERATING FREQUENCY: _______________________
      CALL SIGN: _______________________

      CONTACT: _________________________ PHONE: ___________
      
      THE CODE WORD FOR TRANSMITTER-HUNTERS FINDING THIS 
      TRANSMITTER IS: ____________________
      
      THE CALL-IN FREQUENCY IS: ______________________

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