Projects: The FoxBox

The FoxBox

This article describes a Grand Rapids version of the popular FoxBox remote controlled fox hunting transceiver.  Ideal for hiding out-of-sight for extended periods of time, this unit features a 2-meter hand-held transceiver, a Byonics PicCom Hidden Transmitter Controller and two dry cell batteries. The military surplus ammunition case makes an ideal secure environment for the equipment.

We would like to thank Paul Gibson, N1TUP and other members on the Connecticut Fox Hunter Yahoo Group for providing pictures and other technical information that helped us construct our FoxBox.
http://groups.yahoo.com/group/CTFoxHunter/
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The FoxBox during initial deployment in Whistlestop Park in Byron Center, Michigan. The box was secured to the adjacent tree with a steel chain and lock. Camouflage, consisting of leaves and sticks finished the job.

How does it work?

The FoxBox uses a hand-held transceiver (HT), a microcontroller module, a pair of dry cell batteries and a "rubber ducky" antenna as shown in the following block diagram. The HT receives DTMF tones from a remote operator and sends them on to the microcontroller through it's headphone cable. These tones are used to program the microcontroller or to perform basic start/stop commands. In turn, the microcontroller sends a transmit/receive command and audio tones to the HT through the HT microphone cable. These tones include random sequence tones for output audio and morse code for transmitter identification.

FoxBox Block Diagram

 
The Grand Rapids FoxBox uses the Yaesu FT-250R 2-meter HT as the transceiver. The FT-250R is a low cost, small footprint unit with several features designed to minimize battery drain while in receive mode. In addition, and most important, is it's ability to run on an external 6 VDC to 16 VDC battery. (Not all HTs will handle the higher voltages of a standard gel-cell battery.)  We set the HT to 145.530 Mhz (our local fox hunting frequency), set the squelch and volume as normal and plugged-in the purchased cables for power, headphones and microphone.  The output power is set to 2 watts.  We call this "set it and forget it."  The external "rubber ducky" antenna is connected to a BNC chassis feed-through connector on the cover of the fox box and connected to the HT with a short coax cable. 

The microcontroller is the Byonics PicCom Hidden Transmitter Controller.  (See side panel)  This very small unit consists of a microcontroller chip and a DTMF decoder chip along with a few miscellaneous components.  It comes completely assembled and tested (or in kit form).  If you choose to use this controller, be sure to buy the optional cables.  There are several cables available for different HT and mobile units. They are well worth the cost.  You program the controller with DTMF tones from a remote transceiver.  It comes preset to a default configuration, but you will want to modify the setup to at least give your call letters for identification.  The controller has plenty of setup functions to fit your needs as your expectations grow.  The instruction manual is well written and very helpful.  (See side panel for download.)

The batteries are a pair of 12 volt, 7.5 amp/hour sealed lead acid types which are wired in parallel. The power wiring is the only custom wiring in the FoxBox. The batteries are wired directly to a DPDT toggle switch.  One position of the switch connects the batteries to the transceiver and controller for normal operation.  The other switch position connects the batteries to a pair of banana terminals (not shown) for recharging the batteries.  Each battery weighs about 5 pounds.  The Fox Box will run on these batteries for about 2 weeks in a query/response mode. (Depending on transmitter use.) In a repeating cycle mode, the batteries will last for several hours -- plenty long enough for a standard afternoon team hunt.  (Note:  charging is fused at 1 amp and normal operation is fused at 5 amps.)

For the external antenna, the FoxBox has a BNC thru chassis UG-492 coupler (Female on both ends) mounted on the lid of the ammo box.  A short coax cable runs from the coupler to the transceiver.  A "rubber ducky" antenna mounts on the outside of the box. Normal range with this antenna and 2 watts of power is about 3 to 4 miles.

The completed FoxBox sitting on the bench being programmed.  Locals continue to discuss the wording of notices to be attached to the outside of the box alerting police to our honorable intentions.

Total Weight: 19.5 pounds.
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An eye-bolt is attached to the front on the box, through the closing latch, for security.
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Note the external antenna mounting connection where the "rubber ducky" currently sits.  Other various antennas can be routed up a tree for greater range.
 
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Note the Byonics PicCon hidden transmitter hunting controller in the green plastic box above the transceiver. Click the pictures to see a larger view.  (Banana connectors for charging the batteries have been added since these pictures were taken.)

Click pictures to enlarge.
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