December 12, 2020

Evaluating Radio Fox Hunt Alternatives for a Scout Troop

During the Summer of 2020, I taught the Radio Merit Badge for a troop of enthusiastic Scouts.  The scouts had a great time setting up a wilderness radio station and operating on HF, VHF, and UHF.  Part of the curriculum included discussing various radio related activities that amateur radio operators participate in.  The scouts were really excited to learn about amateur radio fox hunting (also known as amateur radio direction finding).  The scouts asked if they could organize a radio fox hunt for the troop sometime.  The answer was of course was an equally enthusiastic, "Yes!"  (I only needed to figure out how to do it first).

Radio fox hunting (also called amateur radio direction finding or radio orienteering) is a challenging amateur radio sport that combines radio direction finding with orienteering map and compass skills.  Radio fox hunting is a timed race in which competitors use a topographic map, a magnetic compass, and radio direction finding apparatus to navigate through diverse wooded terrain while searching for hidden radio transmitters.

The objective of this hunt is to have fun using leadership skills in an inter-patrol competition while also developing radio direction-finding skills.  Teamwork, skills, and speed are all advantages.

When I started working on an approach for a radio fox hunt I began with the end in mind by drafting a set of requirements:
  • Waterproof - We don't get much rain here in Northern California.  However, we can experience huge downpours during the rainy season that starts with the onset of Winter.  The  electronics need to stay dry rain or shine.
  • Sufficient Battery - The transmitter equipment for the hunt will transmit on a 50% duty cycle for the duration of a hunt and demonstration / practice prior to the hunt.  The total operating duration will likely be between 120 minutes and 150 minutes.  The transceiver will likely be run on low power.  Battery storage that will support 4 hours would probably be good enough.
  • Stealthy - The fox transmitter will need to be hidden from view from both hunters and passers by.  The transmitter profile needs to be discreet and easily hidden behind weeds or inside a bush.  Camouflage or dark color would be appropriate.
  • Labelled -  The transmitter needs to be labelled to inform a finder of its purpose in the event of accident discovery.  The label will also help a radio fox "hound" quickly confirm she has found the transmitter during a hunt.
  • Secure - Provide the ability to secure the radio fox transmitter to a tree with a bicycle cable lock to deter theft.
  • Auto ID - The fox transmitter needs to be able to identify the call sign every 10-minutes per FCC rules.
  • Intermittent Transmission - The fox transmitter needs to alternate between sending a signal for the hounds to locate and then going idle with no transmitted signal.  A 50% duty cycle of 15 seconds on and then 15 seconds off would be about right.
  • Lightweight - The fox transmitter device needs to be relatively lightweight to promote easy portability as part of backpacking outing or hike.  This limits the weight to a couple of pounds maximum.
Armed with requirements, I researched various options for setting up a radio fox transmitter.  I identified three basic alternatives:
  1. Transceiver + radio CW beacon - Use a 2m handy-talkie as a transmitter interfaced with a CW beacon controller.
  2. Transceiver + radio fox controller - Use a 2m handy0talkie as a transmitter interfaced with a fox controller.
  3. Dedicated integrated radio fox transmitter - These are special purpose radios with a built-in radio fox controller.

Option 1: Transceiver + Radio CW Beacon

  • Lowest cost since existing equipment could be repurposed
  • Easy to setup
  • Flexible frequency and power (determined by the transceiver)
  • CW beacon could be paired with different radios
  • Not a commonly adopted approach for radio fox hunting
  • A CW signal could be more challenging for new fox hunters to locate with rudimentary techniques such as body fading.
  • Requires an additional battery pack
  • Requires a waterproof container to deploy

Option 2: Transceiver + Radio Fox Controller

  • Proven effectiveness in radio fox hunting
  • Likely easier for new radio fox hunters to locate with rudimentary techniques such as body fading
  • Flexible frequency and power (determined by the transceiver)
  • Fox controller could be paired with different radios
  • Additional expense in purchasing a radio fox controller
  • Requires an additional battery pack
  • Requires a waterproof container to deploy

Option 3: Dedicated Integrated Radio Fox Transmitter

  • Proven effectiveness in radio fox hunting
  • Smallest physical size and lightest weight - easiest to hide - stealthy
  • No additional battery pack required
  • No additional waterproof container required
  • Additional expense in purchase a integrate radio fox transmitter
  • Highest cost approach
  • Low power with no options
  • Fixed frequency / less flexible in terms of frequency

After considering the pros and cons of the three options, I decided to start with Option 1 by pairing a vintage 1990's 2m Kenwood HT with an existing CW-keyer that I had available in the shack.  This option would provide a zero-cost opportunity to experiment with using a CW beacon for radio fox hunting.  In my next post in this series, I will share how I configured my first fox transmitter and what I learned in the process.

Good DX and 73, NJ2X

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