Signal Safari Information

Quick writeup of resources used in preparation for the Signal Safari workshop at the IEEE Student Activities Conference 2026

Slides used for the first 20 minutes of the workshop

Background on the workshop name

In the past, these activities have been referred to as a "fox hunt" and most resources online at time of writing use that term. The real practice of hunting foxes is pretty cruel and brutal, so our goal is to rename the activity to reflect the activity of making observations about the RF environment while outdoors. Hence: a signal safari!

Building the antenna

• Two-page sheet of instructions with Dr. Alan Johnston's modifications in red
• Workshop participants: see your email for a link to Dr. Johnston's 15 minute video background on the activity. (It's not my place to a post a public link to his video, sorry!)
• Follow his SDR++ installation instructions

Any RTL-SDR should be fine. Lots and lots of different types are available! Also, SDR++ is just one of many pieces of software out there that will work with an RTL-SDR.

Building the transmitter

• To get morse code as an audio signal that looks like voice a Baofeng can transmit, I used Arduino code lightly modified from W1RCP's code (version 2). The wiring diagram is great. Here's a video with a walkthrough of the code albeit version 1. The exact capacitor value doesn't matter much. I cut apart the earpiece/mic accessory included with the Baofeng radios to make the interface. The wires inside are not easy to work with so I recommend prying open the mic box and desoldering the leads you need so there is already a small amount of wire without insulation ready to solder to.
• Configure the Baofeng to use Vox, level 2
• Power the Arduino off of a USB power bank. Most USB power banks can be configured to supply power regardless of whether there is a load connected -- you must do this because many Arduinos don't draw enough current for the power bank to notice. This means the morse code generator will power down seconds after you power it on.
• Tape it all down in a box because it will rattle around and disconnect something otherwise.
• Another resource I consulted uses a resistor in series with the signal pin. That's probably fine but I didn't test it. The wiring diagram shows a 4-pole audio connector but a 3-pole works fine as illustrated in W1RCP's article at the top of this list.
• This video was pretty clever -- use an audio recording and an adapter cable to "play" the looping message from an old phone. I didn't test this one but it seems nice for the future.

Choosing transmit frequencies

• Consult the ARRL band plan
• Check Repeaterbook and consult with your local amateur radio club to identify repeaters to avoid
• Set the Baofeng to narrow transmission bandwidth
• Be sure the the transmitted message and wait time leave you end up with a transmitter duty cycle of around 20-30%. Advise participants to set timers to the off time when outside so they know when to actively listen for transmissions.