Fox Hunting With Software-Defined Radio

December 26, 2020 by 7 Comments

Fox hunting, or direction finding, is a favorite pastime in the ham radio community where radio operators attempt to triangulate the position of a radio transmission. While it may have required a large amount of expensive equipment in the past, like most ham radio operations the advent of software-defined radio (SDR) has helped revolutionize this aspect of the hobby as well. [Aaron] shows us how to make use of SDR for direction finding using his custom SDR-based Linux distribution called DragonOS.

We have mentioned DragonOS before, but every iteration seems to add new features. This time it includes implementation of a software package called DF-Aggregator. The software (from [ckoval7]), along with the rest of DragonOS, is loaded onto a set of (typically at least three) networked Raspberry Pis. The networked computers can communicate information about the radio waves they receive, and make direction finding another capable feature found in this distribution.

[Aaron] has a few videos showing the process of setting this up and using it, and all of the software is available for attempting something like this on your own. While the future of ham radio as a hobby does remain in doubt, projects like this which bring classic ham activities to the SDR realm really go a long way to reviving it.

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Fox Hunting With A Raspberry Pi

November 6, 2014 by 11 Comments

No, not a real fox! [KM4EFP] is a ham radio operator with a passion for fox hunting, which is an event where several radio operators attempt to find a broadcasting beacon (a “fox”) using radio direction finding techniques. [KM4EFP] has just built his own portable fox using a Raspberry Pi in a very well-built enclosure.

Since the fox could be outside for a while, the project was housed in a reasonably weatherproof ammunition case. A mount for an antenna was attached to the side, and it is hooked up to a GPIO pin on the Raspberry Pi. The entire device is powered by a 6000 mAh battery pack which allows the fox to broadcast long enough to be found.

The software running on the Raspberry Pi is very similar to the Pi FM transmitter program but it is specially made for ham radio broadcasting instead. Almost no extra hardware is needed to get the Pi broadcasting radio, as these software packages can drive the antenna directly from the GPIO pin. This is a great twist on the standard FM transmitter that ham radio enthusiasts everywhere can use to start finding those wily foxes!

Turning An Easter Egg Hunt Into A Fox Hunt

April 4, 2013 by 4 Comments

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We’ve seen [Todd Harrison]’s work a few times before, but he’s never involved his son so throughly before. This past Easter, he thought it would be a good idea for his son and a few of his friends to take part in an easter egg hunt. Being the ham he is, he decided to turn an easter egg hunt into an adventure in radio direction finding, or as amateur radio operators call it, a fox hunt.

[Todd] put together a great tutorial on building a yagi – a simple directional antenna – out of a couple of pieces of PVC pipe and a few aluminum and brass rods. With this and a handheld ham set, [Todd] hid a fox along with a stuffed easter bunny and a basket of candy near a local park. Operating under the guidance of his dad, [Todd]’s son and his friends were eventually able to find the fox. Leaving candy out in the Arizona sun probably wasn’t [Todd]’s best idea – the fox, and candy, were covered in ants when they were found – but it was a great introduction to amateur radio.

Wearable Foxhunt Transmitter For Conventions

August 31, 2017 by 13 Comments

Amateur radio operator [KE4FOX] wanted to build his own 2M fox hunt transmitter for use at conventions. It would be contained in a 1020 Pelican micro case and attached to a person who would walk around transmitting a signal, leaving the hams to track down the fox. The project uses a DRA818 VHF/UHF transceiver plugged into a low-pass filter combined with a hardware DTMF decoder, all controlled by an ATmega328P and powered by a 11.2 mAh battery.

[KE4FOX] also etched his own PCB, using the PCB toner transfer method, folding a sheet of transfer paper around the board to align both layers. Then he etched the board using cupric chloride. When assembling the board he realized he had made a terrible error, assuming the transceiver module’s pins went in the top layer when in fact they should have gone in the bottom layer. He solved this by soldering in the module in upside down.

He dropped the project into the 1020 and installed an SMA antenna. After he assembled the project he found out that the level shifter he used on the Arduino’s 5 V data didn’t work as expected and it was stuck at a single frequency. Something to work on for V2!

We publish a large number of amateur radio posts here on Hackaday, including fox hunting with Raspberry Pi and how to make a TDOA directional antenna.

[thanks, that Kat!]

FRS Foxhunting For Model Rockets

April 5, 2008 by 10 Comments


Since we had a FRS radio hackit a while back, [Weirdguy] sent this in. [Scott] gutted a frs radio and added it to his rocket chassis. It’s powered on for the flight, and he can listen to the rockets progress. To locate the rocket once it’s on the ground, he built a 462Mhz Yagi antenna to use with a Radio Shack hand held scanner. This is old hat for most Ham Radio guys – they do ‘Fox Hunts‘ for hidden transmitters just for fun.

Be Vewy Vewy Quiet, We’re Hunting Baofengs

March 3, 2019 by 24 Comments

In the world of ham radio, a “Fox Hunt” is a game where participants are tasked with finding a hidden transmitter through direction finding. Naturally, the game is more challenging when you’re on the hunt for something small and obscure, so the ideal candidate is a small automated beacon that can be tucked away someplace inconspicuous. Of course, cheap is also preferable so you don’t go broke trying to put a game together.

As you might expect, there’s no shortage of kits and turn-key transmitters that you can buy, but [WhiskeyTangoHotel] wanted to come up with something that could be put together cheaply and easily from hardware the average ham or hacker might already have laying around. The end result is a very capable “fox” that can be built in just a few minutes at a surprisingly low cost. He cautions that you’ll need a ham license to legally use this gadget, but we imagine most people familiar with this particular pastime will already have the necessary credentials.

The heart of this build is one of the fairly capable, but perhaps more importantly, incredibly cheap Baofeng handheld radios. These little gadgets are likely familiar to the average Hackaday reader, as we discussed their dubious legal status not so long ago. At the moment they are still readily available though, so if you need a second (or third…), you might want to pull the trigger sooner rather than later.

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Hunting Rogue Access Points With The ESP8266

December 28, 2017 by 32 Comments

Cantennas outperform every consumer-grade Wi-Fi antenna I’ve had the bad luck of purchasing. Cantenna is a mashup of ‘can’ and ‘antenna’ creating the nickname for a directional waveguide antenna built from re-purposed steel cans. For anyone who has yet to build one, it makes an excellent afternoon project. Here are some build instructions and technical details. I went beyond that, and ended up catching a rogue WiFi access point in the process.

When I needed to extend the range of some ESP8266-based sensors, cantennas were right at the top of my list of things to try. It was easy enough to build one, attach it to a Wemos Mini D1 Pro, and call the job done… leaving me with plenty of time to over-engineer it, and I ended up down a bit of a rabbit hole.

The first thing I did was stop using cans. Canned goods are not only expensive in my corner of the world, but more importantly don’t lend themselves that well to making a standardized antenna in volume. I can also only eat so many beans! The latter reason alone is enough to consider an alternative design like a modular dish reflector.

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