Fox Hunts

Put your directional finding skills to use and join us every weekend for our RWK Foxhunt! Foxes are placed somewhere within the city limits of Richardson every Saturday morning. Fox#1 chirps on 144.500MHz every couple of minutes. There also is usually another fox (“Wheatley”) on a UHF frequency (433.250MHz).

The foxes are usually active from Saturday morning until Sunday afternoon (or until the battery gives out or weather gets bad). Your goal is to find the fox and log your entry. Use your best radiolocation techniques (see below) to locate the fox. Once you find the fox, just use your smart phone and “shoot” the QR code on the front of the Fox with your camera to go to the online fox hunt log. If you can’t get the QR code to work, type in the coded URL printed close to the QR code from any phone or computer. Each Fox has its own online log (see right) so you can see who has found the fox that weekend.

Please join the K5RWK groups.io discussion group for up to the minute news about Fox deployments! One of the best ways to learn foxhunting is to ride along with an experienced hunter – let us know by posting a message on the groups.io list if you’re looking for a “ride along” opportunity.

Happy hunting!

What Is Foxhunting?

Foxhunting (hidden transmitter hunting) participants attempt to find a hidden transmitter (the “fox”), using handheld or mobile directional antennas within a designated area. As a minimum, you will need a mobile or portable 2M radio and usually a directional antenna, although some hunters use multiple radios and specialized DF (direction finding) antennas. You can work alone or in teams to find the fox.

While foxhunting is fun on its own, it’s actually good practice for hams to be able to find malicious or unintended interference from other radio sources. It’s important to have a good team of trained “hunters” to nail down interference sources, and foxhunting is great training.

How To Get Started

As a minimum, all you need is a portable VHF/UHF radio (HT) or mobile radio with a car-mounted antenna. A radio that has a good S-meter (signal strength) will be helpful. You’ll probably also want a directional antenna (yagis and loops are popular options – see below for a cheap build-it-yourself tape measure yagi). Then just listen on the published frequency after the hunt is announced. If you hear the fox, use a combination of signal strength and a directional antenna to try to determine which direction it’s in relative to where you are. After a few receptions, you should be able to close in on the general location. For the “end game” (finding the actual fox when you’re very close), you may need some additional tools or techniques – see the tips below.

Foxhunting Tips

• Know your radio – get a feel for how your radio sounds for close, strong and weak signals. This will give you an initial indication of how far you are from the fox.
• Use a directional antenna – You should have a portable “DF” antenna that you can point while listening to the fox. You should be able to narrow down the general direction of the fox from your location.
• Triangulate – Take readings from multiple locations and see if your readings converge to a smaller area. This will lead you to the next location closer to the fox.
• Weak is Strong – While most small yagi antennas have a fairly wide (30-40 degree) main lobe, sometimes the nulls off the back can be much sharper. Search for the null and the fox will be in the opposite direction.
• Attenuate – When you get close to the fox, it will be harder to listen for signal changes from your antenna. Use an attenuator to drop the signal to a lower level. Your body also makes an excellent attenuator at VHF/UHF – by holding your HT close to your chest and rotating you can sometimes find a null.
• Beware of reflections – Just like light off a mirror, RF can reflect off of large, flat surfaces. These reflections can seem like valid sources but they will only make you mad (hint: sometimes the foxmasters do this on purpose!).
• Shift Frequencies – Especially on FM, a shift of 5kHz or 10kHz up or down from the fox frequency, will weaken the signal enough to get a better direction reading.
• Use Harmonics – No transmitter is perfect, and some are outright dirty when you get close. Listen for the third harmonic of the signal (third harmonic of 144.5MHz is 433.5MHz) – if you hear the third harmonic, you are very close!

Helpful Presentations and Materials

• Getting Started With Foxhunting (KD4C Presentation to MARS)
• Build an inexpensive Tape-Measure Yagi antenna for foxhunting! (offsite link)
• Build a 70cm tape-measure antenna (to hunt Wheatley)
• Amateur Radio Direction Finding Presentation by Andrew Koenig, KE5GDB
• A park foxhunt video using the Tape-Measure Yagi (YouTube)
• Jay KE5FMS shows how he uses just a HT to hunt the fox.

Meet The RWK Foxes!

FOX#1 – He was the first RWK Fox, built by KE5GDB and modified by KD4C. He is big and powerful and is always found on 144.500MHz and features the smooth, soothing ticks of WWV (and occasionally some SSTV – download an SSTV app to your phone and you can see what the fox says!). Fox#1 may be tracked here.

WHEATLEY – So named because he features Wheatley from Portal2 (the voice of Stephen Merchant), he was built by K5CG and has become a dependable and wily Fox. He can be found on 433.250MHz and mostly is in Richardson, but occasionally ventures north. Wheatley may be tracked here.

RWK Fox Placement Rules

The RWK Foxes will usually be placed based on the following rules:

1. Foxes will usually only be on Commercial or Public property. A Fox will rarely be on residential property (unless he has permission from the owner). Foxes are also pretty good about respecting “no trespassing” signs.
2. Foxes should be visible from the car and will be “vehicle accessible” – you shouldn’t have to walk more than 25 feet from your car to log the fox. There should be a close and safe location to stop your car (lot or alley) – You shouldn’t have to stop on a public roadway.

Other Neighborhood Foxes

We’re glad that foxhunting is becoming popular in NTX. You can also hunt these other neighborhood foxes:

UTD MicroFox – The UTD Amateur Radio Club (K5UTD) places a micro-fox on campus most weekends. It transmits CW on 433.1 MHz. Battery should last for 24 hours. The fox is outdoors, located somewhere in the main academic area of the UTD campus!

FREDDY THE FOX – Built by KI5GRN, Freddy hangs out in McKinney (usually) and can be heard on 434.5 MHz.

SACHSE– We have rumors of a fox in Sachse. Reportedly, the fox is on 146.565MHz but very low power.

WHITE ROCK LAKE – There are at least two foxes “Rocky” and “Bullwinkle” close to White Rock Lake every other weekend.

DENTON – DCARA is now sponsoring foxhunts in Denton County – they have a mailing list for info.