We Went on a Fox Hunt! A Ham Fox Hunt

A Ham Foxhunt is an activity that Amateur Radio operators do where a transmitter is hidden in the community and you have to go find it. This is an important skill to learn as you can use it to find people who are lost or a crashed airplane or even an illegal transmitter.

So we (about a dozen of us) met at a parking lot and got our instructions. As we just got our licenses and haven't been able to build or buy a directional antenna we were lent one. We all got our first bearings, in the NNW direction. The signal was too weak to even hear with our handheld.

My wife and I hoped on the interstate and ran a few exits to shoot another bearing at a big box store that had some open space next to it, that I knew of. After getting a nearly West bearing we just took off down the street to try and box in the contact. We knew the next major street north was the boundary of the search box so we could box it in as we got closer.

With my wife watching the signal strength meter on our handheld she saw it rise and fall. So I turned North and came back on the boundary street to see if it had been north or south of the previous road.

Well, it pegged the meter as we drove past a supermarket. I turned and headed south to see if it dropped off after we passed a golf course. We went back to the supermarket and there was a little plaza that just seemed to say "It's right here." Just as we pulled in I saw a couple of the others wandering around with their Yagis, so we knew we were close.

While my wife kept our daughter entertained and out of the parking lot with some of the other children, I went looking for the "Fox." We knew it was a green ammo can but we were so close that the meter was pegged no matter which way we pointed. So I got out our little handheld and a baking sheet to try to find a null but there were too many reflections from the buildings us to go any good. We had been instructed that we could replace the regular antenna with a paperclip but we could find ours, we still needed to find a way to strongly attenuate that signal.

Then I remember we had covered the potato salad with aluminum foil. I wrapped our handheld in the foil and that worked great. Moving South toward the golf course it went down, tried west down again, back north and it got stronger.

At this point I realized I needed to use my eyes instead of my radio. Sure enough hidden in the junipers next to a tree was a little green box with an antenna.

It had taken us 44 minutes to find it. Second place. Most of us had come to the parking lot at virtually the same time. The leader had only gotten there about 2 minutes before. The last place team had caught a building reflection on their second bearing and that had sent them in the totally wrong direction. It was funny when we finally saw him, as we were wondering where they were, he was on the hill behind the store pointing his Yagi right at it but it was the rear lobe that he was catching it so he was looking the wrong way. Then we all went to the picnic.

Some lessons learned: We need a directional antenna to do this kind of work. An attenuator to help with the close work or a really lossy mini directional antenna out of paperclips or something.

Afterwards at the picnic we were looking at the "Fox." Written on the outside was a simple message explaining to people that it was a piece of Amateur Radio Emergency Training equipment. It doesn't come out and say it isn't a bomb but it turns out these kinds of activities get peoples attention, my wife answered a question of a passersby during the event.

The Fox itself was an old handheld modified with a hacked digital timer, a few other electronics and a large battery to run at 400mW or 1.4W. We were discussing making some of our own, this one was bought from another ham. All it does is send a morse code signal in FM for a short period of time. We brainstormed a bit and we figure a microcontroller could do most of the work of generating the signal and controlling the timing, we could hack one of those iPod FM transmitters up to our band and an output amp to boost it to 1-1.5 W instead of the 100mW as is typical of those iPod FM modules.

Fun stuff.