FFM - (Finally) Frequency Modulated

Throughout the entire term, I was having a really tough time making one of my main goals actually happen. That goal was FM transmission over a fairly long distance, and even though I was able to get my AM transmitter working for a short time, it was also only for a short distance, so when I ordered ten FM transmitter bug kits from QKits.com, I was pretty excited. These kits were supposed to be able to transmit up to 100' on a stable frequency, and so I decided to get them and use them for my project.

The kits looked like this before they were assembled:The red wires on top are the battery connector and antenna wires. The interesting thing about this kit is that the inductor is actually printed right on the circuit board, and the antenna can tap into the inductor in two different spots. If you use tap A, the transmitter can broadcast a lot further, but the signal will drift quite a bit more. If you use tap B, the transmitter should transmit for 100 feet, but the signal will be much more stable, which is why after I tested both, I decided on using tap B, since my machine can't constantly re-tune itself.

This is what the transmitter looked like after it was all soldered together.

The whole thing is extremely small, and could easily fit inside a small mint tin, but I haven't gotten around to that just yet.

After I got a few radios together, I got my younger brother to come in to studio and be my helper monkey. Together, we found that the transmitter could easily reach 100' on tap B, but if we had to go through doorways in the Russell building, the transmission would instantly stop. The metal doorways don't allow the radio waves to pass through, so it was decided that I would have to have all of my transmitters inside the Russell building, no matter what. It was encouraging, though, to see that it could also quite easily transmit through the concrete floors in the building, which was pretty exciting.

When we tried the radios on tap A, the signal drifted about 5 mHz either way, which is way too much drift in much too short a time.