Transmitter v1.5

After flying with my transmitter v1 for about 4 months, I thought it was time to upgrade. The biggest reason being that the PlayStation joysticks I ended up using were closer to digital than analog. What I mean by this, is that the joysticks had a very large dead zone and also the control saturated quickly. Moving the stick from the center to the right would change output for the first 1/3 of the range. It would then give a nice proportional output 1/3 of the range after that, and the last 1/3 of the range would again not change the output any further. This was not that big of a problem with an airplane, but I wanted eventually to fly also multicopters and I thought this was something that would really cause problems with them. Also, the way you trimmed the control in the old interface was horrible and I wanted to change that.

Randomly browsing through DealExtreme I came across this. That looked like something I could use! I would just remove all the electronics that were already in and replace them with my own. It would even have mechanical trims in place. Sure it was a bit on the expensive side, but the whole idea of building my own transmitter to save money was long gone anyway.

After a couple of hours of tinkering, I had removed the digitizer and transmitter boards from my old transmitter and moved them in the new enclosure and everything was working well.

Inside the transmitter it's a big mess of wires.

Front view of the transmitter. That antenna sure looks suspicious...

I originally used a small rubber ducky antenna with this transmitter and I never had any bigger problems with that during a couple of months of flying. I was planning to do FPV in the near future, however, and wanted to be sure my transmitter could do at least 1 kilometer. So I did what any sensible person does: I designed and built a 10dBi gain Yagi-Uda antenna and hot glued it to the back of the transmitter.

It is very awkward to carry this thing around. Flying with it is no problem though.

Based on RSSI (receive signal strength indicator) data sent in the plane telemetry, the antenna adds around 9 dB to the signal strength (so only 1dB less than what it was designed for), which is surprising considering it is made of scrap brass tubing, a couple of scrap pieces of pine and a lot of hot glue. Also the only sufficiently long piece of 50 ohm coaxial cable I could find in my scrap heap was RG-58, which I would not really consider ideal for the job. Like half of the stuff I do, this was first made as a prototype, which was to be refined later. But like always, this later never came and I was stuck with the prototype. And range wise, I've never run out of range with this thing. A simple extrapolation (with 5% packet loss) from the RSSI and range data of the telemetry would suggest a 6 km range at 100mW transmit power.