K1FM Pico Balloon – Part Three

The Balloon payload is finally finished, and practically ready to fly (I need to solder a capacitor at the bottom, but that’s a one minute job).

For the software I ended up forking and modifying OrionWspr, which I renamed GeminiWspr. As it is now, the beacon will transmit on every available WSPR slot after doing GPS calibration on startup and recalibrating every 20 minutes. On minutes 00 and 30 the beacon will also transmit a CW telemetry message on 14.099 MHz.

Power is supplied by 7 solar cells, providing about 3.6 volt. A 1F supercapacitor, fed by a low voltage dropout diode, is applied to guarantee a minimum of power continuity. Current is plentiful, to the point I could have actually split those cells in half. That is somethings others have managed doing but when I tried I shattered the cells each time. I’ll need to ask around for next time.

Here is the finished payload:

I must admit that it seems a bit heavier than I have originally planned for, especially after considering that the actual board (after removing the disposable header) weights just 2.81 grams.

Finding lift gas has been a challenge. The logistics of gas procurement, storage and transportation to the launch site aren’t trivial when you live in a big city apartment and you do not have a car. Long story short: I had to forget about Hydrogen and reverted to Helium.

I am now waiting for a launch window.