[amsat-bb] High Altitude Balloon micro battery reccomendation

[Skyler F]

I am going to send up a few micro beacons (milliwatt HF CW transmitters)
probably using Walmart balloons and thin wire as the active antenna/payload
string.

The CW beacon RF module is a really simple oscillator that drifts a certain
amount with temperature - that way I can tell how cold it is based on the
received frequency from on the ground. An ATtiny or something similar will
probably be used to keep the beacon legal and send out CW every 10 mins to
break the carrier.

So the whole RF module and beacon is extremely light, basic
transistor/crystal oscillator + ID chip so I don't have to worry about
recovery. The only consideration is the battery. I will probably have
something operational between 3 and 7 volts, so I am thinking about just
stringing a few watch batteries together. Is there a certain recommendation
for low temperature operation miniature batteries? I need to make this
payload as light as possible.

The goal is the cheapest Amateur Radio balloon project where recovery is
not a worry. Signal strength reports across the country as well as wind
predictions can get a good idea of where the balloon travelled. I can then
match this data up with the daily National Weather Service launch data to
determine how high my balloon went based on temperature.


73
Skyler KD0WHB