I'm looking for some ways to transmit pictures from a high altitude balloon.
Is there any open-source software for dealing with this over radio?
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Sparkfun also sells some.
So now you at least have a physical layer to get stacks for.
Maybe open source does not get the quality you are looking for here, but functionally changing the modem would, in theory, not be necessary.
Some hints - For transmission from balloons you are likely to wish to minimise:
a) Weight & b) Power Requirements
To minimise these you usually need to minimise bandwidth and allow for transmission errors so first I would suggest considering using a good compression that also allows you to see what is coming down - I would look at progressive jpeg encoding - plenty of Open Source tools to support this.
It's a US $20 Arduino board with 1kmn wifi range (which it should reach vertically, as there are unlikely to be obstructions)).
That's about it really, so now for the obligatory graphic
[Update] if necessary ... a bunch of balloons, spaced 0.9km apart vertically, with wifi repeaters
I have had lots of fun with Skywave’s offerings (they have now rebranded as OrbComm), and you might like to look at the IDP_800.
Read the datasheet.
Mass: with batteries: 1.3 Kg (with integrated antenna Dimensions : 43.2 cm x 14.7 cm x 2.5 cm and it runs on 6 AA batteries, which can be bought almost anywhere.
I send only one 50 byte message a day & they tell me that I can except a three year battery life. Their units generally cost US $500 - $1,000 (with discount for bulk purchases), and their airtime rates are competitive.
The device has built in GPDS and is fully programmable in the LUA scripting language.
Note that this is not an open source software solution - is that really what you want?