Sending binary data over FM 144.650 MHz


This is about a wheater balloon project.

I need to send low speed binary data from the ballon (10,000 meters max altitude) to a ham vhf receiver (FM 144.650 MHz).

I'm quite good for digital electronic, but not analog...

I think I need an oscillator and an amplifier, but I don't know exactly how to do it.

If anybody have an idea...

(the design must be really cheap, because chances of retrieving the balloon is poor)


Might want to ask on a forum for Amateur radio enthusiasts for help on making radios.

I know theres kits and howtos out there on the internet for building FM transmitters, but typically they are low power and for a weather balloon you'll probably want to use a good amount of power.

You have the choice of sending AFSK (audio frequency shift keying) or carrier shift keying. Using AFSK is a lot easier to receive than simply changing the frequency. Especially at low bit rates.

Do you know what protocol you are going to use?

We are going to launch a weather balloon too.
We decided to buy a commercial radio.
Here are a few examples:

From the software point of view, we maintain an RTOS which have an AFSK modem and AX25 layer ready to be used in order to send/receive APRS packets.

Here is an example project which uses an Arduino board to encode/decode APRS packets:

The required hardware is very minimal!