What's next?

As far as we've come, there's still a long way to go. Tomorrow, (or as I write this, later today), we will be conducting the first round of range tests.
These tests, using our prototype receiver and transmitter, will give us our first chance to see what the units are capable of. Part of tomorrows plan involves making a half-wave dipole antenna to go on our receiver, which is essentially just some coathangers cut to the correct length for our centre frequency. Confirming range is an important step to qualifing our hardware for flight - theres little point in putting all this extra weight on board if we lose the signal before the balloon loses GSM. Lets hope for some good results...

Assuming we get the results we require, the next stage will be to purchase a suitable GPS receiver. Some research has already been undertaken in this area, so we are reasonably familiar with what will (and what won't) do the job. Once again, its no easy task. We have many contraints that consumers normally wouldn't think twice about including weight, power use, minimum baud rate and ability to customize NMEA data. Just to make make things that extra bit harder, we also need a device which implements COCOM aka ITAR restrictions properly. Every GPS receiver sold in world has a restriction built-in to prevent a 'home-brew' cruise missile. The exact implementation should shut down the GPS device should it exceed 60,000ft AND be moving at greater than 999 knots. Unfortunately, most GPS developers code their firmware with 'OR' instead of 'AND' - no doubt assuming neither are very likely anyway. The upshot of all this being that as our balloon will be going above 60,000ft, we need to make sure that our device doesn't bug out or we'll never see our payload again!

Still, lets get through tomorrows testing first....