I am looking for a robust and reliable digital telemetry link between a solar car (which may be up to a mile away, on track) and not necessarily line-of-sight. Requirements listed below:
* >1000 baud preferred (100 baud minimum)
* Simple to implement (we don't have lots of development time left for the project)
* 1 mile distance with obstructions
* Legal (I don't want to piss off the FCC :P)
* efficient (let's impose a... oh, IDK... 5W transmit power for the car? Ok? Ok.)
What I have considered / am considering:
* Other teams have used the popular 900MHz Xbee pro UART radio modules for this purpose, but the distance seems to be quite short / limited. The advantages include eese of use, as it acts as a nearly-transparent UART bridge, but it appears they may not be good enough for this application.
* 433MHz? I know lower frequencies tend to propagate further for a given power, would 433MHz be preferable over 900MHz? I can't seem to find many devices beyond small keyfobs and stuff using this band.
* 72MHz? I know this band was used for old-school RC transmitters, can I repurpose it for telemetry? Have not looked into it too much. Doesn't appear to do any sort of frequency hopping or other fancy stuff either.
* amatuer HAM / CB / radio frequencies? I think this is the most robust solution but probably requires the most effort too. I and the rest of the team would need to get licenced (although honestly I want get licenced to mess around with this stuff anyway) and we would probably need to design a system around some form of digital encoding. There appear to be a lot of different methods, but are there any that meet the throughput requirements?