I was inspired by the OpenLRS project to make my own UHF remote control and telemetry for my FPV planes, but much cheaper!
You can get the RF22B 100mW (20dbm, many km range) tranceiver modules from HopeRF very cheaply, I got 6 for ~30 Euro. They are great transceivers, and there is a arduino library for them: RF22: RF22 library for Arduino. In the example code, there is a spectrum scanning demo. I changed the code a bit and wrote a PC program to make it easier to use:
250MHz to 960MHz sweep:
Close up at 434MHz:
Pictures of the board:
The PC program (in C#, a modified version of my plotting program: http://arduino.cc/forum/index.php/topic,80462.0.html) and arduino code are attached.
Have fun!
Edit: The arduino code posted here may have some problems, see this post for the new code: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module - #58 by system - Exhibition / Gallery - Arduino Forum
New version of PC program: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module - #64 by system - Exhibition / Gallery - Arduino Forum
Update on potential board problem: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module - #126 by system - Exhibition / Gallery - Arduino Forum
New version with telemetry support: Cheap UHF spectrum analyzer (and RC tx rx) using RFM22 module - #135 by system - Exhibition / Gallery - Arduino Forum
RF22SpecScan.zip (193 KB)
rf22_specan.zip (1.24 KB)