The system is based on the very cheap and easily obtained at rallies gunn diode doppler motion sensor from scrap burgular alarm units. When purchased they are usually tuned to about 10.685ghz and will pull down into the 3cm band with one screw adjustment. The power generated is about 10mW. This may seem very small but it will certainly travel under the right circumstances. My best results have been P5 at 94 miles using an old 35cm bsb dish increase the forward gain. This was a sea path from Wells on the Norfolk coast to Bridlington on the Yorkshire coast using a propergation mode called sea surface ducting. Other enthusiasts have achieved greater results between the UK and Holland.

A view of one of my self contained transmitters. The larger pcb is the modulator. This requires 12v, audio and video (which can come from a domestic cam-corder). The black and grey twisted wires go to the Gunn module. This board is a kit supplied by Bob Platts who has done a lot of pioneering work on 10ghz. It takes standard 1vp-p video and applies it to a dc regulator giving 7v to the Gunn diode. The audio in is fed to a 6mhz oscillator which is mixed with the video giving standard intercarrier sound. The other board supplies an audio test tone and vertical black and white bars which make the unit a useful signal source. There is also a small circuit which monitors the 12v rail because if batteries are being used and they run down the Gunn diode will be destroyed if its volts drop below 5v so the monitor removes the Gunn supply if the main supply drops to 10v.