DERBY AMATEUR TELEVISION

GROUP

Radio Shack

Whether units have automatic frequency control or are crystal controlled is next to impossible to determine without ordering and actually examining them. Radio Shack used to sell 4 channel Wavecom 2.4 GHz FM Video Sender units that were known to have a crystal controlled PLL circuit. However Radio Shack now sells it's own brand of identical looking video sender with only a simple free running voltage controlled oscillator with channel selection done by simply selecting different resistors in a voltage divider circuit.

X10.com used to also sell Wavecom Video Sender units and the advantages of 2.4 GHz FM video transmission. But now I see nothing about Wavecom or FM on their web site which provides no useful information about the units they sell other than they operate on 2.4 GHz. I was asked recently for my comments on X10 equipment, but until someone leaves me some X10 cameras and receivers for a few days to work with, what X10.com now provides is anyone's guess. I did see one of their cameras advertised as having a CMOS sensor and suspect that they all are probably less expensive CMOS cameras. As for the units pictured here, I did find one easily corrected problem.

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. An old 35cm bsb dish will increase the forward gain. Other enthusiasts have achieved greater results between the UK and Holland. 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.