Just a quick mention of the MiniMod, a micro-power pantry transmitter that appeared in the Winter 2011 BVWS Bulletin, that I've just finished building.
This is an elegant little circuit that performs brilliantly, and the audio quality is excellent, so congratulations must go to the designer Ian Liston-Smith. I built mine on a piece of matrix board less than 2" square and housed it in a Maplins plastic case, the most expensive item in the parts list! The specified coils are still available from Spectrum Communications for 90p each. I had most of the passive components in stock or donated by friends, and I only had to buy a 2N3819 plus the coils. All told, I don't think the cost exceeded £10.
Apart from having to trace and rectify one wiring error
it worked first time. I added an LED indicator fed via a resistor and five diodes to give me an "on" warning light and battery state indicator, which goes out below about 5 volts. The output is good enough to cover one or two rooms with five feet of wire as an aerial.
A couple of photos are attached.
Phil