This Wideband VHF FM transmitter will output approximately 100mW of RF power. The unit has to be connected in series with the incoming twisted pair cable, this is easily done by chopping one wire and connecting the unit between the two ends. The transmitter reteives its power from the telephone line hense the unit only transmits when a conversation is taking place. The frequency can be tuned between 90 and 110MHz with 5turns on L1 using 22SWG openly wound with a 10mm di. With a 12cm wire for an antenna upto 1.5Km range is possible. The 12pF trimmmer sets the output for maximum sigal and frequency. It is Ideal to tune up this circuit using a wave detector meter placed a few inches away from the transmitter. I have a circuit on this site.
This page was updated on 20th March 2000.