High Quality Audio FM Transmitter Circuits
In a flash of inspiration, I thought visitors to SpyReview might appreciate circuit diagrams for various surveillance circuits. Therefore I have started a new category of posts on the site called “Circuits” (duh!).
To start things off, here are 3 FM audio bugs, designed to be powered by batteries. One is low powered, and 2 are high powered. The latter two, due to the 3 transistor stages, will be more stable and therefore will not drift in frequency as much as the 1 transistor version. The designer is a well-respected RF circuit engineer.
Audio Bug Circuits:
Wireless Microphone by Harry Lythall – a basic FM bug using a single transistor and common components. Can easily be made into a tiny package.
Wireless Microphone 2 by Harry Lythall – a low power FM bug with 3 transistors for excellent stability. It will probably eat batteries though.
40mW FM Transmitter by Harry Lythall – a 40mW high power FM bug with 3 transistors and relatively few components. This will eat batteries too.