eCircuitbook

Transmitter Parts:

R1, R4, R6 10K resistor


R2 1Meg resistor


R3 100K resistor


R5 100 ohm resistor


R7 1K resistor


C1, C2 0.1uf capacitor


C3 0.01uf capacitor


C4 4-40pf variable capacitor


C5 4.7pf capacitor


Q1, Q2 2N3904 transistor


L1 8-10 turns of 22gauge wire around non-conductive 1/4" diameter form


Elec Mike Electret Mic

This miniature transmitter is easy to construct and it's transmissions can be picked up on any standard FM receiver. It has a range of up to 1/4 of a mile or more. It is great for room monitoring, baby listening, nature research, etc. L1 is 8 to 10 turns of 22 gauge hookup wire close wound around a non-conductive 1/4 inch diameter form, such as a pencil. C4 is a small, screw-adjustable, trimmer capacitor. Set your FM receiver for a clear, blank space in the lower end of the band. Then, with a non-conductive tool, adjust this capacitor for the clearest reception. A little experimenting and patience may be in order. Most of the parts' values are not critical, so you can try adjusting them to see what happens.