R1 = 10K (brown-black-orange)
R2,R3 = 100K (brown-black-yellow)
R4 = 470 ohm (yellow-violet-brown)
C1,C3 = 4.7pF (4p7), ceramic
C2,C4 = 4.7uF-16V, electrolytic
C5 = 0.001uF (1nF), ceramic
C6 = 470pF, ceramic
Q1,Q2 = 2N2222, NPN transistor
L1 = 1uH, variable inductor
Mic = Electret mike, 2 wires
Q1 amplifies the input signal via C4 from the electret microphone.
Q2 acts as an oscillator and the signal coming off C2 is fed onto the base of Q2.
L1/C1 is a so called 'tank' circuit and operates in the 88-105MHz band on your regular AM/FM radio dial.
L1 is a 1uH variable inductor coil to be able to tune it a little bit, and the range of 1uH is approximate.
The antenna can be as simple as a 8" (21cm) piece of wire of any kind.
Copyright © 2003 - Tony van Roon