Here is a collection of schematic diagrams for radio transmitters and transmitter amplifiers. Although circuit components are labelled (and can be built easily), schematics are for educational purposes only!!! Operation of some of these devices may require licensure. If you wish to experiement with RF transmitting circuitry without violating regulations, use a dummy load in lieu of an antenna.
Note: This is strictly a collection of schematics, sent to me by readers. Except for the FCC Part 15 Compliant Three Transistor Mic, I have not built any other circuits on this page and have no way of knowing whether or not they actually work. At present, I do not have any of the illustrated transmitters in posession. If you wish to build any of the circuits below, be sure to check with local law authorities on their legal implications first. Although small transmitters are ofen referred to as "bugs", such devices are NOT to be used to record conversations without the consent of persons involved.
I will be adding to this library as more schematics become available. If you have diagrams to contribute, please email me at achanne at sfu dot ca.
Many simple FM "bugs" (i.e. 2-3 transistor 88-108 MHz microphones; non-crystal types) can be modified for use on higher or lower frequencies. To transmit above 108 MHz, simply reduce the number of turns in the inductor coil of the tuned circuit. To transmit below 88 MHz, increase the number of turns and/or add a few more picofarads in parallel with the tuner (if it's a variable capacitor and not a variable resistor as in a voltage controlled oscillator).
Solid State Transmitters:
Tube-Type Transmitter Amplifiers: Coming Soon!
Other Related Links of Interest:
FM Wireless Schematics from "Educypedia"
SSRsi's Miscellaneous Communications Page
More transmitter-related links wanted. Please email me at achanne at sfu dot ca to establish a reciprocal linkage.
Updated: March 8, 2008
March 29, 2008
March 31, 2008