Radio circuit diagrams

Bug Detector

This circuit can be used to "sweep" an area or room and will indicate if a surveillance device is operative. The problem in making a suitable detector is to get its sensitivity just right; too much and it will respond to radio broadcasts, too little sensitivity and nothing will be heard.

Band 2 Preamplifier

This is a VHF amplifier for the Band 2 Radio Spectrum tuning approximately 88 - 108 Mhz.

The ATL-3 Loop Antenna

This antenna is the result of long term development and user feedback.

FM Stereo Transmitter

This is a small stereo FM transmitter. Output can be tuned from 88to 108Mhz and the transmitter can be battery powered or be used with the low voltage power supply on this page.

Portable FM Transmitter

A portable FM transmitter that can be used to replace a FM microphone.

2 Transistor Transmitter

A compact 2 transistor transmitter for use at VHF frequencies.

Antenna Tuning Unit

A simple passive (no power required) circuit to match an antenna to a radio receiver. This will be a useful addition to the short wave listener, but in addition a medium wave coil is almost used to tune the medium wave band.

SW Aerial Amplifier

A radio frequency amplifier to boost SW reception. Frequency range approximately 5 to 20 MHz.

Automatic Repeater

It is a self powered (audio derived) repeater circuit for receiving a signal and re-transmitting it via the other radio.

30 Watt VHF Amplifier

The 30 watt amplifier schematic shown below provides an appropriate power boost with an input of 4 watt up to 6 watts. The circuit is designed to cover 88-108MHz FM Broadcast Band.