FC's Micro Power FM Broadcasting Circuits

Power your FM transmitter with solar power by using a CirKits kit.

SCC3b SPC3 DAS1 LVD1 BVM1
Solar Charge Controller Solar Power Center Dark Activated Switch Low Voltage Disconnect Battery Voltage Monitor

FM Bugs

High Quality Stereo Modulator

This FM stereo matrix generator circuit can be used to produce stereo modulation for a variety of mono FM transmitters.

FM Broadcast Antennas

A good antenna and low-loss feedline are essential for making the most out of your measily microwatts.

My Hula Hoop Ground Plane Vertical Antenna is an efficient antenna that is easy to build and align.

This J-pole design works very well if you tune it up properly. An SWR meter is a must for setting up this antenna.

FM10a Stuff

Here are some utility circuits for use with the Ramsey FM10a and other small FM stereo transmitter kits, such as those that are based on the Rohm BA1404 IC. The FM10a kits tend to put out a low-quality, broad-band signal. This is not a big problem with a 5-10 milliwatt signal, but amplifying the output of such kits beyond 100mw is a bad idea, as the amplified signal can cause interference with other radio services, drawing unwanted attention to your hobby station.

If you want to transmit with higher power, find a better quality transmitter such as the Free Radio Berkeley Mono PLL kit, and build my circuit for an FM Stereo generator (above).

Here are some tips on squeezing the most performance out of an FM10a kit:
Five Essential mods for the Ramsey FM10a

Also see my constant temperature circuit, can help to reduce frequency drift in transmitters like the FM10a. Better yet, just get a PLL-based transmitter that does not have the frequency drift problem.

Audio Mixer for the Ramsey FM10a in GIF format (16kb)
Description of the FM10a Audio Mixer

Useful Links


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