the Poppet 500 milliwatt AM transmitter


Posted on Feb 7, 2014

The Poppet` is a half-watt AM transmitter designed by Mr. Doug Gibson of England. The original design was published in issue 84 of SPRAT, newsletter of the GQRP Club. The version shown here incorporates changes suggested by Steve Hartley and others. Although it was designed to work with a microphone and to be used in the 160 meter band (1800-2000


the Poppet 500 milliwatt AM transmitter
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kHz), the Poppet can easily be modified to work in the 1600-1720 kHz end of the AM broadcast band and work with a line level input from a mixer instead of a microphone. Construction details are not critical. The LM386 and the output transistor will need heatsinks. The circuit can be built "dead bug style" with the modulator chip stuck upside-down to the copper circuit board for heatsinking. To modify the Poppet for neighborhood broadcasting in the 1600-1720 kHz frequency range, either increase the capacitance of C8 to bring the VFO`s frequency down into the broadcast band, or replace the VFO with a simple crystal oscillator or PLL synthesizer. The microphone pre-amp stage can be omitted if the unit is used with a line-level audio source such as a mixer or tape player.




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