Two-tube AM Transmitter

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After several circuit failures in previous transmitter projects (trial and errors), I finally completed a working transmitter. The transmitter's design came from several ideas, especially from Phil's Li'l 7 Transmitter design. My transmitter works strongly around 1400kHz on the AM band, and consists of two tubes: 6J5 and 6SA7. Below is the schematic diagram of the transmitter.

The antenna coil was salvaged from an old radio's 456kHz oscillator circuit. One coil is generally twice the resistance of the other coil - the higher resistance coil is the larger coil in the schematic. ***NOTE: If the coil does not oscillate, reverse the connections on one of the coils.

The 6J5 is actually a triode designed for general purposes. However, the tube serves as a low power half-wave rectifier in this circuit. The power supply provides about 140VDC loaded.

A trimmer capacitor is optional, it allows you to change the frequency of the transmitter in a small range.

CAUTION: This transmitter is NOT isolated from mains and can shock.

Pictures of the two-tube AM transmitter:

Two-tube AM transmitter

Bottom view