809 RF Power Amplifier with triple 2A5 Exciter


The exciter for this transmitter is the triple 2A5 transmitter outlined elsewhere on this web site. It is the lower deck in the above picture. The tank coil of the 2A5 buffer tubes is link coupled to the grid circuit of the 809 PA. A one turn link is used at both ends. With 600 VDC on the plates of the 809, the PA will produce about 25 -30 watts output. For more power output, I am in the process of building a higher voltage supply for the amplifier, as typical class C telegraphy operation is at 750 VDC. The transmitter is keyed at the 2A5 buffer stage.

A link to the schematic can be found here: schematic

Operating Notes/Parameters: Under Construction!


View of the power amplifier. At the left is the 809 tank circuit and neutralizing capacitor. The plate circuit is shielded from the grid input circuit by a piece of grounded aluminum sheet. The grid input coil is visible to the right of the shield. Note that the tank circuit is built on a small platform to keep lead lengths short.


Closeup of the final amplifier


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