144MHz Amplifier W6PO design
Introduction
The 3CX1500A7 is a nice valve to play with. Some more talented individuals use tetrodes, but triodes are surely the way forward for the majority, provided that you have adequate drive - about 60W.
Results?
The plan is to rebuild this into a slightly shorter unit - cutting off the plate lines beyond their grounding points, so that it all fits into one 6U high unit.
The W6PO design was straightforward to get going, the tank resonating at 130MHz before adjustment of the anode lines. I had more trouble with the cathode circuitry, and couldn’t use the original design.
Control circuitry, bias and filament supplies are placed in a separate unit. The intention was to be able to power a second amplifier on HF, but that project has not happened. Now I have a 3CPX1500A7 in the VHF amp, so the original valve is spare so the HF project could happen..
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I treated myself to a new Bird 43 power meter and 1000C element for the final tests. Once it became apparent that there was sufficient RF to end-stop the Bird 43, I had to buy a 2500C element. I have paid more for the power meter and its sampling elements than I have for the amplifier! Be aware, once you have a Bird 43, you’re in danger of collecting more and more sampling elements for it..
FT-225RD, 25W in gave 600W out.
SD1416, 70W in gave 2.2kW out.
