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Jeffrey Bauman wrote:
I'm considering building the am/cw transmitter in the 1966 handbook (probably in others, too). It runs a single 6146 in the final. I am curious if anyone has ever built that rig. If I build it, it will probably be with an outboard power supply, and a single switch for input / tank band switching. Not that exact rig, but I've built similar 6146 transmitters. One gotcha with the oscillator-final setup is that you may not end up with enough drive on 21 and 28 MHz, if those bands matter to you. The Eico 720 improves on this by using a buffer/multiplier. I like the Eico 720 design, but a weakness is lack of VR regulation leading to chirp (especially if you multiply up.) The handbook transmitter doesn't include a clamping tube, so if for some reason you have no or insufficient drive you can find your final tube dissipating too much power and melting down. But, elsewhere in that handbook you will find several examples of clampers. Bandswitching and plate choke resonances are easier to deal with if you limit yourself to 2 bands or so (say 80 and 40 or 40 and 20). Every handbook from the late 40's up through the early 70's has a CW transmitter rig of similar spirit, earlier ones using a 1625 or 807 or something similar. Tim. |
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