Sunday, 11 May 2008
Regen RX stillborn, 160m TX improves
The regenerative TRF receiver didn't work, and I'm not especially bothered. I'll fiddle with that when I have more time, but right now I want to get the 160m transmitter running right.
The SSB transmitter now has an output of 1.5W PEP. I'll accept this as it's final power level, because I wish to prove that such moderate power can be viable for communication. I've aready logged contacts at three miles using 100mW, and I expect to be able to cover a radius of ten with the 1.5W now available.
The figures for the drain current in the PA FET are quite ordinary. I've set the quiescent bias current at 20mA, and the drain carries 300mA average on full output. The FET used was an IRF510; in hindsight, this is a waste of a good HF FET, and an IRF640 or BUZ11 would have served just as well. However, I have a second VXO crystal aboard which covers the upper part of the 80m band, and here the IRF510 would do better than a motor-switcher FET. The radio is designed to work up to the 40m band, using an external oscillator, so all bases are covered with this PA.
I put out a CQ call on 1940kHz at 1910UTC, but nothing came back. I'll try later, after dark, and hunt around a little more avidly.