On 2021-06-20 19:22, Ashhar Farhan wrote:
Jerry,
It would be a very extensive effort.
1. Given similar power levels, a 2N7000 in place of the antenna relay
should work. A few more transistors can isolate the rx signal path.
This is the easier of the wins.
*** How about PIN diodes? Yeah, they're expensive, but apparently 1N4007's
work fine. See starting at page 53.
Also see
...in which Don Huff W6JL goes into the technique in great detail, documenting his homebrew switch
at the 600W level.
Hans Summers does something really smart with his 50W amp - he rectifies a smidgeon of the amplifier output RF with a voltage doubler to produce the "off" bias for the switching diodes.
2. Timing. A particular sequence of things have to happen. On key
down, the rx audio has to smoothly switch off, then the rx amplifiers
power should turn off and the bypass caps need to be discharged, the
tx circuitry has to power up. The sequence has to reverse on key up.
*** This is surely where the majority of the work would be.
4. The LPF relays should be constantly powered up (even on rx). These
may wear out the relays.
*** Why? Coil heating? The relays should be really loafing, sitting there
energized in receive. Of course, it wouldn't do much good for battery life.
- Jerry
