Since abandoning a software hack, I've attempted ferreting out a hardware hack to get rid of the PTT burst, but. I've only been able to cut it back, However; in so doing, I have measured the burst and discovered that it occurs in both CW and SSB modes, and in both cases the burst is consistent and decays after approximately 6 ms. In CW mode there appears to be a built in 15 ms startup delay, which includes the TX-RX delay of 5 ms after keying the relay, As I recall, the switching spec for the relays is 7 ms max., which means PTT_sense is visited within less than 10ms after PTT is activated. Even better... with your scheme, the code will be 7 ms into the task of shutting down the clock before the relay finally switches, bringing the delay down to near zero. I will be giving this a try while waiting for Allard's next release. As gate keeper of the software, he will know the fastest path to toggle the clock.
I'll be looking at implementing the AGC next also. If I understand your suggestion on this, I don't think it will work. The 5V PTT_Sense goes to zero when transitioning to receive. Assuming this is what you wish to sense, this would turn the fet off, causing the audio to go to maximum. His AGC voltage is positive, but it enables him to use the logic FET, which turns off at zero volts.
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Gary, N3GO
