Re: More questions
Gary,toggle quoted messageShow quoted text
The carrier burst on PTT is due to the C122 charging up through D15 or 16 unbalancing it and allowing a leak.
Quick fix is put a 0.68uF cap from the common of D15/16 to the atten pad R39. A track has to be cut.
If your board has a trimpot there then you can tombstone the pot and add the cap.
A 1K resistor across C107 helps.
The leak is almost eliminated.
At 19/10/2017, you wrote:
I tried the relay idea Brent, and it did nothing, so don't go hacking your board on the hope this is going to fix your problem. I still see a burst of full carrier for ~ 6 ms immediately after PTT is applied. I see the same result in CW mode, except there's a pause after the burst before the carrier comes on for the first code element is transmitted. The timing is almost precise on this, but I haven't found anything in the code that seems to correlate with it. The 6 ms does correlate with the relay switching speed, but it seems I'm puzzled on this issue again. Either I'm still overlooking something, or I botched the hack on my board.