A very nice $0.01 solution.
Except it kills how Allard is doing CW.
He unbalances the carrier by putting 5v into a 10k resistor that goes to the top of C107.
Maybe fix this PTT pop somehow in microphone preamp so we can continue to use Allard's CW method??
Could transmit CW like Farhan is doing it on the uBitx: ?Move the VFO to the transmit freq and unbalance the first ring mixer. ?Those three mixer ports got stirred up considerably on the uBitx, though it is otherwise the same mixer as on the Bitx40. ?Is there a some simple way to do this without a significant hardware hack to the existing Bitx40 boards?
Don Cantrell was injecting RF at the transmit freq from a spare Si5351 output, ?Could key it by writing to an Si5351 register, so could be done with just a resistor. ?But this method does not offer an easy method for key shaping, whereas the mixer unbalance schemes used by Allard and Farhan do. ?With Allard's it's C107 that gives key shaping, on Farhan's uBitx it's C1. ?Though I think the uBitx's C1 may need to be considerably larger (maybe 1uF, though I'm not sure how the BiDi amp affects this) to give appropriate rise and fall times to the keying envelope. ?Allard's original 47k resistor was probably about right for the 0.1uF C107, the move to 10k makes the edges a bit fast, but we could go back to 47k if the BFO is driven from CLK0 and thus can be centered in the crystal filter passband. ?Keying envelopes may not matter much for a one off rig at 5W, but for wide distribution and the inevitable use with QRO amps, I'd want clean CW key shaping.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Wed, May 31, 2017 at 08:13 pm, Raj vu2zap wrote:
See my solution:
/g/BITX20/topic/ptt_pop_hack/4460108?p=,,,20,0,0,0::Relevance,,PTT+pop+raj,20,2,0,4460108
?
