locked Re: IC-7100 FT8 transmit timing problem.


Martin G0HDB
 

On Sat, Oct 24, 2020 at 08:04 PM, Bill Somerville wrote:

Hi Martin,

the audio click you are hearing when using CAT PTT is probably due to the PTT not being asserted until after the audio from WSJT-X has started. WSJT-X does try and avoid that but some rigs do not provide feedback that they have switched to SEND mode.

I would guess that the delayed PTT via CAT is something to do with your K9JM CI-V router. Have you tried eliminating that for a test, taking care to remove any sensitive/buggy devices from the CI-V bus, like a PW-1 PA.

73
Bill
G4WJS.

Morning Bill, thanks for the above.

Re: the audio clicks (or splats!) at the start and occasionally the end of a transmit period, I take your point about the PTT not being asserted (within the rig?) until after WSJT-X has started to generate and send the audio, but shouldn't the Tx delay setting in WSJT-X take care of that?  My understanding has always been that the Tx delay is between WSJT-X executing its command to enable PTT and the onset of the Tx audio generated by the s/ware, so increasing the Tx delay to say 0.5secs should give ample time for the rig to receive the PTT command via whatever option is selected and action the changeover from Rx to Tx before the audio arrives.  As I mentioned previously, increasing the Tx delay setting when I use the CAT PTT option doesn't seem to affect the presence of the audio splats, although I haven't tried using a delay setting of >0.5secs.

With regard to your second point, there's a slight misunderstanding - I experience the seemingly randomly-delayed start of transmission when I DON'T use the CAT PTT option, so the presence of the K9JM router in the CAT connection between PC and rig shouldn't have any bearing.  The rig's PTT is controlled entirely by the G4ZLP datamodes interface device which appears to WIndows as an external audio codec in the same way as a SignaLink-USB.  The PTT signal generated by a VOX-type circuit within the G4ZLP device is hard-wired to the rig's PTT input on the ACC1 socket, so as soon as the audio generated by WSJT-X begins to emerge as an analogue signal from the codec within the G4ZLP device the VOX circuit should toggle the PTT line - apparently the 'VOX delay' is only of the order of 10-20msecs.

73
--
Martin G0HDB

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