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Re: Unable to decode QtSoundModem Beta v0.0.0.62 1200 baud AFSK


 

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Extra decoders are set in the Modem config tab in the Add Rx n pairs box.

These are not needed on FM. On SSB tuning has to be within about 30Hz for packets to decode successfully. This amounts to a TX to RX accuracy of around 2 parts per million on 20 Meters. Modern rigs are usually that stable, but do not always have that accuracy. So QtSM can add extra decoders tuned +- 30 Hz from the nominal. I find two pairs (a total of 5 decodes) is usually enough for normal HF operation. Each extra pair adds to the cpu load so if you are running several modems on a relatively slow platform like a Pi 3 you may need to check that you aren't overloading the cpu.

QtSM reports the success of each decode in the form [--+++]. This shows that the top 3 decodes were successful, suggesting the station was around 30 Hz high. If all stations appear either low or high it may mean you are a bit off frequency. If you see stations that are always? on the edge (eg [----+] than maybe you need more decodes (or to persuade the other station to move a bit!)

73,
John



On 18/05/2023 23:28, Matthew 2E0SIP wrote:

Hi Red,

Thanks for the debugging tips.

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Make sure you¡¯re only running 1 extra pair of decoders per port on QtSoundModem if running on SSB

I'm not sure where this is configured? I've not enabled any.

Make sure IL2P isn¡¯t enabled as well as FX25 on a single port.

IL2P is disabled on both sides (QTSM and the NinoTNC)

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Try fiddling with the extending the TXDelay in normal AX25 mode.

I set it to 500ms to rule out any issues and it didn't help.?

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I've attached the WAVs. Both are the string "Hello" sent 3 times.

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Thanks

Matthew

2E0SIP

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