OpenGD77 DTMF deviation and speaker volume

posted in: DMR, GD-77, Ham radio | 9

There are currently some problems with the DTMF and 1750Hz Tone deviation, and the DTMF and tone audible feedback through the speaker is too loud

Ray VK3YNV emailed me to say that the DTMF deviation seems to be too high and is causing distortion.

The problem seems to be that the DTMF and Tone require a different master deviation setting to the normal FM audio.

The calibration data contains deviation settings for both of these but we did not use the settings in the OpenGD77 as the DTMF and 1750 tones sounded OK and seemed to work OK.

Anyway, Alex DL4LEX and I are aware of this problem and I think Alex is working on a solution.

With the audible feedback for the 1750Hz tone and the DTMF tones, I think the tones may be louder because the deviation is currently too high.

If after the deviation is reduced the audible feedback is still too loud it would be possible to reduce the overall audio gain on the AT1846S RF chip while the tones are being played.

I have not used either DTMF or 1750Hz in the official firmware, but I think possibly the audible feedback is too loud even on the official firmware, so I could either have a fixed amount of audio reduction when the tone is being played, or perhaps have a setting in the Options menu to control this. However because I don’t think this is something which is a big problem, adding a setting for this is probably overkill

9 Responses

  1. ken, M1DYP


  2. John P McDonald G8PJC

    GD-77 sending SMS via pi-start. Is it possible for a feature to be enabled to reduce the length of the preamble from a GD-77
    Pi-star/MMDVM is not able to support a long preamble.

  3. Jack

    Request: would it be possible to send to the serial output a set of text strings with informations like:
    TIME, FREQ, RSSI, BER, TS, TG, received CALL
    With a Putty connection it would be very interesting for diagnostic on repeaters (may be displayed on your modified software).
    Thanks for your precious work.

  4. EvO

    Hi Roger, thanks for the terrific work!
    At the moment I’m still using the Radioddity firmware with your excellent CPS Community and I’m very satisfied.
    But I follow the evolution of the firmware you’re doing and I would like to move on to that.
    Only one question and one request, if possible.

    Question: does your firmware solve the problem with the Admit Criteria or is it still necessary to set it as ‘Always’ in the GD-77?

    Request: would it be possible to add the possibility of decoding DMR communications regardless of Time Slot and Color Code possibly showing those two parameters so that it is possible to understand what they are?
    I guess that this is rather hard to obtain, but it would be of great help in the case of repeaters that due to interference with other neighboring areas are set with unusual color codes to try to limit interference, a bit like the use of different CTCSS tones.
    The possibility of being able to do so would also facilitate the setting of a repeater on the fly.

    Thank you so much again for your great work Roger, please keep it up!

  5. Janusz - SO5AJG

    Hi Roger,
    There is still a tremor of sound at random intervals, more often, sometimes very rarely. Interruption of this effect is only possible after switching the radio off and then on. Turning off calibration did nothing.

  6. Roger Clark

    Switching to FM and back to DMR will also fix this.

    The official firmware has the same problem but it happens less often. With the official firmware, you have to change channels to fix the problem

    I think the problem is missing DMR frames, and audio buffer under-run.

    I will need to add it to the bug list, but it doesn’t happen very often to me, which makes the problem hard to fix.

  7. Janusz

    I have the impression that these sound tremors occur much more often when I listen to correspondents from the DMR + network than from the Brandmeister network. I still need to watch these communications for a while.

  8. Janusz

    Sometimes I noticed that on DMR + there are fades even signal fades and the green LED on the radio goes off. Please be advised that while listening to the same transmission on AnyTone 878 is working correctly. The signal is obtained from the same source, i.e. the hotspot.

  9. Roger Clark

    This seems to be a common problem.

    It seems to be caused by calibration differences.

    However I don’t know why the OpenGD77 seems to need more accurate calibration than the official firmware etc

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