TB7100 RB-STM32-DVM Troubles

The TROUBLE is that the RB-STM32-DVM refuses to decode the RX Audio form the TB7100 repeater. Why?

What can affect the RX Decoding of the DVM?



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Audio Signal Properties

The audio signal to decode is:

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Timeline of tests

  1. 2020-01-31 - Analyse mmdvmcal results
  2. 2020-01-31 - run more mmdvm cal tests
  3. 2020-02-02 - Understand SAM ADC conversion on RX chain.
  4. What should I see on TP1, TP2, TP3
  5. Look at specs of MCP6002


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mmdvmcal Results



select w to turn on debug messages
Setect b to place the DVM in BER receive Mode
PPT on the hand held to transmit into the repeater



Note

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csbk - Controll Signaling Block

If its derives, check to TCXO output with a scope. The sinus level must be 0-3.3V. If the 0 is not reach (highest value), you may shorcut C22.



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Source: https://github.com/g4klx/MMDVM/wiki/MMDVM-Calibration

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G4KLX Wiki Notes

https://github.com/g4klx/MMDVM/wiki

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MMDVM Specification

https://github.com/pd0mz/go-dmr/blob/master/docs/MMDVM%20Specification%2020151208.pdf

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DMR Audio RX Images

RX Audio at 0.000mS:
RX-time.000.png

RX Audio at 0.033mS:
RX-time.033.png

RX Audio at 0.064mS:
RX-time.064.png

RX Audio at 0.100mS:
RX-time.100.png

RX Audio at 0.131mS:
RX-time.131.png


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SK2HG - Kalix Radio Club

Kalix Radioklubb C/O Sture Bylund Kajvägen 5 952 95 BÅTSKÄRSNÄS Sweden Page managed by SM2OAN

SK2HG - Tait TB7100 as DMR repeater:
http://www.sk2hg.se/wp/?page_id=3246

Adjusting the RX settings was much more diffcult, I did not found any info about how the MMDVM.ini file should look like for TB7100. The TB7100 has DSPs in both the TX and RX path so the signals are delayed. This was no problem with my first DMR project, the GM-340 based Repeater.

Before struggeling with the RX path I decide to open the Squelch as the Audio output was squelched. It had to be done with the Tait calibration program (TB71_CAL) not with the normal CPS program (TB71_XPA), by setting a low value for squelch opening, I think I put -136 dBm there. After a lot of trying I found the settings below to work. I have used them for both repeaters with very good result.

sk2hg-DMR-Settings.png

K2IE - MMDVMCal - Duplex Hotspot Reliability Revisited:
https://www.k2ie.net/blog/tag/mmdvmcal/ K9NPX - Hotspot Offset Calibration - February 05, 2019:
http://www.k9npx.com/2019/02/hotspot-offset-calibration.html

http://ks-dmr.net/2019/06/14/configuring-mmdvm-for-the-mtr2000-and-stm32-dvm-mtr2k/ https://pd0zry.nl/posts/motorola-mtr2000-dmr-repeater/

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Glenn Lyons VK4PK
glenn@LyonsComputer.com.au
Ver:gnl20220201 - pre published v0.9