SMT32 board & FSK error rate

Help with other MMDVM Repeater Boards (with NO onboard RF)
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KZ4FOX
Posts: 18
Joined: Fri Jun 28, 2019 6:58 pm

SMT32 board & FSK error rate

Post by KZ4FOX »

Hey Gents -

Going to do my best to try and relay this issue. So a buddy whom is an RF engineer connected up his digital service monitor so we could try and DMR adjusted for a repeater using the STM32. No matter what we seemed to try we couldn't get it into spec. The magintude was soild but FSK error rate was way to high. His monitor doesn't show the constellation well but never seems like we could get it full inline (hard to see but there are red "marks" there. Anyone spec-ed these out with a high end digital monitor before? As it stand, the unit does work but other than say Anytone's no other radios will work or hand shake (including commercial motos). Apologies if im not explain as well but attached is a screen cap doing the 1031 DMR test w/MMDVMcal.

Mark
KZ4FOX
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KZ4FOX
Posts: 18
Joined: Fri Jun 28, 2019 6:58 pm

Re: SMT32 board & FSK error rate

Post by KZ4FOX »

Yeah, this is connected to a TK-740 VHF repeater (on-site, it has a high power amp) but makes sense figured worth asking at least :) I know the bulk of users are using Pi-Star based HotSpots so my question is "out in the weeds" so to speak. DMR is just really picky being TDMA vs FDMA. The FDMA modes seem to be pretty easy to get going.
KZ4FOX
Posts: 18
Joined: Fri Jun 28, 2019 6:58 pm

Re: SMT32 board & FSK error rate

Post by KZ4FOX »

Yeah, I had a typo in my title. Its a repeater builder STM32 board for repeaters :)
KZ4FOX
Posts: 18
Joined: Fri Jun 28, 2019 6:58 pm

Re: SMT32 board & FSK error rate

Post by KZ4FOX »

I think I have found the answer! I keep forgetting on these Kenwood repeaters its used the serial/data line. Those values can and seem to often need to boosted to get the deviation to be set right:
Depending on the existing configuration of the repeater it may be necessary to adjust the TXD and RXD levels to ensure correct operation of the MMDVM, as these levels directly control the output receive signal levels to the MMDVM and the transmit deviation applied to signals from the MMDVM.

During build of 5 repeaters, we found that most of them required the levels to be increased close to maximum for best operation on ZUM 1.0 boards.

If you have attempted to adjust the MMDVM receive and transmit levels using the trim-pots on the MMDVM board but cannot get it working reliably or in a particular mode, you can adjust these levels by connecting to the repeater using the KPG-91D software and opening the “Test” mode found under the “Program” menu:-
So we will we bench that unit and try to retune. I'll post the results so can keep a record if someone else asks :)

Mark
KZ4FOX
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