Transmitting on VHF DMR Repeater not possible

Riku
Posts: 56
Joined: Sat Nov 16, 2019 8:59 am

Re: Transmitting on VHF DMR Repeater not possible

Post by Riku » Thu Dec 12, 2019 9:12 pm

i did tried 2 different hotspots.
also i tried stock firmware into one gd77, and that worked flawlessly, like 2017.
losting sync is happening only with opengd77 software.

Tested also with our uhf repeater, it is breaking there too, only the green light wont go off or callsign does not reappear. but it is breaking alot. compared to stock firmware it is totally different..
how come ppl dont notice this issue??

edit here is a video from our local repeater, Left side opengd77 with external outside antenna(to ensure good signal) and right side stock firmware.
Left side is breaking all time, right side coming without problem.
https://drive.google.com/file/d/1FwzliQ ... sp=sharing
Riku / OH1E
facebook fan group: https://facebook.com/groups/OpenGD77/

Riku
Posts: 56
Joined: Sat Nov 16, 2019 8:59 am

Re: Transmitting on VHF DMR Repeater not possible

Post by Riku » Thu Dec 12, 2019 9:30 pm

another update. using opengd77 as hotspot and other opengd77 as radio to work with it, it seems no sync problems. actually this is only way how i got it coming "crystal clear".

edit:i do have one more hotspot, its openspot but i havent used it for years :D i can try that too
Riku / OH1E
facebook fan group: https://facebook.com/groups/OpenGD77/

G4EML
Posts: 171
Joined: Sat Nov 16, 2019 10:01 am

Re: Transmitting on VHF DMR Repeater not possible

Post by G4EML » Thu Dec 12, 2019 9:51 pm

I have not heard the same problem with either my two radios on either UHF or VHF.
Just for reference what was the frequency of the repeater you were listening to?
It may be that there is some sort of bug in the frequency setting routines that only shows up on some frequencies.
If the radio was slightly off frequency I can see how that could cause what you are hearing.
I will do some testing to see if I can reproduce your problem.

Riku
Posts: 56
Joined: Sat Nov 16, 2019 8:59 am

Re: Transmitting on VHF DMR Repeater not possible

Post by Riku » Thu Dec 12, 2019 10:04 pm

repeater is on 434.5625 -2Mhz
hotspot1 144.9625
hotspot2 434.450
gd77hotspot 434.450

only thing is my codeplug then if no one can reproduce this. ? but it is hard to belive this
how come radio is off frequency if stock firmware works
Riku / OH1E
facebook fan group: https://facebook.com/groups/OpenGD77/

G4EML
Posts: 171
Joined: Sat Nov 16, 2019 10:01 am

Re: Transmitting on VHF DMR Repeater not possible

Post by G4EML » Fri Dec 13, 2019 12:01 am

The frequency calibration is carried out by the firmware. The values used should be the same as the official firmware uses. If there was a problem it could be setting the radio to the wrong frequency.
However I have just tested my radio on an RF test set and it appears to be OK.
The only way I could reproduce a similar problem to yours was to offset the frequency by 1.5KHz.
It’s midnight here now so I will do some more testing tomorrow.

If you have time it might be worth changing your receive frequency by plus and minus 1 KHz and see if either makes any difference. You can do that by transferring the memory to the VFO and then adjusting the frequency.

Riku
Posts: 56
Joined: Sat Nov 16, 2019 8:59 am

Re: Transmitting on VHF DMR Repeater not possible

Post by Riku » Fri Dec 13, 2019 8:46 am

Changing frequency indeed helped on problem.
i tried on UHF repeater i needed like +1khz offset until it was better.
on vhf was like -0.2khz big difference.
also it depends radio, other radio does alot less than other.

my gd77 are from latest batch and other is from first batches back years ago when it was released, it is odd because no one else has these issues and i do have with both radios with this problem only with opengd77.

So is there any way to get this calibrated right, chip has some base freq output what can be read with cpu to self calibrate? i know i could open radio and hook up measurement devices if i can find IF points etc and look that way, but well somehow it is working with stock firmware, so there must be something to get references in software.?
Riku / OH1E
facebook fan group: https://facebook.com/groups/OpenGD77/

G4EML
Posts: 171
Joined: Sat Nov 16, 2019 10:01 am

Re: Transmitting on VHF DMR Repeater not possible

Post by G4EML » Fri Dec 13, 2019 10:42 am

That’s interesting,

I don’t know why it appears different between the stock firmware and open GD77. In theory they should be the same. But we are working a little bit blind with OpenGD77 because the datasheets for the chips involved are very poor with a lot of information missing or unclear. It could be that we have missed an important setting somewhere.

It is a little odd that you found UHF and VHF to need adjustment in opposite directions. If the master calibration was incorrect I would have expected the error to be in the same direction.

It is also strange that you are seeing this and others are not. I can’t explain that yet.

There is no easy way for the radio to self calibrate. It needs an external frequency measurement on a frequency counter.

I will do some more experimenting later.

Riku
Posts: 56
Joined: Sat Nov 16, 2019 8:59 am

Re: Transmitting on VHF DMR Repeater not possible

Post by Riku » Fri Dec 13, 2019 12:42 pm

i did measuraments with cmu200 on tx only analog side and it is well inside channel frequency, tdma is abit other thing to measure, even the communicator tester has tdma feature, i was unable to able measure that one. best way is open radio and search IF points from different ocillator/mixers and see there :D :D but but
Riku / OH1E
facebook fan group: https://facebook.com/groups/OpenGD77/

G4EML
Posts: 171
Joined: Sat Nov 16, 2019 10:01 am

Re: Transmitting on VHF DMR Repeater not possible

Post by G4EML » Fri Dec 13, 2019 4:34 pm

I have just done some testing to compare the openGD77 firmware with the official firmware V 3.2.2

This was tested with my Marconi 2955 test set externally modulated with a DMR test signal generated by a modified MMDVM board. The test signal is a looped voice recording using MS syncs on CC1 TG9. Testing was done at 434.5625 and at 144.9625 at a signal level of -110 dBm.

I could not detect any difference in receive performance between the OpenGD77 firmware and the official firmware on either frequency.
The signal was received without errors or dropouts when on frequency and also when moved + or - 1Khz.
Dropouts began to be observed when the frequency was moved by + or - 1.5Khz.

The DMR specification states the frequency error must be less than +-2ppm which would equate to +- 880Hz at 440 MHz. So the radio appears to be easily capable of meeting this.

Based on these tests I think we can rule out a firmware frequency error as the cause of your dropouts. (Unless your radios are massively out of calibration which it doesn't sound like they are.)

At the moment I am not sure what else you can try.

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EA5SW
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Joined: Sat Nov 16, 2019 9:45 am
Location: Valencia, Spain
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Re: Transmitting on VHF DMR Repeater not possible

Post by EA5SW » Fri Dec 13, 2019 9:29 pm

The OLD Tier1 firmware (october) works OK with the Hotspots, the newer have sync errors.

Tested with 3 talkys and 3 hotpots, one is duplex
Jose - EA5SW - Valencia

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