Simultaneous transmission on both time slots.

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

Re: Simultaneous transmission on both time slots.

Post by G4EML » Mon Dec 30, 2019 6:22 pm

Roger,

I may have found a possible reason for the reported problem with apparent transmission on both timeslots.
While testing with the scope I happened by accident to capture the end of the transmission from the GD77. The last frame appeared to be 90ms long!

I then did a few more captures specifically looking at the end of transmission and can confirm that right at the end of the transmission the radio is sending on both timeslots just for one frame. If this is the 'Call Terminate with LC' and this is being sent on both timeslots then it might explain the strange things Fabio has been observing. Brandmeister may be receiving a terminate message on both timeslots and assuming the call has been using both, when in fact the rest of the call was correctly on just the one timeslot.

All the remainder of the transmission is correctly timed.

End of transmission from GD77. Note the last frame is occupying both timeslots.
Last Frame Error.png
Last Frame Error.png (12.15 KiB) Viewed 4575 times

Same thing with both timeslots in use. Note the interference during the last frame caused by both radios transmitting at the same timeslot.
Timeslot clash.png
Timeslot clash.png (14.08 KiB) Viewed 4575 times

I have not had time yet to work out what is causing this but it should be possible to fix it.

(It does the same in both versions of the firmware, with or without Rx in the unused slot, so that has nothing to do with it)


Colin G4EML

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

Re: Simultaneous transmission on both time slots.

Post by G4EML » Mon Dec 30, 2019 9:41 pm

I may have found the bug.

Fabio, please can you give this version a try. It fixes the problem I found, I hope it also fixes your problem.

[The extension sgl has been deactivated and can no longer be displayed.]

Roger, I have PR'd the fix to my Github. If it works I will raise a PR for you.


Colin.

VK3KYY
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Location: Melbourne, Australia

Re: Simultaneous transmission on both time slots.

Post by VK3KYY » Mon Dec 30, 2019 9:50 pm

Thanks Colin

Does this change fix the dropout if Rx is enabled , or just the double frame transmission?

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

Re: Simultaneous transmission on both time slots.

Post by G4EML » Mon Dec 30, 2019 9:53 pm

No, dropout if Rx enabled is a different problem. I didn't continue with that..
This only fixes the timeslot clash at the end of a transmission.

VK3KYY
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Location: Melbourne, Australia

Re: Simultaneous transmission on both time slots.

Post by VK3KYY » Mon Dec 30, 2019 10:08 pm

Ok.

I will see if I can find out why the audio gets dropouts if Rx is enabled

VK3KYY
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Re: Simultaneous transmission on both time slots.

Post by VK3KYY » Mon Dec 30, 2019 10:10 pm

Btw. Can you email me your fw_c-6000.c file so I can look at the other change

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

Re: Simultaneous transmission on both time slots.

Post by G4EML » Mon Dec 30, 2019 10:18 pm

Done.

VK3KYY
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Location: Melbourne, Australia

Re: Simultaneous transmission on both time slots.

Post by VK3KYY » Mon Dec 30, 2019 10:36 pm

Thanks

No need to do a PR. I can diff the file and copy the change across and get some more people to test it

IZ2EIB
Posts: 161
Joined: Sat Nov 30, 2019 12:55 pm

Re: Simultaneous transmission on both time slots.

Post by IZ2EIB » Mon Dec 30, 2019 11:30 pm

Hi Roger and Colin, thank you both for the difficult investigations you are carrying out to try to fix the problem!
VK3KYY wrote:
Sun Dec 29, 2019 10:27 pm
Guys

Can you try this version.

The radio is configured to Rx during the alternate TS, during Tx, i.e the PA will be turned off and the antenna switch will be changed and the Rx preamp will be enabled.

It has audio drop-out problems on Tx when I use it with a Motorola DR3000 repeaters, which is why I don't normally operate the firmware in this way, but it should definitely not be transmitting on both TS.
Thanks a lot Roger!
Sadly, though, from my side the problem is still there:
03149c7.png
03149c7.png (2.63 KiB) Viewed 4527 times
30122019_prima.jpg
30122019_prima.jpg (228.48 KiB) Viewed 4527 times
However, I do not notice any problems with the audio, but I plan to keep checking in this regard.
Thank you Roger!


@Colin

Thanks for the time you are spending checking directly on a real repeater!
I believe that what you are doing is very important as it allows to see things as they really are without having to rely on more or less valid hypotheses.
I am pretty sure that what you have managed to find and you will find will be important for the solution of the problem.
Thank you very much Colin!
G4EML wrote:
Mon Dec 30, 2019 9:41 pm
I may have found the bug.

Fabio, please can you give this version a try. It fixes the problem I found, I hope it also fixes your problem.

OpenGD77_201912302100-Fix-for-end-of-tx.sgl

Roger, I have PR'd the fix to my Github. If it works I will raise a PR for you.


Colin.
Thank you Colin!
I quickly tried the new firmware you sent and it would seem that it fixes the problem of simultaneous transmission on both time slots:
OpenGD77_201912302100-Fix-for-end-of-tx.sgl
30122019_dopo.jpg
30122019_dopo.jpg (290.26 KiB) Viewed 4527 times
(I can not insert a screenshot of the firmware OpenGD77_201912302100-Fix-for-end-of-tx.sgl as the forum does not allow me to insert more than 3 images, sorry)

Sadly though it introduces another oddity.
The transmission takes place on the correct time slot, but I can not listen to myself on the other GD-77 I have here on which is running the factory firmware from Radioddity.
In addition, the traffic that I clearly listen on the GD-77 where is running this experimental Open firmware with the GD-77 running the stock firmware from Radioddity I do not listen it even if the TG is the sameone, with this latter GD-77 I must enable the promiscuos mode in order to be able to listen to it.
In order to check this I invoked the TG91 from the GD-77 with the experimental Open firmware while listening to the same TG91 with the other GD-77 where is running the stock firmware from Radioddity and I saw that with the GD-77 with Open firmware I could listen to the ongoing QSO, but with the GD-77 with the factory firmware from Radioddity I could not listen to it, to do it I had to enable the promiscuos mode.
TG and time slot were the same for both GD-77s, either because I saw it on the BrandMesister dashboard, and because in the end I disconnected the TG91 invoking the TG4000 from the GD-77 with the factory firmware from Radioddity and the communication has stopped as it was logical to expect.
Another thing that I noticed is that instead by transmitting via repeater with the GD-77 where the factory firmware from Radioddity runs, the other GD-77 where the experimental Open firmware is running is able to listen to the communication, as opposed to what happens with inverted parts as I have just described here above, because in that scenario I had to enable promiscuous mode (but in the Open firmware the promiscuos mode is always enabled...).
I hope I managed to explain myself.
Thanks!

73 best regards de Fabio IZ2EIB

VK3KYY
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Location: Melbourne, Australia

Re: Simultaneous transmission on both time slots.

Post by VK3KYY » Mon Dec 30, 2019 11:53 pm

Colin has definitely found a bug, so I am including a change to fix that bug.

However, I'm sure we still have at least one other bug in the DRM system.

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