Re: Simultaneous transmission on both time slots.
Posted: 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.
Same thing with both timeslots in use. Note the interference during the last frame caused by both radios transmitting at the same timeslot.
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
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.
Same thing with both timeslots in use. Note the interference during the last frame caused by both radios transmitting at the same timeslot.
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