UHF Frequency problem.
Posted: Thu Aug 11, 2022 3:50 am
Apologies for the long email, but I wanted to capure all relevant information in the hope that it may help, I am having an issue with the UHF frequency on my MD-9600 I recently flashed withOpenGD77 frmware.
I have had the radio for a couple of years running the standard TYT firmware and have had no issue using it in DMR with my MMDVM hotspot.
I found out recently about the GD77 firmware, and was keen to give it a go, firstly congratulations on a superb improvement over the TYT firmware, it is awesome, well done.
Now the small problem I have...... I could not get it to work with my UHF mmdvm hotspot at all, i've set up numerous hotspots / different versions of DMR radio in the past so I am reasonably experienced, after spending a few hours on it, I think I have found the reason why.
Before I updated the firmware, I checked that the radio was exactly on frequency as I had read that tuner adjustments are not currently possible using the GD77 firmware, I checked the radio TX frequency using a HP 53131 counter with external GPS locked reference, both on the A band and B band at VHF and UHF, adjusting using the TYT CPS tuning where necessary to get it correct, hotspots are really critcal with regard to frequency and deviation.
After flashing the GD77 firmware though, the UHF frequency is low by 550 Hz, the VHF is exactly correct.
For analog, 550Hz is not really much of an issue but for DMR, the hotspot will not decode it at all, I then adjusted the hotspot frequency by 550Hz and the radio now works fine through the hotspot, but the hotspot now only works using this radio, not my Motorola / Anytone.
The radio is a version 2 hardware, and I am using the latest OpenGD77 firmware form the page that details the installation instructions (menu says Open MD9600 built 15:45:57 Jun 11 2022 cc117fc D)
These are the frequencies I programmed into the radio with the programming software and what the frequency counter said they were.
144.00000 transmits at 145.00000
146.00000 transmits at 146.000000
430.00000 transmits at 429.99945
440.00000 transmits at 439.99945
It doesn't matter if the UHF frequencies are programmed through the software into a memory channel as I did above, or entered via the radio keypad in VFO mode, the offset is always 550Hz low on UHF, so it would appear that it is firmware in the radio rather than the programming software.
I then reverted the firmware back to stock (TYT version MD9600-CSV-GPS-P06.24.bin), the frequencies on UHF are now exactly correct, so 430.00000 transmits on 430.00000 and 440.00000 transmits on 440.00000.
Flashing the OpenGD77 firmware again, the UHF frequencies are low by 550Hz again.
Appreciate the GD77 firmware is still in development, is it possible that some way of adjusting the reference frequency in the radio, like there is for battery cal and temp cal through the menu,or in the programming software could be implemented, or have I possibly found a 'bug' in the firmware when setting the PLL for UHF frequencies?
Any help with this is much appreciated, I have access to high grade calibrated test equipment should it be required to pinpoint the cause, and do any testing required to get UHF back on frequency.
Regards
Tony G1HMO
I have had the radio for a couple of years running the standard TYT firmware and have had no issue using it in DMR with my MMDVM hotspot.
I found out recently about the GD77 firmware, and was keen to give it a go, firstly congratulations on a superb improvement over the TYT firmware, it is awesome, well done.
Now the small problem I have...... I could not get it to work with my UHF mmdvm hotspot at all, i've set up numerous hotspots / different versions of DMR radio in the past so I am reasonably experienced, after spending a few hours on it, I think I have found the reason why.
Before I updated the firmware, I checked that the radio was exactly on frequency as I had read that tuner adjustments are not currently possible using the GD77 firmware, I checked the radio TX frequency using a HP 53131 counter with external GPS locked reference, both on the A band and B band at VHF and UHF, adjusting using the TYT CPS tuning where necessary to get it correct, hotspots are really critcal with regard to frequency and deviation.
After flashing the GD77 firmware though, the UHF frequency is low by 550 Hz, the VHF is exactly correct.
For analog, 550Hz is not really much of an issue but for DMR, the hotspot will not decode it at all, I then adjusted the hotspot frequency by 550Hz and the radio now works fine through the hotspot, but the hotspot now only works using this radio, not my Motorola / Anytone.
The radio is a version 2 hardware, and I am using the latest OpenGD77 firmware form the page that details the installation instructions (menu says Open MD9600 built 15:45:57 Jun 11 2022 cc117fc D)
These are the frequencies I programmed into the radio with the programming software and what the frequency counter said they were.
144.00000 transmits at 145.00000
146.00000 transmits at 146.000000
430.00000 transmits at 429.99945
440.00000 transmits at 439.99945
It doesn't matter if the UHF frequencies are programmed through the software into a memory channel as I did above, or entered via the radio keypad in VFO mode, the offset is always 550Hz low on UHF, so it would appear that it is firmware in the radio rather than the programming software.
I then reverted the firmware back to stock (TYT version MD9600-CSV-GPS-P06.24.bin), the frequencies on UHF are now exactly correct, so 430.00000 transmits on 430.00000 and 440.00000 transmits on 440.00000.
Flashing the OpenGD77 firmware again, the UHF frequencies are low by 550Hz again.
Appreciate the GD77 firmware is still in development, is it possible that some way of adjusting the reference frequency in the radio, like there is for battery cal and temp cal through the menu,or in the programming software could be implemented, or have I possibly found a 'bug' in the firmware when setting the PLL for UHF frequencies?
Any help with this is much appreciated, I have access to high grade calibrated test equipment should it be required to pinpoint the cause, and do any testing required to get UHF back on frequency.
Regards
Tony G1HMO