Calibration

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AA3RP
Posts: 86
Joined: Thu Jun 17, 2021 3:22 am

Calibration

Post by AA3RP » Mon Jul 18, 2022 6:55 pm

Is there a desire / plan to have Calibration function in the CPS for the MD900 at some point ?

Also I have access to a good RF lab that has all the test equipment need to 'tune / calibrate' with. I have read that the fundamental frequency adjustment is physical adjustment on the main circuit board. Are there any photos / diagrams / videos showing and explaining this?

Finally will the option to save calibration data for the MD9600 be added to the CPS ?

Thank you to all that have made this firmware possible and greatly improved the usability and functionality of the MD9600 radios.

AA3RP

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: Calibration

Post by VK3KYY » Tue Jul 19, 2022 4:46 am

It would be nice to be able to include calibration for the MD9600 into the CPS, but the critical ingredient is that no one has any spare time to do that work.

G4EML
Posts: 919
Joined: Sat Nov 16, 2019 10:01 am

Re: Calibration

Post by G4EML » Tue Jul 19, 2022 8:26 pm

There is very little in the calibration that should ever require adjusting. The feature is really only used during manufacturing.
Hence there is not a lot of urgency to provide this feature. It will probably happen eventually, but not soon.

The only adjustment that may need to be made as the radio ages is the adjustment of the reference frequencies for the VHF and UHF synthesisers.
These can be adjusted individually using old fashioned preset pots. No software is needed for this!

Remove the top cover of the radio. You will see two small preset potentiometers on the edge of the board nearest the front panel. The one nearest the ribbon cable is for UHF, the one furthest from the ribbon cable is for VHF. These should be adjusted to give the correct transmit frequencies. The receive frequencies will then also be correct.


Colin G4EML

AA3RP
Posts: 86
Joined: Thu Jun 17, 2021 3:22 am

Re: Calibration

Post by AA3RP » Wed Jul 20, 2022 4:23 pm

G4EML wrote:
Tue Jul 19, 2022 8:26 pm
There is very little in the calibration that should ever require adjusting. The feature is really only used during manufacturing.
Hence there is not a lot of urgency to provide this feature. It will probably happen eventually, but not soon.

The only adjustment that may need to be made as the radio ages is the adjustment of the reference frequencies for the VHF and UHF synthesisers.
These can be adjusted individually using old fashioned preset pots. No software is needed for this!

Remove the top cover of the radio. You will see two small preset potentiometers on the edge of the board nearest the front panel. The one nearest the ribbon cable is for UHF, the one furthest from the ribbon cable is for VHF. These should be adjusted to give the correct transmit frequencies. The receive frequencies will then also be correct.


Colin G4EML
Thank you for the information. Last year I bought an 'open box / returned' MD9600 at a very discounted price. When I tried to use it, I was not able to use it on 2m band and what audio reports I got where not good. I asked to return the radio for another open box one, but was told they had no more so I was refunded the purchase. When I asked how to return it I was told by the vendor they would have no need of it and I could just keep it. So I ended up with it.

I brought it out again and loaded the OpenMD9600 firmware and did some more testing. 70cm repeaters seem to work fine and DMR works fine on all my local DMR repeaters, which are all in the 70cm band. Yet the 2m side does not seem good. The more I tested at my QTH the more it seems that the VHF may be off frequency. This is the motivation behind my post.

Thank you for the information on the tuning pots for UHF and VHF. I will arrange to get to the test lab that one of the members of my Radio Club has and offered to club members to utilize. Hopefully I will be able to restore this MD9600 to working order.

AA3RP

AA3RP
Posts: 86
Joined: Thu Jun 17, 2021 3:22 am

Re: Calibration

Post by AA3RP » Wed Jul 20, 2022 4:42 pm

G4EML wrote:
Tue Jul 19, 2022 8:26 pm
There is very little in the calibration that should ever require adjusting. The feature is really only used during manufacturing.
Hence there is not a lot of urgency to provide this feature. It will probably happen eventually, but not soon.

The only adjustment that may need to be made as the radio ages is the adjustment of the reference frequencies for the VHF and UHF synthesisers.
These can be adjusted individually using old fashioned preset pots. No software is needed for this!

Colin G4EML
Thank you and VK3KKY for the replies and the clear and honest response. I understand investing your time and effort in what has the 'best / most useful' result for the overall project.

As my previous post on this topic explains I look for purchasing deals on open box / returned / used MD9600 radios and having the ability to read and verify calibration would very handy for me. Yet I am not able to work on the coding of this firmware project directly. At most I can test / use and report back. The people who are able to directly work on and create this firmware have done amazing and great work in my opinion and continue to do so. I have no problem trusting in them and their judgement, and have the time to wait for calibration via CPS.

Thank you and all the developers for your work and efforts.

AA3RP

G4EML
Posts: 919
Joined: Sat Nov 16, 2019 10:01 am

Re: Calibration

Post by G4EML » Wed Jul 20, 2022 11:32 pm

Many of the early MD9600s have problems with VHF DMR when running at less than full power.
Unfortunately it is a design fault and not easily rectified. The only solution is to always run VHF at full power.

Later models had significantly modified PA stages and power control circuitry to fix the problem.

Colin.

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: Calibration

Post by VK3KYY » Wed Jul 20, 2022 11:52 pm

Initially I tried making some changes to the PA drive to resolve the problem, but the beta tester who thought he had the PA problem later reported that his radio seemed now to be working OK, however I think he is probably only using UHF.

Possibly pulsing the PA drive to its max level for the first few milliseconds of the transmission on VHF would allow the radio to operate at lower average powers on on VHF.

But this would depend on whether VHF works when the radio is set to high power

AA3RP
Posts: 86
Joined: Thu Jun 17, 2021 3:22 am

Re: Calibration

Post by AA3RP » Thu Jul 21, 2022 2:20 am

VK3KYY wrote:
Wed Jul 20, 2022 11:52 pm
Initially I tried making some changes to the PA drive to resolve the problem, but the beta tester who thought he had the PA problem later reported that his radio seemed now to be working OK, however I think he is probably only using UHF.

Possibly pulsing the PA drive to its max level for the first few milliseconds of the transmission on VHF would allow the radio to operate at lower average powers on on VHF.

But this would depend on whether VHF works when the radio is set to high power
Thank you for the reply and additional information / insight about early PA issue for VHF. I will do some more testing. It will be a while as I have to make a trip that will have me away for apx 3 weeks. When I am able to test again I will report back. This radio is a V2.1 hardware.

AA3RP
Last edited by AA3RP on Thu Jul 21, 2022 2:23 am, edited 1 time in total.

VK3KYY
Posts: 7478
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: Calibration

Post by VK3KYY » Thu Jul 21, 2022 2:23 am

AA3RP wrote:
Thu Jul 21, 2022 2:20 am
Thank you for the reply and additional information / insight about early PA issue for VHF. I will do some more testing. It will be a while as I have to make a trip that will have me away for apx 3 weeks. When I am able to test again I will report back.

AA3RP
OK. Let us know if using high power fixes the problem, and if so we may be able to send you a 'test' version which modulates the PA drive as a workaround.

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