Wednesday, January 1, 2025

NEW - Southern Cape MMDVM Amateur Radio Digital Repeater on Test Bench (Part 1)

 

In June 2023 I picked up a Homebrew MMDVM / DMR Digital Repeater from one of the Swop Shop's in South Africa.  This repeater was lying dormant in my Shack since 2023 and I decided to scrutinize it on the work bench a few days before Christmas, set it up and get it ready for installation and use in Mossel Bay. 

First things first. Before switching on any acquired addition to the Shack I always open up the item to ensure that every part is still where it should be.  NEVER switch on anything as I have found that a parcel can be roughly handled by some courier services and parts might shake loose in the process.  Another reason for opening up the repeater is to clean the 3 cooling fans and any possible dust inside the cabinet.  No it did not come loose during transit but when I removed the back panel the double side tape totally gave way.

Herewith a few images of the inside of the repeater and the partly detached PCB I found inside the cabinet: (Click on images for larger view.)


 


Herewith a few images of the "inner workings" of the digital repeater:  (Click on images for larger view.)




After cleaning up the cabinet and fans, I installed the now loose fan controller board inside the cabinet away from the back plate and installed the clean fans back into place.  A final check revealed that it was time to close up the cabinet, plug in all the cables and switch the repeater on. It came to life but I needed to change a few settings in Pi-Star and Brandmeister before it worked as a DMR Repeater.

Herewith a few images of the display screen: (Click on images for larger view.)




Using my old trusty TYT MD380 HT I transmitted to the repeater and it seemed to work as it should.  However I needed to do a test with another DMR station.  Curtis ZS6CMO obliged and we had a short conversation via the repeater.  Curtis indicated that the audio quality was good and that there were no other audible issues present.  I would like to thank Curtis for the on the air test.  However further tests will be conducted including checking the alignment of the notch filter cavities (duplexer) just to ensure that it is on specification.



 
Video reflecting audio quality:


Herewith a few images of provisional testing and setup of the repeater:  (Click on images for larger view.) 




Future Upgrades and Setup:

How will this repeater be utilized?  The current plans are to first finish all upgrades and final setup of the unit.  Find or construct a 4 stack 70 cm antenna.  Once all the hardware and software "talks in harmony" I will release all necessary information about the digital repeater to fellow radio amateurs.  The digital repeater will be connected to the ZS-Link Network in Mossel Bay and will form part of the current network.  I will soon do further adjustments and testing on this repeater which will be listed in Part 2.


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