Repeater maintenance adventures at VK2RAG
Earlier this month our repeater team observed some anomalies with the MMDVM based repeater
Our team suspected there was something going on with the Arduino powered repeater control module.
Lindsay VK2AMV and Brad VK2NMZ took a field trip to the repeater site (and ensured they maintained 200mhz apart).
First thing was to check the configuration and firmware of the MMDVM currently in service.
We were unable to see anything that stood out so proceeded with further testing.
Next, we pulled out the Spectrum analyser to check output of the transmit amplifier.
With few dB of attenuation, we observed the output of the repeater was Clean. Like. Very clean.
The duo were most suitably impressed with this and proceeded to give the repeater a few pats. (remember to give your repeaters some pats every now and then – they do a good job!)
The next steps were to install the new Raspberry Pi and Repeater builder control board and bring this online.
Success! Now it is time for some further tuning of the audio deviation!
Using the spectrum analyser we performed tuning utilising the Bessel Null as the key tuning method.
For those who may be unaware, The BESSEL NULL FM deviation measurement is an extremely accurate way to obtain a precise deviation setting on any FM modulator operating at any RF frequency.
With some further fine tuning the team observed an uplift in stability and audio quality from Brandmeister DMR and D-Star services currently active on this repeater.
Kudos to the CCARC Repeater committee for keeping this site maintained and running!
-CCARC
