Sunday 22 November 2020

Locking the Adalm Pluto to an external reference (Part 2)

 Having worked out how to inject the external reference the next question was what frequency to inject. Should I use 40MHz like the original?  Looking in my junk box I found a G4HUP DFC30 unit which takes a 10MHz reference and provides a 30MHz output. I tried retuning the output filter to 40MHz but the multiplier was very ineficent at times 4. So i tried retuning the output filter to 50MHz which worked fine. The reference was to be 50MHz

In my parts collection I found a 10MHz oscillator which could be used to drive the multiplier when no external reference was available. It also had a relay to switch between internal and external reference.

The 10MHz oscillator and DFS30 as deployed in the Langstone:-

That is the hardware done, next to get the 50MHz reference in the software!

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