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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