WSPR Transmitter

It was an interesting week. I had my 11yo son put together my second prototype WSPR transmitter. Watching someone build this was both instructive and rewarding. I saw first hand how important it was for consistency in labelling parts on the circuit diagram and parts placement diagram.  And rewarding to see that one of your creations can be replicated.

I lost a lot of time testing the synthesiser though. It took me several attempts before I realised the reason the phase lock loop (PLL) was not locking up was not related to the loop filter which I thought was the issue. Instead, it was the oscillator was too low level for the PLL counters to work properly all the time.

As the frequency changed the oscillator level also changed. And it turns out the levels were right on the limit for reliable counting. So it would appear to be working properly when the frequency into the PLL was too low, but as the frequency increased it started counting in error so the error signal into the loop filter was still saying the oscillator was too low.

All is good now though. After some more testing I should be in a position to release further details shortly.

73's
Richard