It's all about the Software

Thanks Simon. Yes, the 40MHz is always present and is so before the Pluto is plugged in.
The observation is reproducible. Attached logfile of the sequence. Charlie

I have just modified my Pluto for external (40MHz) reference, taking care to get the level correct. All seems to be working fine, apart from a frequency offset that I (eventually) cleared by setting the offset to zero (it had a stored value, presumably what was correct for the on-board reference osc...

Thanks, found it with your link

Really dumb question, sorry!
Please can you tell me how and where on this forum to post a question about Adalm Pluto?