How can I figure out why sdrtrunk is re-tuning the receiver?

[Erik Swan]

I am using an SDRPlay RSPdx with my local statewide P25 system. The site I have setup in SDR trunk (RR link) should be able to fit entirely within the bandwidth of my RSPdx (configured for 8 Msps).

However, when I'm watching the waterfall view, I'm noticing that occasionally sdrtrunk is re-tuning the receiver to shift the sampling window. As far as I can tell there is no reason for this as the control channel and all of the traffic channels fit inside the entire window. Sometimes the shift is small, other times it is large.

Is there a log setting I can enable or some reason to get sdrtrunk to tell me why it is re-tuning the receiver?

I've looked in the application log but I do not see any messages about when and why the tuner(s) are re-tuned.

[Nate]

See how this guys channel has two NBFM channels that are just idling?

https://www.youtube.com/watch?v=BtmGgdRcNjY&ab_channel=CitizenJoe 

These hold the upper ends of the tuner in place.

Otherwise it moves around as the window averages the channels that are tunned in.

I do the same thing also but that guys channel has it in view.

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[Erik Swan]

Thanks, that's a helpful workaround.

It's very odd to me that sdrtrunk is re-tuning the receiver just to keep the center of the window at the "average" of the tuned channels. Mayber there is a good reason for it but in my mind it shouldn't re-tune unless it discovers that it's absolutely necessary because of a channel grant outside of the current tuning range/window.

There is a cost to re-tuning the receiver - it doesn't happen instantly and it's probable that some data will be missed until the SDR is locked on the new center frequency.

Has this been discussed before/elsewhere?

[cha...@lindseyfamily.net]

There are several open issues for this request. Here is the original request put in by Deny and was not too long ago marked as a milestone for the next few releases.  https://github.com/DSheirer/sdrtrunk/issues/172

1277, 1002, and 904 also related.