Auto-Calibrate ppm correction

[K1LSB]

Wondering how difficult it would be to incorporate something similar to how HDSDR does it:

Thank you in advance,

Mark

[Simon G4ELI]

Not difficult but possibly pointless unless the SDR is locked to a good reference?

[K1LSB]

Simon,

Yes, of course, the VFO must be locked to a reference signal. That screenshot was intended to capture the implementation of the feature, and I had inadvertently already tuned away from the reference frequency when the screenshot was taken. However, the pic does show the date, time and frequency when the last calibration was done.

Thanks,
Mark

[Simon G4ELI]

Simon,

Yes, of course, the VFO must be locked to a reference signal. That screenshot was intended to capture the implementation of the feature, and I had inadvertently already tuned away from the reference frequency when the screenshot was taken. However, the pic does show the date, time and frequency when the last calibration was done.

Thanks,
Mark

OK,

But if the radio is locked then any offset can only be due to the PC clock being off I think.

[K1LSB]

Simon,

What I'm referring to is basically the ability to automatically adjust for any PPM error in the radio's displayed frequency, which currently must be done manually in your PPM Calibration window:

Mark

[Simon G4ELI]

I understand.

[jdow]

K1LSB, such a tool is really worthless if you have an oscillator that drifts as the correction must change automatically but you do not how how much or when. It is absolutely not needed if your oscillator is locked to GPS.

Furthermore if you lock to WWV, as an example, the time of day you do this is critical as well as the path length between you and Ft. Collins or Hawaii will change with time of day as the layers it bounces from change.

Yet more, if there is a converter present no matter how hard you try to lock to a precisely known frequency that is a transient calibration one frequency at best if the converter oscillator is not locked to GPS. You need to iteratively calibrate the oscillators using two precise frequencies.

I used HF to calibrate a standard back in the days before GPS. I got it to about 1 part in 10^8 comparing time drift with WWV over the better part of a year. After that I was simply correcting the oscillator crystal's aging drift.

{o.o}

[K1LSB]

JoAnne,

The tool is not "worthless" to me or anyone else who uses WWV to calibrate any significant error in frequency. I use the feature in HDSDR on a regular basis for all of my radios. It works plenty reliably enough that I can clearly observe the effect of thermal drift during warmup in several of my radios. Once the radios warm up the oscillator stabilizes well enough to use for awhile before needing recalibration.

So the feature is quite useful to me.

Mark