jks

About the "Custom band" fields:

SNR measurement uses the waterfall, although it's easier if you visualize it as using the spectrum. All those spectrum "bins", which originally start in frequency order, are re-sorted by signal strength. Then the 50% bin is taken as the noise floor. The 95% bin is taken as the highest level signal (the remaining 5% ignored to remove super strong outliers). The difference is the SNR. An approximation for sure. But that's what we have.

Now when you measure a custom sub-band you need it to occupy a large part of the spectrum so lots of bins are visible and available for the SNR computation. Just as you would if you were trying to view it in the user interface. And that requires a zoom level appropriate to the start/stop sub-band frequencies you want to use. If you left the zoom at zero (0-30 MHz), and you wanted to measure the 30m ham band, you'd only have a few bins available that covered that frequency range. Not much for the SNR computation to work with.

So, to figure out the correct zoom level to enter do this: With a regular Kiwi connection enter the center frequency of your custom band as the current frequency. Zoom all the way in. Now zoom out one step at a time until both the lo and hi values of your custom band just fit in the waterfall/spectrum. Use the zoom value "n" from the WFn button on the user control panel.

Results from custom band measurements, as well as from the "Also measure ham bands and AM BCB" checkbox setting, are only available from the URL query: my_kiwi:8073/snr (adjust actual Kiwi name/port as necessary). They are not currently displayed in any Kiwi admin or user web interface.

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Your image happens to fit the definition of a relatively large SNR value due to so many high valued bins plus many bins that are very low valued at the higher frequencies (very bad VDSL RFI in that image). Even though there are practically no useful signals outside of the AM BCB. That's just the limitation of the SNR algorithm.

I don't know anything about C#

Have a look at kiwiclient / kiwirecorder, written in Python. It does everything you need: https://github.com/jks-prv/kiwiclient

If you turn off audio compression you won't have to deal with the PCM coding.

In the next release I'll add a "custom" entry in the SNR measurement interval menu with a corresponding time field where you can enter the number of minutes you want.

I think I can also add a checkbox that asks for each ham band to get a separate measurement in addition to the 0-30 and 1.8-30 MHz measurements.

I've found the problem. I'm trying to get a release together as soon as I can. But it's much more difficult these days.

I’ll bet this happens if there’s a delay determining the local IP. Although I don’t know why that would be. That should occur almost immediately. I’ll take a look.