SNR value

G8JNJG8JNJ
in Configuration and Operation

Hi John,

I was trying to make some quick comparisons of the KiWi SNR values, whilst adjusting some filters.

I clicked the Measure SNR now button in the admin control panel, but it didn't seem to update the values shown at the top of the user GUI, although it does update the URL/snr page.

Would it be possible to display the updated SNR values next to the Measure SNR now button ?

Not rush, just a nice to have at some point, as it will save having to juggle and update multiple browser screens in order to obtain the current values.

Regards,

Martin

Comments

  • bensonbenson
    edited January 22

    Hi Martin,

    What is the frequency range you want to find the SNR estimate over when doing those adjustments?

    Last year worked on a Python script that creates a time plot of the SNR calculated by the microkiwi_waterfall code and runs that periodically every few seconds. This results in a plot as shown below, which was made today with usual poor propagation around noon.

    B_test_twin.png


    There are issues with this SNR estimate as mentioned in the forum a few times previously and I made some attempts to apply computer vision techniques to get an alternate measure of SNR from snapshots of Kiwi waterfalls without much succes. It turns out surprisingly difficult to express what the eye perceives as 'good quality' waterfall images in properties that can be measured reliably.

    If interested let me know by pm. The Python code is rough but functional and I have used it to see how powersupply filtering, bandpass filters or different antennas affect these 'wide band' SNR measures.

    Narrow band SNR (within the selected audio bandwidth) is another story and I hope one day that can be shown on the Kiwi S-meter extension plot as well

    Best regards,

    Ben

  • G8JNJG8JNJ

    Hi Ben,

    Yes, I'd like to have a look at that if possible.

    I've currently got problems with my VHF/UHF OpenWebRX sdr's at the Wessex site.

    The signal levels are fading up and down at random intervals, and I'm trying to figure out the likely cause. I don't know if this is due to changes in propagation or a faulty antenna. But I'd like to know before committing major site work, and it may be possible to adapt your code to suit.

    Regards,

    Martin

  • bensonbenson

    Hi Martin,

    Have a look at your pm for more about this.

  • bensonbenson
    edited February 20

    Hi Martin,

    This morning (early UK time) I made a SNR reading plot switching your antennas at 5 min intervals and thought you might find that interesting to have a look at.

    G8JNJ_9x5min.png

    It seems that your broadband inverted L antenna is indeed a good choice as RX default all round antenna, when checking at different times as well.

    best regards,

    Ben

  • G8JNJG8JNJ

    Hi Ben,

    Thanks for this, but for some reason I don't seem to have received your PM.

    If you have a look at the recent antenna thread, you can see a photo of some of my antennas.

    https://forum.kiwisdr.com/index.php?p=/discussion/3106/antenna-recommendation

    The main issue is not so much the actual signal levels, but the various interference sources. You can see this is you switch between the antennas whilst the waterfall is fully zoomed out. Various wide swathes of noise come and go depending on the directional characteristics of the antenna in use.

    The loops also highlight the problem, they all should have the same gain and frequency response as each other, but some orientations favour UK MF broadcast stations, whilst other place them in a null, and this also affects the SNR scores.

    Regards,

    Martin

  • jksjks

    Would it be possible to display the updated SNR values next to the Measure SNR now button ?

    Have that working now and it will be in the next release.

    The SNR values on the user and admin status tab are only updated every 10 seconds along with the other periodic statistics. When you click the Measure SNR now button it will update those values immediately, along with the values shown next to the button.

  • G8JNJG8JNJ

    Thanks for the SNR update, that will be very useful for testing.

    Regards,

    Martin

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