Setting Dispalyed Bandwidth

K4LEDK4LED
in KiwiSDR Discussion
I need to set the waterfall display bandwidth as follows. 15 to 30 MHz
Thanks
Larry

Comments

  • KA7UKA7U
    append this to the URL of the kiwi you are working with. ?f=22500.00amz1
    Ron
    KA7U
    K4LED
  • jksjks
    edited February 2019
    Hi Larry. If you're talking about the kiwirecorder and/or kiwi_nc (netcat) Python programs as we discussed in email then the situation is a bit different from the browser interface on the Kiwi itself (Ron's answer is excellent).

    When you use the "--wf" option with kiwiclient (i.e. as used by the "wf:" target in the Makefile) what happens is the Kiwi sends waterfall data at zoom level zero (0 - 30 MHz) at a 1 Hz update rate by default. The data is 1024 bins wide which is the size of the waterfall FFT and also how many bins are seen on the browser interface. So at zoom=0 each bin represents roughly 30 kHz of spectrum (30 MHz / 1024 bins ~= 30 kHz).

    I recall you said your analysis application wanted 512 bins of input data. So one thing you could do is simply throw away the first 512 bytes of output data on each update. Then you'd be left with 512 bins of data for 15 - 30 MHz. Now there is a --zoom option in kiwiclient as well but it turns out it isn't implemented quite correctly at the moment. It would be easy to fix however and then together with the -f option to set the center frequency you could set whatever power-of-two zoom sub-multiple of 30 MHz you wanted. For example as Ron said set the frequency to 22.5 MHz (the middle of the 15-30 MHz segment) and zoom=1. Then you'd get 1024 bins beginning at 15 MHz each with about 15 kHz of resolution.
    K4LEDheliosh
  • K4LEDK4LED
    John and Ron Thanks. I finally got it with your help. I need to get more familiar with basic operation. By the way the kiwisdr.local:8073 would not work on my Win 10 machines as noted in the instructions but using its IP (192.168.0.13:8073 in my case) it works fine. Thanks John for all your work on this project. Wonderful job. Do you have any suggestions on who might want to tackle my Kiwi to RSS project?
  • helioshheliosh
    Sorry to hijack this thread; is it possible to have more bins in the waterfall diagram for high resolution displays?
  • jksjks
    edited February 2019
    @heliosh The short answer is no. Using larger FFTs for the waterfall would not allow the realtime response requirements to be met. The FFTs are already internally computed at 8k for various reasons. See the design review document for details.
  • K4LEDK4LED
    John. Yes I absolutely understand that John not a problem. I appreciate the information you have provided and it is very valuable. I hope to stumble across something eventually. Like I said we are and have been using the FSK analog spectrograph receivers built by Dick Flagg which work but the new SDR receivers like SDRPlay as an example are so much more sensitive and have less noise being digital. SDRPlay has a nice RSS interface written by Nathan but its limited to 8 MHz and has other undesirable artifacts. I also tested LimeSDR with SDR# that has an RSS interface but it isn't perfect either. Lot's of birdies since the LimeSDR USB was not designed with HF in mind.That's why we are searching for a a better alternative. I hope we can get KiwiSDR working into RSS someway. I'll let you know if/when I come up with anything. Thanks again.
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