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Large masked band segments

Paul, VK3KHZ, from PK's Loop Antennas, brought to my attention the http://plonsk.proxy.kiwisdr.com:8073 Kiwi that has these very wide masked band segments (AKA notched, blacklisted).

How was this done? It turns out it's a feature/bug of the existing masked frequency option available with dx labels. Normally when you setup a dx label and set the "type" menu item to "masked" the width of the masked frequency area is the passband of the label's mode (AM, CW, ...) But the dx label panel also contains a "passband" field where you can specify a custom passband which overrides the default.

Well, it turns out you can specify a ridiculously wide passband too. The audio code will clamp an overly wide passband to 12 or 20.25 kHz depending on the Kiwi FPGA configuration, but the masked frequency code will happily take your crazy passband width and block a huge segment of spectrum. So creating a dx label at 1120 kHz with the passband field set to "1180000" (the passband field is always in Hz) would mask the entire NA 530 - 1710 kHz AM BCB (530 = 1120 - 1180/2, 1710 = 1120 + 1180/2). The passband field also accepts a "lo, high" specification (e.g. "300, 2700" for a USB passband). So you could specify an large asymmetrical masked segment as well (label at 6 MHz, passband "-1000000, 2000000" to get a masked segment from 5 - 8 Mhz).

Pretty cool. Thanks Paul!
Powernumpty

Comments

  • jksjks
    edited April 2020
    The v1.387 release allows you to use "k" and "M" suffix notation in the passband field, just like you can in other parts of the UI (e.g. frequency entry box). E.g. "2.1k" instead of "2100", "2M" instead of "2000000" etc. However the next time the dx label panel is opened the values are converted back to Hz again.
  • Looks like rx.linkfanel has redone his algorithm so as not to reward those stations with a ridiculously high SNR due to the large and/or numerous masked sections.
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