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n6gn

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n6gn
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  • Quick comparison between the PA0RDT Mini-Whip and The RA0SMS Mini-Whip

    I have found it very worthwhile to use toroidal 'choking' in the form of a Guanella balun simultaneously on all lines going in/out of my KiwiSDRs.

    as shown in the bottom portion of the figure.

    Like the situation so nicely described by G3TXQ's graphic, suitable cores need to be used, possibly several of them to cover the broad frequency range of the Kiwi. By winding equal turns in the same direction with each line on a single core, the effective current that can flow through the receiver is reduced by the "transformer action" of the cores. Current that would otherwise flow into and through the SDR creates common flux within the core that causes an opposite current to come out, thus pushing total current toward zero and effectively creating a much higher impedance than can be the case when each line has only a dedicated core.

    From my experience, CM currents through the entire KiwiSDR structure produce IZ drop that appears across the effective ADC input, which is a complex function of PCB layout and conductivities - the "attenuator problem". For this reason, I believe, treating all lines as common mode lines, in addition of course to also eliminating differential noise across pairs of individual conductors of those lines, e.g. power line or inter-pair CAT5 noise, can be very effective in improving the KiwiSDR noise floor.

    Glenn n6gn
    Powernumptysesykes71
  • Noise advice for MiniWhip?

    How about a spectrum instead, there's information in that display that is hard to see in the waterfall.
    WA2ZKD
  • Suggestion - FT8 decoder?

    I think this is correct, that's how I generated these spots, by running on a moderately capable desktop. Judging from the relative performance of the KiwiSDR WSPR extension and other systems, I think asking an FT8 extension on the KiwiSDR to keep up with a band like 40m is lately is probably not realistic. I posted this in response the "Doable on the Kiwi?" question at the top of this thread. I suspect it really isn't....
    Glenn n6gn
    WA2ZKD
  • Some Observations While Using the KiwiSDR to Spot WSPR Stations [fixed in v1.242]

    Gwyn Griffiths, G3ZIL gwyn@autonomousanalytics.com , Glenn Elmore, N6GN
    n6gn@sonic.net, Rob Robinett, AI6VN, rob@robinett.us

    Abstract

    This article is intended to document some of our recent experiences using a KiwiSDR on WSPR and observed degradations of those spots when compared with other receiving and decoding techniques. Three techniques are examined: complete decode of WSPR stations by way of the KiwiSDR WSPR extension, use of the KiwiSDR to downconvert to an audio file which is decoded by a remote host, and for contrast a non-KiwiSDR path using an Apache Angelia SDR board. These comparisons show degradations in the two KiwiSDR paths both in terms of SNR of spotted stations and in number of stations spotted. Additionally these investigations have identified spurious signals associated with the downconversion process within the KiwiSDR.

    [download article PDF below]
    KA7UGene
  • Some Observations While Using the KiwiSDR to Spot WSPR Stations [fixed in v1.242]

    Gwyn Griffiths, G3ZIL gwyn@autonomousanalytics.com , Glenn Elmore, N6GN
    n6gn@sonic.net, Rob Robinett, AI6VN, rob@robinett.us

    Abstract

    This article is intended to document some of our recent experiences using a KiwiSDR on WSPR and observed degradations of those spots when compared with other receiving and decoding techniques. Three techniques are examined: complete decode of WSPR stations by way of the KiwiSDR WSPR extension, use of the KiwiSDR to downconvert to an audio file which is decoded by a remote host, and for contrast a non-KiwiSDR path using an Apache Angelia SDR board. These comparisons show degradations in the two KiwiSDR paths both in terms of SNR of spotted stations and in number of stations spotted. Additionally these investigations have identified spurious signals associated with the downconversion process within the KiwiSDR.

    [download article PDF below]
    KA7UGene