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ka9q

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ka9q
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  • "Update: after noting that they were running 9 KHz BW, I pulled the corners of the passband in a tad and got an SNR improvement." But does this actually help? I don't know the details of the DRM decoder implementation and how the displaye…
    in DRM Heard Comment by ka9q February 2020
  • China National Radio DRM confirmed in San Diego CA on 7360 kHz at 0645 UTC on Feb 11, 2020. Mode B, 10 kHz, long interleaver, 4QAM SDC, 16QAM MSC, Protect A=1 B=1, Services A=1 D=0. AAC @ 14.56 kbps. UEP 20.7%.
    in DRM Heard Comment by ka9q February 2020
  • There's an apparent bug in the inactivity timeout. It doesn't seem to recognize local IPv6 users as local, so it still times them out.
  • Excellent. I'll dig into the code and see what I can do. I haven't looked, but I take it that your "native" audio format is 12 kHz PCM, 16 bits/sample? I generally use 48 kHz, but anything that divides it should be easy to use. Re my DRM …
  • Here in San Diego, I also see them all over the place (below the MUF, of course). I know that there are some over-the-horizon sea-state chirped radars near here. I suspect there are also some ionospheric sounders.
  • DRM has been a real disappointment out here in San Diego. Few stations transmit it, and none of them have been strong enough to decode. Late at night I can regularly see, e.g., China on 6030 kHz or WINB on 7315, but their SNRs are never high enough …
    in DRM Heard Comment by ka9q January 2020
  • Has he given a reason for requiring a login? Many websites seem to have done this, or at least added captcha challenges, to defend against high-volume abuse. That might be the case here.
  • Has anybody contacted him and asked for a reason? Maybe he was getting abused by non-hams?
  • I use Zeroconf to find local devices and services. That's a set of IETF standard protocols that originated as Apple's "Bonjour"; they're especially popular for discovering local printers. The KiwiSDR already runs 'avahi', which is the main…
  • Oh yes, doubles are terrible (and totally unnecessary) for DSP even on the x86. I use 32-bit floats for all data samples. Frequencies and quadrature oscillators still use doubles.
  • Are you tracking upstream Debian security updates? I consider frequent updates critical to system security, so if we're not supposed to do our own Debian updates then you'll have to take that over.
  • I recommend turning off password authentication in SSH if at all possible. In my opinion, this is the single most important thing you can do to secure ANY UNIX-like system on the Internet. Automated password-guessing attacks on SSH servers have been…