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DPRK DRM testing

jksjks
in Signals Received
As reported on Twitter #drmlog: DPRK DRM testing 3205 kHz

Little to no audio heard as most all rx locations had significant selective fading and the transmission parameters selected were not optimal for those conditions.
Screenshot from rx in Japan at 11:16 UTC. Note poor MSC 64 QAM IQ constellation explains why the MSC indicator is showing yellow (must be green for audio to be heard).
Also, they're not using long interleaving (i.e. ILV "L") which is probably a mistake.

image

Attachments:
https://forum.kiwisdr.com/uploads/Uploader/6f/5f8497ee7640743b3796bc57e18a1e.png

Comments

  • ka9qka9q
    Note also that they're 50 Hz low (or they were about 8 hours ago when I last looked). I don't know how well the KiwiSDR DRM decoder tracks frequency errors, so I retuned manually. (Didn't help because the signal was just too poor).

    It's easy to fine-tune DRM manually. Relative to center frequency there's a null at 0 Hz (to minimize QRM from co-channel AM carriers) and unmodulated pilots at +750, +2250 and +3000 Hz. Zoom way in on the waterfall and these features are easy to see.
  • jksjks
    The DRM mistuning detection is extremely good. Screenshot below is Radio Marti, received in PA, mistuned by +1 kHz (!) It locks and decodes fine. It also probably helps that they are running a very conservative configuration.

    The DRM spec has a little more information about the frequency pilot cells, section 8.4.2, page 121, http://kiwisdr.com/files/DRM/DRM.spec.v4.1.2.pdf

    image

    Attachments:
    https://forum.kiwisdr.com/uploads/Uploader/fb/df9d7aae206527de747fa8818aae52.png
    ka9q
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