• Shortwave Radiogram, 20-26 June 2024, program 359

    From n2qfd@21:1/154 to All on Thursday, June 20, 2024 16:55:13
    View this email in your browser (https://mailchi.mp/fd130b9944c4/shortwave-radiogram-20-26-june-2024-program-35
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    **
    Shortwave Radiogram
    Program 359
    ------------------------------------------------------------
    Hello friends,

    During the "DX Headlines" segment on The Mighty KBC, Peter John has lately been sending a bewildering combination of digital modes and SSTV images, all packed in to one shortwave broadcast channel. Most of us are usually not successful in decoding them all, in part because the digital traces are below or above our receivers' passbands. But it's fun to try.

    Peter's experiments have encouraged me to try this on Shortwave Radiogram. Actually, I have tried simultaneous digital modes in the early days of VOA Radiogram. Because of the complexity of producing and decoding such content, I have not continued such transmissions on a regular basis.

    This week (program 359), we will experiment with
    transmitting two streams of MFSK32 simultaneously. One stream
    will be text about the red squirrels at the Yorkshire Arboretum
    in England. The other stream will be an MFSK32 image of a red
    squirrel.

    You can decode both streams simultaneously by running two
    instances of Fldigi. On one instance, the RxID should be on (as
    normal for most listeners). The RSID will switch the mode to
    MFSK32 (it should be there already) and the audio frequency to
    somewhere near 1500 Hz. On the other instance of Fldigi, turn the
    RxID off. Manually switch the mode to MFSK32 (if not there
    already) and the center audio frequency to 2100 Hz. A tone before
    the picture is transmitted will help you fine tune to the
    specific audio frequency. If all goes well, you will see the text
    and the image decode simultaneously.

    The alternative method is to record this edition of Shortwave
    Radiogram. Decode the text at (or near) 1500 Hz "live" with the
    RxID on. Later, from your recording, decode the image with the
    RxID off and the center audio frequency set near 2100 Hz, guided
    by the tone before the picture is transmitted.

    To avoid clipping, mixing products, and audio harmonics, the
    level of the combined MFSK32 streams was reduced by about 3 dB.
    The decode of this combined MFSK32 signal might not be as robust
    as from our usual single MFSK32 stream.

    The choice of a 2100 Hz center frequency for the second MFSK32 stream is deliberate. In decoding our MFSK modes, some listeners notice audio harmonics. I don't know if these are actually transmitted, or if they are a phenomenon within receivers. For our usual MFSK32 centered on 1500 Hz, the trace is from about 1250 to 1750 Hz. The second harmonic for that is 2500 to 3500 Hz. The second MFSK32 stream centered on 2100 Hz is from 1850 to 2350 Hz, thus sidestepping any interference from that second harmonic (if it exists in your receiver).

    It seems to me that it would be possible to design a shortwave receiver, conventional or software-defined, that could display both text and an image, or two streams of text, resulting from the transmission method we will use this week.

    A video of last week's Shortwave Radiogram (program 358) is provided by Scott in Ontario (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=b2d09a71b0&e=2e0721c4fa) (Wednesday 1330 UTC). The audio archive is maintained by Mark in the UK (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=edaeaf1745&e=2e0721c4fa) . Analysis is provided by Roger in Germany (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=93f879f904&e=2e0721c4fa) .

    Here is the lineup for Shortwave Radiogram, program 359, 20-26 June 2024, in MFSK modes as noted:

    1:44 MFSK32: Program preview
    2:52 MFSK32: Text at 1500 Hz and simultaneous image at 2100 Hz*
    7:33 MFSK64: Greener electronics to reduce e-waste
    12:25 MFSK64: This week's images*
    28:22 MFSK32: Closing announcements

    * with image(s)

    Please send reception reports to radiogram@verizon.net

    And visit https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8db
    7&id=8b238c108b&e=2e0721c4fa (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=9ce02c4de7&e=2e0721c4fa)

    Twitter: @SWRadiogram or https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8db
    7&id=fbdcb27103&e=2e0721c4fa (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=639e872e37&e=2e0721c4fa)

    (visit during the weekend to see listeners' results)
    Facebook group: https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8db
    7&id=a51deac56b&e=2e0721c4fa (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=347032a4c0&e=2e0721c4fa)

    Shortwave Radiogram Gateway Wiki: https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8db
    7&id=db168ced2c&e=2e0721c4fa

    Other Shortwave broadcast programs that include digital text and images include The Mighty KBC, Pop Shop Radio and Radio North Europe International (RNEI). Links to these fine broadcasts, with schedules, are posted here (https://swradiogram.us19.list-manage.com/track/click?u=43fc8ba8977b432a99e9b8d
    b7&id=93532de529&e=2e0721c4fa) .

    Thanks for your reception reports!

    Kim

    Kim Andrew Elliott, KD9XB
    Producer and Presenter
    Shortwave Radiogram

    N2QFD{Queen City BBS}:// "Does this need to be said? Does this need to be said by me? Does this need to be said by me right now?" - Craig Ferguson

    --- Mystic BBS v1.12 A48 (Raspberry Pi/32)
    * Origin: Queen City BBS (21:1/154)