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FT8 and ALC

Discussion in 'Working Different Modes' started by KB2E, Aug 29, 2018.

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  1. KD6RF

    KD6RF Premium Subscriber QRZ Page

    "Intermodulation distortion is the amplitude modulation (and generation of new related frequencies) of signals containing two or more different frequencies, caused by nonlinearities..." ----- FT8 is a single tone FSK modulation so there is no IMD of an FT8 signal, with out without ALC. However, other potential issues with ALC usage are described above, including possible problems right at the short tone shift time, depending upon time constants etc...

    IMD can happen on the RX side, and is often seen on the waterfall as a result of a very strong received signal or signals acted upon by the receiver's nonlinearity.[/quote][/quote]
     
    G0GSR likes this.
  2. KB2E

    KB2E XML Subscriber QRZ Page

    Yes, I see on the watrefall sometimes very wide and very "bright" signals. I assume they are high power or very dirty. I also notice that many times their signal report does not match how "strong" they look.
     
  3. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Exactly.
     
  4. PY2CYE

    PY2CYE Ham Member QRZ Page

    Sempre mantive o ALC no meio da escala. Entretanto depois que li estes artigos não vou usar ALC mais.
     
  5. W4HWD

    W4HWD Premium Subscriber QRZ Page

    Then why, on Elecraft rigs, is the ALC setup for FT8 shown as "4 bars solid with a flickering 5th"?

    I know the answer, do you?
     
  6. G0GSR

    G0GSR Ham Member QRZ Page

    Ft8 is not a perfect narrowband signal, it does contain significant sidebands outside its nominal 50Hz bandwidth.
    These diminish in amplitude very rapidly but CAN be seen clearly on stronger signals and is a normal "feature" for this mode.
    Frank
     

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