How to identify digital modes

Discussion in 'Working Different Modes' started by M0AGP, Feb 10, 2021.

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  1. M0AGP

    M0AGP Ham Member QRZ Page

    Some modes are very easy to identify by eye or because of the frequency, or by sound.

    I'm wondering if there might be a piece of software someone has written that would let you define a passband and it tells you what kind of signals are there.

    What prompted this was listening on the 10m FT8 frequency and hearing a very faint tone - noise was high enough that I couldn't tell if there was a FSK-type warble. There were no other signals on 10m in the CW/data area.

    Checking the waterfall, sure enough there was a trace that was on for just under a minute, off for a minute etc.

    I switched WSJT-X to the JT9+JT65 mode - no decode. I switched to the 60 second cycle of FST4 - nope.

    Of course it could have been a ham that was just "tuning" without any modulation, and that for 5 minutes straight kept repeating this specific pattern... but the simplest explanation is that it was a mode that is not in WSJT-X. Right?

    OR for some reason I could hear the sound faintly and easily see the trace on the waterfall, but it was not strong enough for a decode...? Sounds unlikely ...

    I guess I could install something like FLdigi and use trial and error...

    Is there an automatic digital mode detector?
    Last edited: Feb 10, 2021
  2. KY1K

    KY1K Ham Member QRZ Page

    I generally look at the waterfall to figure out the mode.
    The timing and width are a good starting point.
    60 second cycle and 200hz wide is jt65, 10hz is jt9.

    If I don't recognize it, I use this website

    Auto detection would be almost impossible with consumer computers (the number of different decode attempts needed per cycle) and made even worse by less than perfect noise conditions. I know SSTV has mode identified- I think my a data burst at the start? So it can be done with a limited set of options
    KD9VV, PU2OZT and M0AGP like this.
  3. K3XR

    K3XR Ham Member QRZ Page

    There are some very talented folks in our hobby on the computer/software side of things. Maybe one day a program will exist that analyzes the signal and identifies the digital mode. This would be a big help for a mode like Olivia. I noticed also that when I work SSTV with MMSSTV is does detect the format.
    M0AGP likes this.
  4. M0AGP

    M0AGP Ham Member QRZ Page

    Thanks - my first guess was JT9 or JT65. Maybe it was but there was no decode for some reason...

    I like the idea of going onto a "dead" band and making contacts using very sensitive digital modes...
  5. KY1K

    KY1K Ham Member QRZ Page

    The 9/65 dual decode has never worked well for me.

    I have a friend that lives in a condo about 50 miles away. He does good in FT8 at the 900-1300 mile range but nothing closer.
    We were playing on 80m and I spotted him once at -24 but couldn't complete a QSO. He was simply buried in the noise.
    We switched to JT9 and the silent frequency plus narrow bandwidth made the QSO on the first try. Like -12 or so. It really shows what the crowded 3kHz does to weak signals!

    I often tune to 10,12,15 digi and send out a CQ. The dead band instantly comes alive!
    M0AGP likes this.
  6. K3YES

    K3YES XML Subscriber QRZ Page

    Agree with OP's inquiry and hope that some smart people might be able to figure out some kind of signal identifier software. Should someone write it, I would use it.

    But along the lines of websites to look at to identify signals, here's a vote for a site that shows multiple signals side-by-side, shows relative bandwidths, and one click leads to a sample sound file:
    M0AGP, KY1K, PU2OZT and 1 other person like this.
  7. KD9VV

    KD9VV Ham Member QRZ Page

    The sig ID link above is a great reference for ham freqs.
    That said, non-amateur signal decoding can be especially tricky; especially when one considers many non-ham digital sigs are encrypted.
    They sound normal but can not be decoded without a psuedo-random key.
  8. W1VT

    W1VT Ham Member QRZ Page

  9. 2E0CIT

    2E0CIT Ham Member QRZ Page

  10. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    you're right... I think this might be the repository:
    2E0CIT likes this.

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