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FT8- pick a clear frequency

Discussion in 'Amateur Radio Software' started by W1XWX, Aug 12, 2017.

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  1. W1XWX

    W1XWX XML Subscriber QRZ Page

    Just an FYI for the new mode FT8. When using WSJT-X I have noticed the signals all clustered together in one section of the waterfall. Hold down the control key and click an open spot on the waterfall before you transmit CQ.

    Many times I see multiple people on or overlapping other people who are transmitting. Probably most do not realize they are doing this especially if they close the waterfall and just use the main screen on WSJT-X. 73

    W1XWX
     
  2. VA3VF

    VA3VF Ham Member QRZ Page

    People close the waterfall window? Why would they do that? If this is widespread, I now understand why we see so many people TXing on top of others. I was giving them the benefit of the doubt, new mode and new software, but my 'goodwill' is wearing thin. :(

    On a related topic...why do people send me signal reports, RRR, and 73 when I'm not in contact with them. What's the deal here?

    73 de Vince, VA3VF
     
  3. KV6O

    KV6O Premium Subscriber QRZ Page

    This is nothing new, just because you see two signals overlapping doesn't mean that either station can hear/see each other due to propagation. Happens on JT65 all the time.
     
  4. ND6M

    ND6M Ham Member QRZ Page

    I have seen several post concerning this, but, in my experience, the software can and does decode signals that are "on top" of each other, even when one is much stronger than the other.

    Agreed, ......it seems to go against "proper" radio etiquette

    C/P from the WSJT site:

    Some important characteristics of FT8:

    - T/R sequence length: 15 s
    - Message length: 75 bits + 12-bit CRC
    - FEC code: LDPC(174,87)
    - Modulation: 8-FSK, tone spacing 6.25 Hz
    - Constant-envelope waveform
    - Occupied bandwidth: 50 Hz
    - Synchronization: 7x7 Costas arrays at start, middle, and end
    - Transmission duration: 79*1920/12000 = 12.64 s
    - Decoding threshold: -20 dB; several dB lower with AP decoding
    - Multi-decoder finds and decodes all FT8 signals in passband
    - Optional auto-sequencing and auto-reply to a CQ response
    - Operational behavior similar to JT9, JT65


    BTW: the reason some people seem to use certain offset freqs has to do with the clarity of the sent tones, they are much "cleaner" @ the higher offsets.
     
  5. VA3VF

    VA3VF Ham Member QRZ Page

    Finding all signals in passband does not mean on the same frequency, but I do see 2 on-frequency decodes sometimes. Never more than two, like in JT65. Your quote from the WSJT site does not mention multipass decoding. I believe this is how multi on-frequency decode is achieved in JT65. I think I saw it listed as one of the features to be implemented in FT8, but I may be wrong.

    If I understand what you are saying about the offsets, this is solved by enabling split in WSJT-X.
     
  6. NS8N

    NS8N Premium Subscriber QRZ Page

    I was guilty of the first 2 posters rants. Today, I made my first ever digital contact (been hamming for a while).

    It came down to...I didn't know what I was doing! I had read lots before putting my rig on the air but still let my software dictate the default frequency to transmit on.

    As far as VA3VF ...I did that too, accidentally. While I appreciate all the work the devs put into the software, it seemed unintuitive to me. It turned out I had to check another box and I was all set.

    Fun mode. But it's new. So expect dummies like me who don't know what they are doing and have patience. 73 all. FT8 IS A FUN MODE SO FAR
     
  7. VA3VF

    VA3VF Ham Member QRZ Page

    Not a problem. :) My mood changed a bit today because it was happening too frequently. When the frequency matches to the Hz, there is more than a coincidence, I think. :rolleyes:

    Then there are the frequency 'stealers'. They answer your CQ, complete the QSO, and then proceed to call CQ themselves, on the same frequency you were using for the longest time.

    Nobody has volunteered an explanation for those people who send me signal reports, RRR, and 73, when I'm not in contact with them. :confused:

    Don't be afraid to make mistakes, and don't be afraid to ask here, or on other forums, for assistance.
     
    W1XWX likes this.
  8. KC3RN

    KC3RN Ham Member QRZ Page

    That has happened to me several times this weekend...... Maybe people forget to check "Lock TX/RX" when they start transmitting. I usually start that way, then unlock after I start a QSO.
     
  9. W1XWX

    W1XWX XML Subscriber QRZ Page

    Well the mode is new and even WSJT-X is new to many hams. Just hold down the CONTROL key and click on a free area on the waterfall before you start transmitting CQ. This is NOT obvious to new users of the software -- only to seasoned digital operators. Usually transmitting on top of someone is simply an accident. 73
     
    NS8N likes this.

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