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JT9 use on 6 meters

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  • ka9cfd
    To K1JT Joe: I tried using JT9 on 6 meters today with not much luck. I was seeing J69DS trace easily on the waterfall but just a couple of decodes. The problem
    Message 1 of 2 , Jul 29 2:55 PM
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      To K1JT Joe:


      I tried using JT9 on 6 meters today with not much luck. I was seeing J69DS trace easily on the waterfall but just a couple of decodes. The problem appears to be a slight receiver drift in my Yaesu FT2000. I was wondering if it is possible to introduce an AFC button for JT9 operation that would lock on to the trace that you are trying to receive and compensate for any radio drift? I am using WSJT-X ver. 1.3, r3673. If there is a more recent version, I would like a link to it.


      73 Jay KA9CFD



    • Joe Taylor
      Hi Jay, ... It s hardly accidental that the docs explain that JT9 was designed for the LF, MF, and HF bands. Even 10 m is s stretch, with some radios and some
      Message 2 of 2 , Jul 30 6:04 AM
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        Hi Jay,

        KA9CFD wrote:
        > I tried using JT9 on 6 meters today with not much luck. I was
        > seeing J69DS trace easily on the waterfall but just a couple
        > of decodes. The problem appears to be a slight receiver drift
        > in my Yaesu FT2000. I was wondering if it is possible to
        > introduce an AFC button for JT9 operation that would lock
        > on to the trace that you are trying to receive and compensate
        > for any radio drift? I am using WSJT-X ver. 1.3, r3673. If
        > there is a more recent version, I would like a link to it.

        It's hardly accidental that the docs explain that JT9 was designed for
        the LF, MF, and HF bands. Even 10 m is s stretch, with some radios and
        some propagation conditions.

        Like JT65, the JT9 decoder does have an AFC as part of its bag of
        tricks. It's always engaged, solving for a linear frequency drift term
        before decoding is attempted. The algorithm can perhaps be improved.
        It's a tougher job with JT9 than with JT65 -- not least, because the JT9
        protocol devotes only about half as much time to a synchronizing tone,
        compared with JT65.

        Much better to use JT65A on 6 meters; the extra-narrow bandwidth of JT9
        is hardly needed on 6, anyway.

        -- 73, Joe, K1JT
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