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Re: [wsjtgroup] An observed Sig-Rep I made btw JT65 & JT9

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  • Joe Taylor
    Hi Brian, JT65A uses detection bandwidths 2.69 Hz, and JT9 uses 1.73 Hz. So yes, JT9 will have somewhat greater difficulty with frequency drift. The decoders
    Message 1 of 12 , Sep 13 4:28 PM
      Hi Brian,

      JT65A uses detection bandwidths 2.69 Hz, and JT9 uses 1.73 Hz. So yes,
      JT9 will have somewhat greater difficulty with frequency drift.

      The decoders for both JT65 and JT9 include "AFC" algorithms that try to
      detect and remove moderate amounts of frequency drift. The AFC routine
      in JT65 has been tested and optimized more thoroughly, and because of
      the greater fraction of signal energy put into the Sync tone, it
      probably works better. It may be possible to improve JT9's handling of
      drifting signals, somewhat.

      -- Joe, K1JT

      On 9/13/2013 6:39 PM, Brian Duffell wrote:
      > Joe Taylor<joe@...> wrote:
      >
      >> The bottom line is that the two modes have comparable sensitivity. Under
      >> benign propagation conditions JT9 has a small (1-2 dB) advantage over
      >> JT65, and of course it uses less than 1/10 the bandwidth.
      >
      > I recently changed my rig. The new one seems to drift a few cycles with heat
      > over a 46/50 sec transmission by about 3 hz (at 10MHz, other bands pro
      > rata)whereas the old one didn't.
      >
      > Decodes in JT65 seem unaffected but JT9 seems to suffer particularly on the
      > higher HF bands. Is this due to a lower immmunity to frequency drift for
      > JT9?
      >
    • Thomas F Giella W4HM
      I have had 5 pre-arranged DX QSO s on 15 meters using JT9 followed immediately by JT65A. Power output was always 1 watt to a 288 ft long horizontal loop up at
      Message 2 of 12 , Sep 14 6:54 AM
        I have had 5 pre-arranged DX QSO's on 15 meters using JT9 followed
        immediately by JT65A. Power output was always 1 watt to a 288 ft long
        horizontal loop up at 35 feet. Rig was an Icom IC-7600. At these times radio
        wave propagation was pretty stable.

        On every QSO JT9 beat JT65A by approximately 3 db. There were instances
        where the JT9 signal got through but the JT65A signal did not.

        73 & GUD DX,
        Thomas F. Giella W4HM
        Lakeland, FL, USA
        w4hm@...

        BARTG #8531
        PODXS 070 #349
        FELD HELD #141
        30MDG # 691
        DMC #1243
        WARC-CC #20

        W4HM Amateur Radio & SWL Autobiography: http://www.w4hm.org
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