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Re: [wsjtgroup] If possible...

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  • Joe Taylor
    Hi Jean, Many thanks for your suggestions! There are good reasons for the design choices that set the default JT65 sync tone frequency to 1270 Hz, and the
    Message 1 of 3 , Mar 11, 2009
      Hi Jean,

      Many thanks for your suggestions!

      There are good reasons for the design choices that set the default JT65
      sync tone frequency to 1270 Hz, and the default condition so that "TxDF"
      does not automatically track the setting of "Freeze DF".

      JT65 was conceived and designed for EME communication at VHF and UHF.
      The sub-mode JT65A is used for 50 MHz EME, JT65B for 144 and 432 MHz,
      and JT65C for 1296 and 2304 MHz. In the "C" mode the highest tone is
      711 Hz above the sync tone; the 1270 Hz default setting keeps that
      highest tone well within a SSB transceiver's filter passband.

      In EME communication there are many reasons that received values of "DF"
      may not remain constant. We are talking about frequencies one to two
      orders of magnitude higher than typical HF frequencies, so oscillator
      drift is much more of an issue. Even with stable oscillators, Doppler
      shifts on the EME path mean that received frequencies don't stay
      constant. Unlike typical operation with JT65A at HF, EME operators may
      frequently change the setting of "Freeze DF" during a QSO. They do
      *not* want their Tx frequency to change after such adjustments have been
      made.

      You made no particular case for 1500 Hz rather than 1270 Hz, or for
      "center, not edge", so I can't evaluate your reasoning. However, I do
      understand that the use of JT65A at HF would be more convenient and
      better behaved if some default settings were different for HF and for
      VHF+. Since the program has a "Band" setting, it should be possible to
      use this to "have it both ways", as appropriate for the frequency in use.

      I have no idea what fraction of JT65 users on HF are using MultiPSK,
      instead of WSJT. That, of course, would be another issue.

      -- 73, Joe, K1JT

      jean wrote:
      > Joe,
      >
      > If you are planning a new soft for HF use, I should like
      >
      > -- transmission centered on 1500 Hz,(center, not edge), not 1270
      >
      > --AND BEFORE ALL :
      >
      > An auto transceive feature as a default : click anywhere in receive, and
      > the tx follows...
      > It appears that now one qso out of 2 is in split, and takes 2 freq when
      > one is enough.
      > Yet this morning, two cq on 14075.75, two answers on 14076... and two
      > qso on double freq. Impossible to TxDF on the caller's freq, he thinks
      > he lost me !
      > With the increasing number of new stations trying JT modes, it happens
      > all the time. Many are unable to read the help or do not understand what
      > they are reading !
      >
      > Best 73.
      >
      > Jean F8RZ
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