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9170Re: JT65/JT4 - Max sync values + frequencies

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  • booz2m
    Oct 4, 2012
      Hi Joe et al,

      Thanks for the sync clarification and confirmation. Also OK about the bandwidth.

      The reason for asking was an abnormal behavior I experienced that caused some head scratching. I am on the process of finalizing the S/W for the Next Generation Beacon http://rudius.net/oz2m/ngnb
      When I made the JT65_2 modes I, for some reason, tested with only a call (OZ7IGY/A) and I could not get any decode despite perfect sync. When I added the square (JO55) or used the raw call (OZ7IGY) and locator (JO55WM) it all went well.
      For beacon purposes the message is sent in freetext format. But, it seems as if a to short a message, that is padded with spaces, is interpreted as formatted text and thus is not decoded in WSJT. Not a big thing though as this is probably only seen when testing with only a callsign.

      However, I also saw a somewhat similar behavior in WSPR if power is not ending in 0, 3 or 7. I sent "OZ7IGY JO55 44" and it comes out as B5L7/OZ7IGY 43 in the WSPR program. As far as I can see the WSPR protocol is "power transparent" with 6 bits? Or am I wrong?

      Finally, one question: Do you know how robust JT65C's are to distortion like aurora and rain scatter? Empiric data show that JT4G works with rain scatter. I guess the 65 tones will be blurred and overlapping. Four tones with adequate spacing are probably less prone to this.

      Bo, OZ2M
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