Dirty JT65 Transmit

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  • Updated 4 years ago
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I seem to remember reading a few posts about dirty transmit signals, well tonight I got mine.

I had my 6500 running for probably a week without a restart.  I have been working CW mostly trying to get the K5P and VP8 stations.

I went up to 40m LSB and did a few short QSO with the amp on.  I switched to the provided radiosport profile and got good results.

I then decided to play some JT-65.  The signal didn't look right and my computer speakers were making a little noise I wasn't used to hearing but a guy did come back.  However when I called CW someone sent:


So I did Ken's trick and did the xvrtr and full duplex and yes it was nasty.  I played with DAX gain, nothing seemed to help.  So I simply quit everything, remote depowered the radio, restarted it and now the signal is clean under the same exact configuration.

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Mark - WS7M

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Posted 4 years ago

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Photo of Ray Andrews, K9DUR

Ray Andrews, K9DUR, Elmer

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Official Response

Jon is correct.  This is a pernicious little bug where the DAX signal becomes corrupted if DAX is running for a couple of days.  Closing & re-starting DAX always fixes the problem.  This is not unique to JT-65, but applies to all digital modes.

I am on the alpha team, but have not been able to determine a set of circumstances that causes it except for a random length of time - usually 2-3 days.  Therefore, it is almost impossible to give any guidance to the developers to help them track it down.

73, Ray, K9DUR