[Elecraft] KAT500 80 meter anomaly

[Lyn Norstad]

EDIT:  Don't be confused when I say "L/C" but express the values as "C/L."
You know what I mean ... 

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Lyn Norstad
Sent: Tuesday, July 06, 2021 3:48 PM
To: Elecraft at mailman.qth.net
Subject: [Elecraft] KAT500 80 meter anomaly

On 80 meters, the KAT500 stores frequencies in memory every 10 kHz.  Because
of bandwidth issues, normally that's a good thing.  Except when it isn't.

 

Many digital modes that use prescribed frequencies are clustered in a fairly
narrow region.  For example ("dial frequency" in kHz):

 

FT8 = 3573.000

FT4 = 3575.000

 

Winlink 80m Gateway 1 = 3586.000

Winlink 80m Gateway 2 = 3595.000

 

If you only operate FT8 and FT4, there is no issue.  Likewise, if you only
operate Winlink in that region, no problem.  But if you operate both, the
KAT500 can't seem to recall the exact settings for any of those frequencies
consistently.

 

Here's an experiment for you to try, if you're interested:

 

1)    Clear the frequency memory for 80 meters on whatever antenna you use
(KAT500 configuration>Erase Antenna Tuner Memories).

2)    Using the same utility, "Memorize" a setting for each of the four
above frequencies.

3)    Conduct a Winlink VARA HF session at both 3586 and 3595 kHz (if you
can't connect to any stations, that's OK too).

4)    Then using WSJT-X software, do a brief session using FT8 and then FT4.

 

So far, so good.  Everything works great.

 

But now go back to the Winlink software are try to check for mail using the
same frequencies, 3586 and 3595 (it would be nice to connect this time).  If
your system works like mine, on every other transmission it will hunt for a
new match (even if it's already 1:1).  In my case, the "normal" L/C values
are:

 

@ 3573 = 0 / 6500

@ 3575 = 0 / 6500

 

@ 3586 = 180 / 6500

@ 3595 = 180 / 6500

 

When the KAT500 goes a little bit crazy with its "every other time hunt" on
the Winlink frequencies (3586 and 3595) it will jump to some extremely high
SWR value (in the 80s or 90s) and then eventually settle back with an L/C of
. say . 0 / 5400 (creating settings for 3592 kHz).  Meanwhile, the Gateway
station has very likely lost at least half of your transmission.  This
behavior is independent of Automatic or Manual settings, exciter power
settings, KPA500 On or Off (but OFF is better for testing, for obvious
reasons).

 

Is there a Command that would help to alleviate this behavior?  Or a way to
tell the KAT500 to ignore one or more of its preset frequencies that are
causing issues?

 

 

73

Lyn, W0LEN

 

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