Serial Comm pulsing noise issue on 40m

[Mark J. Schreiner]

I've noticed a fairly weak noise on 40m when using N1MM Contest Logging
program.  I have the correctly built pseudo-serial cable from the back
of either a laptop or a desktop compuker to the KIO2 port on the back of
the K2.  I've only noticed this noise when using the N1MM program,
although I should try it on some others as well.  I have used the KA3JWE
PA QSO Party software as well but didn't notice the same noise with
that.  The noise is a pulse about once per second and is not very strong
and spaced about every 5 kHz, (e.g. 7030, 7035, 7040, etc).  It is most
noticable during "quiet" band conditions.  I hear it louder on ANT1
which is actually connected to my outdoor antenna but I also hear it
much fainter on ANT2 which is not connected to anything.  If I
disconnect the cable from the back of the K2 the pulsing goes away.  If
I close the N1MM program the noise goes away.

I just tried the same with Win-EQF and I wasn't able to find any similar
issues (on 40m, didn't check other bands).  Also just tried the KA3JWE
PA QSO Party logging program and again didn't hear the same sort of N1MM
related pulsing sound.  Not sure how many other logging programs I
should try to download to try.

Oh, I tried wrapping the pseudo-serial cable around a ferrite choke,
three turns, sorry I don't know much specifics about the ferrite
material, probably one of those from Radio Slack, it is in a white
plastic snap together housing, about 1" square with a hole that is okay
for maybe RG8 coax at most.  That had no affect on the pulsing noise.  
Wrapped the wire around the choke near the rig (about 4" from the
connector).

Has anyone else experienced this?  Anyone come up with a solution or
have any other ideas for me to try?

Thanks!

Mark, NK8Q

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[Stuart Rohre]

Use of ferrite cable chokes is not just put it anywhere.

You have to slide it along the cable and find the point of maximum
attenuation of the noise, if it is on the cable at all.  You then afix the
choke with nylon cable ties so that it can maintain its position on the
cable "sweet spot".  Likely you may need it closer to the computer device.
But, you have to try every point.

Stuart
K5KVH


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