[Elecraft] serial interface noise on 160m -- propagates through K3

[Richard Ferch]

Mitch,

Has your K3 had the modification described in
<http://www.elecraft.com/K3/mods/ELECRAFT_Application_Note_Improving_the_Immunity_of_the_Rear-Panel_KIO3_RS232_and_Audio_Connectors_to_RF.pdf> 
performed on it - specifically, bypassing L1 as described at the top of 
p.4 of the application note?

I had serious noise pickup on the IF output from my K3, which pulsed in 
time with polls from my radio control software. The source was a 
USB-to-serial adapter connected to the K3's RS-232 jack. After I 
performed the above mod the problem disappeared. I did several other 
mods at the same time, so perhaps it wasn't this one that did the trick, 
but I suspect that it is what solved my problem.

73,
Rich VE3KI
K3 #1595


> Thanks to everyone who responded -- as far as directional antennas go the VX-3R yahoo \
> group pointed out that the hand held has a fairly directional AM antenna that can be \
> use to chase down noise.
> 
> I have been able to narrow the source of the noise down to the USB to Serial \
> converters or the USB Hubs themselves.  The noise is getting into the ground through \
> the serial interface on the K3 and then out to the coax shields.  I'll have to move a \
> heavy desk to determine which of the two potential offenders is actually generating \
> the noise.
> 
> I was curious if anyone else had experienced this with a K3 and USB<->Serial \
> converters -- the pulsing of the noise turns out to be HRD polling the K3 for VFO \
> position -- once every 300ms -- and when I turn off polling the noise stabilizes but \
> is still present.  I am doing research to see what I can do to eliminate it.
> 
> While chasing this down with my HT,  I found several other sources of noise -- all \
> within my shack, so I have a noise eradication project to embark on now.
> 
> 73,
> Mitch Mitchell, AE5HO
> mitchmitchell1616 at msn.com
>