KPA500 Aux Cable Pin 11 Problem with Preamp

[Mike K2MK]

I had a problem that I remembered reading about on the reflector when I hooked up my new KPA500 to my K3 with PR6/10 preamp using the Elecraft Aux cable and the companion Y cable. I searched the archive and discovered that users found it necessary to remove pin 11 from the cable to the KPA500. The problem I experienced was that the preamp was powered up on all bands not just 6/10/12 meters. I only noticed it when I tried to use my separate receive antenna on 80 and 40 meters. Since the preamp was powered up the RX ANT bypass in the preamp did not function so the K3 never saw my receive only antenna. Removing pin 11 from the Aux cable to the KPA500 solved the problem.

I'm surprised there is no mention of this problem and its solution in the KPA500 manual. I think an alert should be added.

73,
Mike K2MK

[James Rogers]

I also had a problem with an external preamp for 6 meters.  This one I
powered from the station 13.8V power supply so it was always on. The
problem came about when I changed bands to the internal 2M transverter
and inadvertently activated the RX ANT.  Instant relay buzz from inside
the K3, I assume it originated from the KXV3A board.  Removing power
from the external preamp cured the buzz.  A bit of a mystery in that the
KXV3A has DC blocking caps on the IN and OUT connectors as does the ARR
P50VDG preamp.  As my activation of the RX ANT was inappropriate for
2M,  I have not made an issue of the anomaly.  I am still very curious
as to how and what caused the relay buzz?  Everything is the shack is
single point grounded including the station power supply.

73s Jim,  W4ATK
On 5/9/2014 7:34 AM, Mike K2MK wrote:

> I had a problem that I remembered reading about on the reflector when I
> hooked up my new KPA500 to my K3 with PR6/10 preamp using the Elecraft Aux
> cable and the companion Y cable. I searched the archive and discovered that
> users found it necessary to remove pin 11 from the cable to the KPA500. The
> problem I experienced was that the preamp was powered up on all bands not
> just 6/10/12 meters. I only noticed it when I tried to use my separate
> receive antenna on 80 and 40 meters. Since the preamp was powered up the RX
> ANT bypass in the preamp did not function so the K3 never saw my receive
> only antenna. Removing pin 11 from the Aux cable to the KPA500 solved the
> problem.
>
> I'm surprised there is no mention of this problem and its solution in the
> KPA500 manual. I think an alert should be added.
>
> 73,
> Mike K2MK
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/KPA500-Aux-Cable-Pin-11-Problem-with-Preamp-tp7588821.html
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