[Elecraft] KAT500 set up

[Dick Dievendorff]

Is your K3 still hooked to the KAT500 via a 15-pin ACC cable and the KAT500
to KPA500 via another 15-pin ACC cable?   I'm wondering if your KAT500 has
two masters...

The KAT500 doesn't have a way to know whether the amp is in STBY or OPER.
But when you switch the amp to OPER, if one of the two key line inputs is
down, the amp will likely shift to transmit, and its T/R relay will
interrupt the Rx path.

The key line interrupt in the KAT500 uses a DPDT relay. 

One pole is used to break the key line that comes through a 15-pin cable
from pin 10 of the K3 ACC jack to the KAT500 and from the KAT500 thru
another 15-pin ACC cable to the back of the KPA500.  

Another relay pole is used to interrupt the path any radio that has a
back-panel KEY line (generally an RCA connector), thru the KAT500 to an RCA
connector on the back of the KPA500.  Those two paths are separate within
the KAT500.  

The same relay switches both paths, but there is no connectivity between the
15-pin ACC path and the RCA path.

However if EITHER path is held low, the KPA500 is likely to shift to
transmit.

I can't see how things are wired there so I'm guessing a bit here.

I think from your symptoms that you are somehow keying the amplifier (its
KEY line is being brought down) when you don't expect it to be.  The
KPA500's T/R switch interrupts the receive path.

You might want to try the cabling diagram from the KAT500 manual that shows
a K3 and KAT500 and uses the "key line interrupter" device that comes with
the KPAK3AUX kit - it looks like a little gender changer and mounts between
the KPA500 and the cable.  It breaks pin 10.  Then arrange so that all your
radios (K3 as well as others) use the same RCA key line path, and switch the
appropriate radio to control the RCA line that goes into the KAT500.  

A voltmeter on the KPA500's KEYIN line (with the RCA pin in place) might
clear up the mystery.

73 de Dick, K6KR



-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Mike Baird
Sent: Wednesday, November 21, 2012 11:38 AM
To: elecraft at mailman.qth.net
Subject: [Elecraft] KAT500 set up

Just received my KAT500 and got it all hooked up.  Works perfect with my K3
and KPA500.  However, when I try to use it with other radios on the desk,  I
have a problem.  All works OK when the amp isn't inline.  But, when using
another radio (other than the K3), and you put the amp in the operate
position, I get almost a muting of the RX.  This is before actually keying
the amp with my footswitch.  I've fiddled with the keying cables with no
success.  Didn't have any trouble when using the previous tuner (Palstar).
I must be missing something rather obvious.

 

Thanks for any help.

 

--Mike, W0RSR

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