[Elecraft] Using Elecraft KPA-1500 for 2 radios

[Ken K6MR]

I have been using 4 of these switches to share one amplifier between two K3s in an SO2R setup for the past 4 years.  I was running two KPA500s in parallel, but recently switched to a KPA1500.  No problems.



I don’t operate 6 meters, and 10 meters hasn’t been open in so long I can honestly say I don’t operate there either!



Ken K6MR



________________________________
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> on behalf of Tom Georgens <tomgeorgens15 at gmail.com>
Sent: Monday, March 18, 2019 6:01:04 PM
To: jim at audiosystemsgroup.com; elecraft at mailman.qth.net
Subject: Re: [Elecraft] Using Elecraft KPA-1500 for 2 radios

Thanks Jim

I did not go all the way to 50Mhz.  You comment indicated a knee at 21 Mhz,
I did not see that.  I saw a linear rise in SWR with frequency.  At 28Mhx,
the resistive component was still close to 50 ohms.  It looks like a fixed
inductance or capacitance that likely could be compensated away if I were so
motivated.

FWIW - their website only provides specifications up to 30 Mhz.   It is
possible that the design scope did not contemplate 50Mhz use.

With 80db of relay isolation, termination should be moot.  I was just
verifying that it was. I saw no difference in a 50 ohm load  or an open.  In
my use case, the unused port will be grounded (I think) so I wanted to be
sure.

They should be fine for my use case, but I can see why they did not work for
you.

I feel better knowing I was not missing anything in my measurements.

Tom



-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
Behalf Of Jim Brown
Sent: Monday, March 18, 2019 4:54 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Using Elecraft KPA-1500 for 2 radios

On 3/18/2019 2:38 PM, Tom Georgens wrote:
> Admittedly 1.15:1 is not world class, and could be better, but I don't
consider it unacceptable and I plan on using the switches I bought.  Are we
drawing different conclusions from the same data?

Hi Tom,

Yes, we are. I was using a pair of them to switch inputs and outputs of a
KPA500 an Ten Tec Titan. I use the KPA mostly on 6M, and what you saw on 10M
was significantly worse there.

Another important point. It is totally unrealistic to terminate un-used
ports for isolation measurements, because un-used ports are often not
matched at the frequency where isolation is of concern. I measure isolation
between ports with a VNA (the DG8SAQ VNWA3e). In the case of this unit, I
would measure between the two outputs.

73, Jim

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