[Elecraft] KPA500/KAT500 paired with AL-1500?

[Jim Brown]

Hi Jim,

I'm doing exactly that, but with a Ten Tec Titan 425 rather than the 
1500. My method is pretty simple -- I'm using two of W2VJN's 1x2 Top Ten 
relay boxes, one at the inputs, the other at the outputs. They work 
well, except that the SWR is pretty poor on 6M (and is starting to rise 
on 10M) because these boxes use the chassis as the signal return rather 
than carrying it on the circuit board.  To clarify, only a single wire 
goes from each coax connector to the circuit board. And even if the 
shield was carried, the return layer is broken on the return layer.

I put a "band-aid" on the SWR problem by adding the return path, and by 
adding a small stub on the output of the switch on the KPA500 side.  To 
add the return path, you need to run a short piece of braid from each 
coax connector to the circuit board near where the center conductor is 
terminated, and add short sections of braid across the board following 
the signal path from input to each of the outputs. That reduces the SWR 
by half, the stub finishes it off.

Other vendors make similar boxes, but I haven't seen them, so I don't 
know if they do the signal return correctly or not. I don't recall the 
exact length of the stub, but I think I recall that the alternative was 
a cap of about 11 pF.

73, Jim K9YC

On Sat,10/22/2016 4:12 PM, Jim Miller wrote:
> I'm considering adding a bigger amp to the shack. I'd like to continue to
> use the KPA/KAT combo for quick hits and the bigger amp if/when needed. So
> I'd like to make it convenient to switch between them.
>
> The people I've talked to so far actually move coax to make the switch. I'd
> like to avoid that.
>
> I'd need to switch the K3s output from the KPA to the AL1500 and obviously
> switch the outputs as well.
>
> Obviously I'd also need to set the non-KPA power out of the K3 to the per
> band power needed by the AL1500. I seldom run 100w so that wouldn't be a
> big deal.
>
> I'd love to hear from anyone who has done this without screwing/unscrewing
> UHF connectors.
>
> Extra credit for idiot proofing. ;-)
>
> 73
>
> jim ab3cv
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