[Elecraft] KPA500 switching ideas with a Flex-5000A?

[Joe Subich, W4TV]

 > This seems awfully expensive.

It is - but the Totsu DPDT coaxial or other transfer relays are
an off the shelf solution.  The Totsu solution can be simplified
to two relays by careful choice if cable lengths and adding a
couple compensating stubs in the "amplifier" leg.

One can certainly spend a lot less if he is willing (and has the
ability) to design strip line circuit boards for off the shelf
relays.  This isn't an application where one can simply take
three DPDT or six SPDT "power" relays, nail them to a breadboard
and solder random lengths of #14 wire between the appropriate
terminals.

73,

    ... Joe, W4TV


On 7/14/2011 10:40 AM, Dick Dievendorff wrote:
> This seems awfully expensive.
>
> Array Solutions doesn't spend that much for the relays inside their Six Pak.
>
> Top Ten devices doesn't spend that much for the SPDT relay inside their A/B
> station selector.  That unit goes for $77, and that includes a nice box and
> the connectors.
>
> The T/R switch within my Ameritron AL-1200 doesn't cost that much.
>
> Wouldn't a sealed or frame relay do the job?  600 watts into a 50 ohm
> resistive load is 12 Amps.  20A DPDT frame relays can be acquired for a lot
> less than a coaxial relay.
>
> SPST relays cost even less.  KK1L uses relays that are advertised at about
> $3.16 each in his 2 x 6 antenna switch.
>
> Is it necessary to operate concurrently on HF and 6 meters?  Wouldn't a
> couple of SPST relays suffice for this application?
>
> 100 watts into 50 ohms is 2A. You can use a much smaller relay on the 100
> watt exciter to amplifier side. I'd use 5A relay.
>
> 73 de Dick, K6KR
>
>
>> That can be accomplished with three DPDT coaxial relays such as the CX800M
> ($159/ea from http://www.rfparts.com/coaxial.html ) $477 total
>
>> It can be done with two coaxial transfer switches but probably cost more
> (KC 1420-820 from
> http://www.surplussales.com/Relays/rfcoaxialrelays/rfcoax_n.html
>
> are $275/ea. ($550 total)
>
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