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Re: [TowerTalk] Stack-matching

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Stack-matching
From: "Joe Subich, W4TV" <lists@subich.com>
Date: Tue, 19 Jul 2022 20:24:51 -0400
List-post: <mailto:towertalk@contesting.com>

Jim,

The question wasn't about a transfer switch ... it was about
a stacking switch that would allow the antennas to be fed to
separate rigs when not used as a stack.

73,

   ... Joe, W4TV

On 2022-07-19 8:16 PM, Lux, Jim wrote:
On 7/19/22 4:26 PM, Lux, Jim wrote:
On 7/19/22 3:04 PM, Joe Subich, W4TV wrote:


On 2022-07-19 4:34 PM, Lee Hiers wrote:
>
Does anyone know of a commercial stack-matching box (for 2 antennas)
that will send the unselected antenna to another port?
MicroHAM stack Switch would do that for two or three antennas. AFAIK,
the product has been discontinued.

I believe the Array Solutions Stack Match will do that *with* the
optional external relay.  However, since I don't use those products
I suggest contacting the manufacturer for details.

73,

   ... Joe, W4TV

On 2022-07-19 4:34 PM, Lee Hiers wrote:
Hi all...

Does anyone know of a commercial stack-matching box (for 2 antennas) that
will send the unselected antenna to another port?  As in: I'm using the
high antenna on radio A, and that makes the low antenna available for use
on Radio B.  And vice-versa.

I envision two antenna connections and a stack output and an alternative
output...something along those lines.

I thought I'd seen a commercial product that did this, but I can't find it now.  I'm sure something could be rigged up using external relays (and I'd
love to hear from anyone who's done that as well), but I would like to
evaluate other options.

Thanks,



Some other things to think about are "port to port isolation" and "fail safe" .

You want to structure the switch matrix (e.g. if using SPDT switches) so that the radios are always isolated from eachother.


If all you have is 2 antennas and 2 radios, what you want is a "transfer relay" or, in microwave parlance, a "baseball switch", or for DC motors, a "reversing switch".  It's a DPDT set up to swap paths.

THey're available surplus for moderate powers (and, I suppose high powers), but they're designed so that you never inadvertently have output from Radio A going into Radio B.


here's a fairly beefy vacuum transfer switch.. I can't find a data sheet, but I believe it's rated for kilowatts.  what you'd also want to know is the isolation.  60 dB isolation with a kW on one path would be 1 mW on the other path, which probably won't blow up your receiver.

https://mgs4u.com/product/rly-lc-01/


fwiw the transco 700C70400 on the mgs4u website is only rated for 20W. You see a lot of those and similar ones surplus.

here's a test report from 1972 (back when Deep Space Network was still called Deep Space Instrumentation Facility) on a bunch of different models:

https://ipnpr.jpl.nasa.gov/progress_report2/XI/XIW.PDF

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