[TowerTalk] Stack-matching

[Lux, Jim]

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