Tom,
What would be a better choice for a stack match?
I'm quite sure that in the heat of a contest these things have been hot
switched on rare occasion with 1500w. There was one time when I intentionally
hot switched one of them with 100w because I thought the receive signal was
down 10dB or so. Problem went away. Anyway I've been using them for about 6
years or so and only had one that failed after a big lightening strike.
Stan, K5GO
Sent from my iPad
On Oct 10, 2014, at 7:29 AM, Tom W8JI <w8ji@w8ji.com> wrote:
>> I have built four or five "stack matches" using these relays and have been
>> quite pleased with them.
>>
>> http://www.mouser.com/ProductDetail/TE-Connectivity/T92S11D22-12/?qs=%2fha2pyFadujQKxyiQ9QJsU9gOmzykpctnwthD3xoZjoJPHbNrun4hw%3d%3d
>>
>> 73...Stan, K5GO
>
> If you look at the contact material, it is the wrong material type for our
> applications. Those relays are hot switch relays for high current
> applications with Silver Cadmium Oxide. From an engineering bulletin on
> selecting relay contact materials:
>
> Silver Cadmium Oxide
>
> Silver cadmium oxide contacts have long been used for switching loads
>
> that produce a high energy arc. Silver cadmium oxide contacts are less
>
> electrically conductive than fine silver contacts, but have superior
>
> resistance to material transfer and material loss due to arcing. They do
>
> exhibit greater interface resistance between mated contacts, and also a
>
> slightly greater contact assembly heat rise. The minimum arc voltagerating
>
> of silver cadmium oxide is 10 volts and, like fine silver contacts, the silver
>
> in this alloy will oxidize and sulfidate. Therefore, an arc is necessary to
>
> keep these contacts clean.
>
>
> This doesn't mean they won't work and will go up in smoke. It does mean they
> are subject to contact sulfidation which causes intermittent receive. They
> have silver, a hard base material, and large contact area that does not wipe
> well. They also are the type of relay that is subject to contact derating
> from skin effect because of constant resistivity.
>
>
> 73 Tom
>
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