[TowerTalk] 4 square switching relays

jimlux jimlux at earthlink.net
Fri Mar 27 06:34:44 PDT 2009

Pete Smith wrote:
> At 09:39 AM 3/26/2009, jimlux wrote:
>> I think what makers of such boxes do is buy a few relays, build some 
>> boxes, sell them, and see what the market tells them.  If the first 
>> few customers complain about the relays failing, they find another 
>> kind of relay, build new boxes, send em out, etc.  (or, the first 
>> boxes are being built for a buddy, or a semicustom sort of installation).
> I know this was not the case at TopTen.  George, W2VJN described the 
> testing process he used to make sure the relays they use can do the 
> job.  IIRC, it included extended key-down tests as maximum legal power 
> and more, into a relatively high SWR.  You can probably find his message 
> fairly easily if you search the archive of this list for his callsign 
> and simply the word relay.
> 73, Pete N4ZR
Pete's right.. I should have said "some" makers..

But I did search and the only thing I turned up is the following post 
(from Pete)
On the other hand, TopTen has used very inexpensive DPDT relays in its
1500-watt remote relay switchboxes for a decade or more.  They are
Panasonic brand JW1FSN-DC12V (12V coil), priced at 2-05 in onesies in the
latest Mouser.  I recall George W2VJN recounting lengthy key-down tests
with up to a 3:1 SWR, and I'm sure if failures were common we would have
heard about it, from RTTY contesters in particular.


The question I would have is whether key-down tests are really a 
complete test campaign. They essentially tests power handling, but the 
other things that have been mentioned (capacitive coupling to the coil, 
insulation failure, isolation, small signal handling, electromechanical 
life) are all things that would be addressed in a full manufacturing 
life test.

And, the "if failures were common we'd have heard about it" is basically 
the "let the first users be life testers" strategy.  I suspect a lot of 
ham products start out as a "hey, I need a X Widget, can you make one" 
or "I needed an X Widget, so I made one", and then someone else wants 
one, and eventually, it turns into a business.  And the ham market is 
somewhat unique in that it will tolerate less rigorous testing and 
durability in exchange for lower cost.. otherwise, hams would be buying 
their relay boxes from DowKey or similar firms, who would be happy to 
sell you any kind of high power switch matrix you want guaranteed for a 
million operations, for a price.

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