Sam, several years ago I started doing relay switching for automation of
band changes etc. At the time I had a 4x811A amp so (optimistically) was
aiming for the kilowatt power handling ability (really that amp was lucky
to put out 650W).
I had looked at what commercial or published article products use and many
of them use PCB mount relays rated for 10-15 Amps. An example would be
AC0HB's article in March/April 2014 QEX. He uses Omron G6RN-1-DC12 PCB
relays and he was specifying for 1000W power handling ability using these
nominal 8A contacts. These relays are very affordable (just $3 or less). I
tried these relays and it was a complete disaster for me. Just a few weeks
into RTTY contest season, the relays were failing and prying them open they
all had extreme discoloration from overheating. It was clear that the
high-bands (e.g. 15M) were suffering far more damage than the low bands
(e.g. 80M). I think this indicates that the internal structures while they
might be sized for 8A at DC or 60Hz, are not sized for the same current at
21MHz. In retrospect, I should have realized that even the tiny PCB pins on
them were simply not up to snuff for high duty cycle RTTY contesting.
However these relays, I do believe are good for 100W power range.
What I ended up using was much beefier relays. I went to Struthers Dunn
(now P&B) DPDT T92 relays with paralleled 30A contacts. I got a bigger
legal-limit amp and have been COMPLETEY happy with these at legal limit.
Over a hundred thousand QSO's through these new relays without a problem.
These are the "low impedance" side of my tuner switching.
For the high-impedance (ladder line) side of my switching, I use open-frame
relays with the contacts pried a little further apart than stock. Example
part is the McMaster Carr 7384K14. N6RK outlines the process of widening
the contacts in the May 2009 QST Hints and Kinks.
Now with any of these Silver contact relays you will have to "clean" them
occasionally with either transmit power or (if a RX-only contact) an
external voltage source of 12V or more, to blow them clean. W8JI has a good
procedure here in his "electrical cleaning" section:
https://www.w8ji.com/relay_cleaning_and_life.htm
Tim N3QE
On Thu, Dec 6, 2018 at 11:48 AM Sam Josuweit <samjos@epix.net> wrote:
> Can anyone recommend a good general use relay for antenna switching in the
> 800-1000w power range? I know using power relays can be a roll of the dice.
>
> According to modeling peak voltages should be less than 450V.
>
>
>
> Thanks
>
> Sam(N3XZ)
>
>
>
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