[TowerTalk] Switching relay ratings

[Pete Smith]

I have a 4-element lazy-vee array for 80 meters which uses a homebrew
switching system to switch both the shields and center conductors of the 4
feedlines.  I'm sending +DC, -DC and AC to the box to do this, like the
cable-less antenna switches do.  

I used 4 DPDT 12V-coil relays with contacts rated 10 A @125 VAC.  I run
~1200 watts output on 80.  The array is cut for CW, and SWRs there are
~1.2:1.  However, I experimentally discovered that I could run the array in
the 75m DX window as well, even though the indicated SWR is over 3:1.  My
aplifier can tune out that much mismatch (barely) and the array performance
is still quite good.

However .... after a couple of years, the relays are failing.  Actually,
the SE position (2 sets of relay contacts in series actuated at the same
time) went first, but now even NE (no relays actuated) is acting flakey on
receive (intermittent loss of gain, corrected by a quick shot of rf through
the feedline, but recurs after a while).

I'm going to have to rebuild the box, and I'm wondering whether to go to
beefier relays.  Is there a way to calculate whether the 10A rating should
be adequate, at least for the end of the band where the match is good?
Bottom line, is it the use into a high SWR that is probably responsible for
the relay failures?  Should I resign myself to not using the array on
phone, unless and until I can figure out a way to make it match up there
too?  

73, Pete Smith N4ZR
n4zr@contesting.com 

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