[TowerTalk] Switching relay ratings

[Scott Bullock]

NTE makes a 10amp at 250v relay with a 12 vdc coil, use it here with a homebrew 80 meter butternut phasing box and they work excellent. Contacts are around 1/4" in diameter, so they can handle as much rf as you can throw at them.

Scott

N1CX



At 07:11 PM 1/30/00 +0000, you wrote:

>

>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 

>

>Don't forget to update your entry on the World Contest Station Database, at

>http://206.102.70.3/search.htm

>

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>

>

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