The trick here is to ensure that the relay lever springs have some follow.
That is when the contacts make there is a little bit of additional lever
spring travel that provides a self cleaning action. This wiping action is
important on both the make and break sides of a double pole relay.
I have had a homebrew relay switch box, equipped with Radio Shack 10a
relays, in use for 8 years. All bands, 1500 watts. I have destroyed relays
in the box but only when I have had antenna problems. And I have observed
oxidation on relay contacts during receive but that went away when I
corrected the lever spring follow.
Ohms law says you may have as much as 370 vrms and 7.3a while running 1500
watts from a 50 ohm source into a 2:1 missmatch.
de Paul, W8AEF
your smileage may vary.
----- Original Message -----
From: "Doug Faunt N6TQS +1-510-655-8604" <faunt@panix.com>
To: <jirka@jimaz.cz>
Cc: <towertalk@contesting.com>
Sent: Tuesday, February 25, 2003 6:16 PM
Subject: Re: [TowerTalk] Relays
To: <towertalk@contesting.com>
> Date: Tue, 25 Feb 2003 18:45:56 +0100
> From: =?windows-1252?Q?Jir=28=ED_=8Aanda?= <jirka@jimaz.cz>
>
> Hi Mikael,
>
> you have two problems:
>
> 1. - the smaller one - the relay should handle about 7-10A
> 2. - THE MUCH bigger one - the relay should also be capable of
> transfering 0.3 microVolt/50 Ohm - i.e. 0.006 microA . If you start to
> play with this you find that this is THE PROBLEM. Most of the switches
> work fine while on TX but you might be deaf on RX without knowing -
you
> might have 10-30dB atenuation and how to find out, it might be easily
> just the propagation. Just check up WX0B advice on all his gear. "Hot
> switch time to time and the oxide on contacts and might burn out" !?!?
SNIP
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