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[TowerTalk] Relays

To: <>
Subject: [TowerTalk] Relays
From: (Paul Playford)
Date: Wed Feb 26 10:24:17 2003
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" <>
To: <>
Cc: <>
Sent: Tuesday, February 25, 2003 6:16 PM
Subject: Re: [TowerTalk] Relays

To: <>
>    Date: Tue, 25 Feb 2003 18:45:56 +0100
>    From: =?windows-1252?Q?Jir=28=ED_=8Aanda?= <>
>    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  -
>    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" !?!?


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