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Re: Topband: KD9SV-OK1RR relays ???

To: "MU 4CX250B" <4cx250b@miamioh.edu>, <marcom@centrum.cz>
Subject: Re: Topband: KD9SV-OK1RR relays ???
From: "Tom W8JI" <w8ji@w8ji.com>
Reply-to: Tom W8JI <w8ji@w8ji.com>
Date: Sun, 30 Aug 2015 20:00:33 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
I'm not sure goosing the pull-in voltage is always a good idea. It may
shorten the initial closing time a bit, but (depending on the relay)
it can aggravate contact bounce, doing more harm than good. It also
stresses the relay.


Done properly, it doesn't hurt a thing. The proper way is to use current limiting.

It is safe to run 50 volt supplies on most 12 volt relays, but there is a point of diminishing returns on speed. The high initial voltage ramps up the magnetic field faster, but it does not cause excessive heat or current. This is because the relay starts at near zero mA from inductance.

None of this matters, though. Using a relay on make for protection is a bad idea. The de-active state should be used for protection, and the active energized state used to allow RX.
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