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Re: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30 MHz

To: "RCARIELLO" <>,"Jim Lux" <>,"Towertalk" <>
Subject: Re: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30 MHz
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Wed, 5 Jan 2005 14:40:30 -0500
List-post: <>
Hi Rich,

If the wiring is what it sounds like to me, you are really
setting yourself up to eventually seriously damage your

> Two relays mounted next to each other in an aluminum box.
No shielding
> between the relays. Both normally open. Connect one
terminal from each relay
> together and to an SO-239 connector feeding outside the
box to a 50 ohm
> dummy load.

What happens if one relay sticks and does move, has an open
coil and doesn't move, or a wire breaks? What happens if you
get a short someplace? What happens if a contact welds?

Look carefully at your contact wiring. If there is ever a
possibility a relay or electrical failure can cause two
radios to connect to one antenna port, I'd strongly suggest
you buy different relays!!

If you intend to build a crossover switch, you should at the
very minimum use a DPDT relay that has a reliable armature
that is always synchronized.

73 Tom


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