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

To: "OM7ZZ, Jozef Urban" <>,
Subject: RE: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30
From: Jim Lux <>
Date: Wed, 05 Jan 2005 15:44:43 -0800
List-post: <>
At 02:38 PM 1/5/2005, OM7ZZ, Jozef Urban wrote:
We're builded 10 ANT / 2 Radio switch with Gigavac G2SP relays. On each ANT port are three of them used.
Achieved -60dB isolations on adjacent ANT ports and more than -70dB on non adjacent ports.
When both radios would like to select the same antenna, isolation is still around -68dB.
All mentioned isolations was measured at 28MHz.

Some fotos and measurements are here:
Insertion loss
Isolations same ANT port
Isolations adjacent ANT ports
Isolations non-adjacent ANT ports

73 Jozef OM7ZZ

Looks real nice. I assume you're using the little blue relays to switch the current for the RF relay coils?

It looks like you have 3 SPDT relays on each antenna port. The first relay connects the antenna to one of two other relays. The side you're connecting to is switched to the radio. The "other side" is switched to ground?

So, the isolation from one radio to another would be essentially two relays worth.

Is the copper strip "star" in the middle designed as a 50 ohm microstripline? Or is it just a convenient size?

Jim, W6RMK


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