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

To: Jim Lux <>,
Subject: Re: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30
From: "OM7ZZ, Jozef Urban" <>
Date: Thu, 06 Jan 2005 01:22:41 +0100
List-post: <>
Yes Jim.
Little blue relays are used for switching of power vacuum relays. Principle
is same as used at serialy produced little brothers of this switches -
Double Ten and Double Six. Diagram of one port is available at:
Strip star cannot be at 50ohm because arms to unselected ports creates open
stubs and affects matching. Correct impedance is higher and has been
obtained experimentaly.
-70dB of isolation is a value who can be obtained relative easy with most of
relays suitables for RF switching if two are used in line. As Tom said, very
important is a grounding and proper layout.

73 Jozef OM7ZZ

----- Original Message ----- 
From: "Jim Lux" <>
To: "OM7ZZ, Jozef Urban" <>; <>
Sent: Thursday, January 06, 2005 12:44 AM
Subject: RE: [TowerTalk] Help need Vacuum Relay Isolation 1.8 to 30

> 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
> >adjacent ports.
> >When both radios would like to select the same antenna, isolation is
> >around -68dB.
> >All mentioned isolations was measured at 28MHz.
> >
> >Some fotos and measurements are here:
> >
> >
> >Insertion loss
> >
> >SWR
> >
> >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
> 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
> 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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