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:
http://www.microham.com/double%20ten%20switch%20features.html
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" <jimlux@earthlink.net>
To: "OM7ZZ, Jozef Urban" <om7zz@stonline.sk>; <towertalk@contesting.com>
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
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:
> >www.microham.com/Custom/DT/doubleten1.jpg
> >www.microham.com/Custom/DT/doubleten2.jpg
> >Insertion loss
> >www.microham.com/Custom/DT/insertion.jpg
> >SWR
> >www.microham.com/Custom/DT/swr.jpg
> >Isolations same ANT port
> >www.microham.com/Custom/DT/isolation1.jpg
> >Isolations adjacent ANT ports
> >www.microham.com/Custom/DT/isolation2.jpg
> >Isolations non-adjacent ANT ports
> >www.microham.com/Custom/DT/isolation3.jpg
> >
> >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
>
>
-=x=-
Skontrolované antivírovým programom NOD32
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