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

[Jim Lux <jimlux@earthlink.net>]

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 


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