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Re: sequencer switching



----- Original Message -----
From: <w7lrd@comcast.net>
To: "NW VHF" <PNWVHFS@googlegroups.com>
Cc: "AMSAT-BB" <AMSAT-BB@amsat.org>
Sent: Thursday, January 17, 2008 4:50 PM
Subject: [amsat-bb] sequencer switching

> G'morning
> My 1.2Ghz system is progressing nicely.  I am currently working on a
> sequencer for "switching around" my amp.  I have several good quality coax
> relays.  Are some preferred over others?

Hi Bob, W7LRD

Use coax relays with N connectors and the greater isolation in dB between
RX/TX ports and if you don't have this data also called "cross-talk" you can
measure it on spectrum analyser.
Also use relays with the shorter switching time and the higher power
handling capability.
Relays with high isolation between ports have all N connectors fitted in
line in a brass block and relays with very poor isolation have connectors
fitted in a configuration similar to a hammer.

>   A couple I have require reversing polarity to switch them back.  This is
> requiring more circuitry and complexity.  Are these latching relays
> necessary?

They are not necessary for your application and in general they are not
suitable with standard sequencers and in addition they have higher
switching time.

> I'm seeing several relays available on ebay.
> The time spent  in transmit is miniscule compared to receive.
>
> 73 Bob W7LRD
> Seattle
> "if this were easy, everyone would be doing it"

73" de

i8CVS Domenico







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