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Re: Converter Protection



> From:          "Thomas Webb" <tmwebb@ionet.net>
> To:            <amsat-bb@AMSAT.Org>
> Subject:       [amsat-bb] Converter Protection
> Date:          Tue, 5 Dec 2000 07:39:44 -0600

> Having fried a Drake 2.4GHz converter a few months ago, I decided to install
> a Ramsey RFS-1 rf sensing switch to protect any future S-mode converters.
> As a matter of scholarly inquiry, any better ideas floating around out there
> as to protecting mast-mount converters from inadvertent rf?

Dear Tom,

All of us will at sometime transmit into a converter or pre-amp.  One of the
great advantages of being a home brewer is that the repair of your equipment
is usually trival after one of these mistakes.  Been there, smoked it :-)!

In practical terms your best protection is a squencer.  The ARRL 
handbook has an excellent design for one.  I modified mine so when I 
turn on the power for the "S" converter, I disable the two meter rigs PTT.
This took only the addition of a couple of switching diodes as I recall.
Turning on the power also activates the coax relay that switches the
radio from its normal antenna to the converter output.

So far this has worked perfectly.

Another idea I have seen is to use a MMIC amp stage in line with the
converter as a sort of RF fuse.  In other words, if there is an accident,
you burn out the $1.50 MMIC (like a ERA-1 or MAR-1, etc) instead of
the expensive guts of your converter.
> 

> Tom Webb, WA9AFM/5
> 
--73-- David WA0AUQ

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