Topband: front end protection

[EUGENE SMAR]

Folks:

     Wolf's idea sounds like it would make a good product (Are you
listening, Gary KD9SV?)  Merely switch the RX-only antennas during receive
by using the rig's SEND line, or equivalent.  Disable the relay power if you
wish to receive on the TX antenna.  There could also be a second set of
contacts to short out the RX input JIC (Just In Case) and/or to switch a
linear - the original purpose for the rig's SEND contacts.

     Gary's DXpedition version of his front-end saver looks like it would be
the Swiss Army Knife for Topband RX antenna filtering, amplification,
switching and protection, if this switching feature were to be added.  No
need to dig into a rig to add RX-only inputs, plus one would get protection
as well.

73 de
Gene Smar  AD3F
-----Original Message-----
From: DF2PY <df2py@t-online.de>
To: topband@contesting.com <topband@contesting.com>
Date: Monday, September 09, 2002 10:11 PM
Subject: Topband: front end protection


hello reflectees !

The problem of protecting the rx front end while transmitting is a simple
one.
Its very important NOT to use an extra RX jack (which most Radios have these
days)for beverage connection, You may create a loop on the backside of the
radio
as You have in this case two lines of considerable length attached to
it.Needles
to say that the RF potential will be different for both lines and
compensating
currents flow thru the radio.And if switching this RX input fails for
whatever
reason- the RX goes to smoke in a jiffy. Foolproof design is, to use only
the
main TX/RX jack and to switch it via the PTT for the RX -mode into
filters/preamplifiers etc etc.If the switching in this design fails, You
simply
replace the external preamp transistor and thats it. Mostly a "one Dollar
affair".
I built it this way and never had a failure in a many years.
   73 de wolf  -df2py-

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