The FES (front-end-saver) does exactly you are suggesting it should do.
When the rig is keyed the receive antenna is disconnected, the receive port
is shorted to ground and I also provide an additional two keying relays for
a linear amplifier. Which one is in use depends on whether your rig is QSK
or an older non-QSK type ie SB220 etc.
E-mail me direct for any more information. de gary, kd9sv
----- Original Message -----
From: "EUGENE SMAR" <spelunk.sueno@prodigy.net>
To: "DF2PY" <df2py@t-online.de>; <topband@contesting.com>
Sent: Monday, September 09, 2002 10:22 PM
Subject: Re: Topband: front end protection
> 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>
To: <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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