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Re: Topband: Operating with separate TX and RX antennas

To: "Brian Machesney" <>, <>
Subject: Re: Topband: Operating with separate TX and RX antennas
From: "K9AY" <>
Date: Mon, 5 May 2008 13:51:40 -0500
List-post: <">>
>From Brian K1LI,

>> I read a lot about flags being sensitive to nearby objects...

A minor clarification -- it's not that these antennas are sensitive, but 
that they are usually installed at limited-size QTHs and end up close to the 
TX antenna.

>> ... and I know how to de-tune those objects, but my question is this: if 
>> the object to be detuned is my TX antenna, don't I have to switch the 
>> "detuner" in when I'm on RX and switch it back out when I'm on TX?

Yes, the detuning is switched into place during receive, but first check to 
see whether the TX antenna actually needs detuning or not. Some dipoles, 
inverted-Ls and other wire antennas have been effectively detuned by opening 
the T/R relay in the rig or amp. This depends on the antenna impedance, 
feedline length, tuner, and anything else in line. It's worth checking 
before starting the detuning work.

A shunt-fed tower will almost certainly require detuning. Of course, any 
other nearby tower (not fed) with enough height to be an effective 
re-radiator at 160M can have a fixed detuning network.

73, Gary

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