Topband: Help de-coupling the TX antenna

[Guy Olinger, K2AV]

Assuming (bad word, I know) that you are running coax directly to the 
antenna feedpoint, and any matching you do is right at the antenna 
feedpoint...

Check and see if the path of the TX antenna in the Orion is grounded 
or open when you are in receive mode and using a separate RX antenna.

If it is grounded, then make the electrical length of TX feedline from 
the Orion to the antenna feed an odd number of quarter-wavelengths, 
and if open then make it a multiple of a halfwave. The electrical 
length includes going through filters, through your amp in 
non-actuated mode, etc, etc.

This will turn the feedpoint of the antenna into a high impedance 
point and cause the inverted L to become a largely isolated 1/4 wave, 
hence non-resonant.

This procedure can be adapted for more complex circumstances. The idea 
is to let a normal or improvised QSK mechanism cause the antenna end 
of the feed to appear high Z.

Lossy or very long feedlines defeat the mechanism. Some filters can 
defeat it. A variable tuner in-line in the shack would produce 
inconsistent results.

73, Guy

----- Original Message ----- 
From: "Eric Rosenberg" <wd3q at starpower.net>
Subject: Topband: Help de-coupling the TX antenna


> Almost everyone said the tx antenna needed to be de-coupled on RX 
> and
> referred me to ON4UN's book.

> - How do I control this? A seqeuencer of some sort?

> - What happens to QSK? My station is an Orion and Herc II amp.  QSK 
> is
> very nice!