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From: Ralph Mowery <rmowery42@charter.net>
Newsgroups: sci.electronics.design
Subject: Re: Sleeve dipoles
Date: Mon, 23 Dec 2024 15:02:04 -0500
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In article <1r5178a.10eyjis13gf62kN%liz@poppyrecords.invalid.invalid>, 
liz@poppyrecords.invalid.invalid says...
> 
> > The bottom  dipole half is never grounded. Another name is coaxial
> >  antenna. Usually you find them in marine application because of
> >  the counter poise. 
> 
> Suppose the feed point had a 1:1 isolation transformer, there would be
> no reason why the dipole couldn't be grounded at any point alog its
> length.  The same isolatio could be achieved by a quarter-wave line.
> 
> 
> 

The bottom half can not be grounded no matter what except at the feed 
point maybe.  The sleve dipoe can be thought of as a ground plane with 
the elements just folded all the way down instead of down at a 45 deg 
angle that makes the impedance near 50 ohms.  It is usually mounted with 
a mast that goes to the feed point and it can be either a conductor or 
nonconductor.  This pipe can then be fastened to a conductor or 
nonconductor.

While a coax dipole can be made of a coax cable with the braid just 
folded back over the outer insulation it may not work very well due to 
the closness of the brade and the quality of the insulation.