[Antennas] 1/4 WL verticals w/radials vs. 1/2 WL Verticals fed 'off-center'

Sun, 18 Aug 2002 20:38:37 -0700

As documented on my web site,
my experiments showed that a
30 foot vertical on 20 meters
with no radials is indistinguishable
from a 16 foot vertical with
32 half wave radials.

Rick Karlquist    N6RK
[email protected]
www.n6rk.com
www.karlquist.com

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Jim Shaw
> Sent: Sunday, August 18, 2002 1:11 PM
> To: [email protected]
> Subject: [Antennas] 1/4 WL verticals w/radials vs. 1/2 WL
> Verticals fed
> 'off-center'
>
>
> I found George's summary of the requirement for the classic
> 1/4 WL vertical
> to have radials to be an excellent recap.  Thanks George
> for refreshing my
> memory.
>
> However, there are now several commercially available
> variants of the
> 'vertical dipole' which are touted as verticals not needing
> radials.  Some
> designs, like several offered by Force-12 among others, are
> center-fed,
> physically shortened, half wave length (dipole) radiators
> that are mounted
> vertically.  Logically, vertically mounted dipoles
> shouldn't need radials to
> operate properly since a horizontally mounted dipole does
> just fine without
> radials.
>
> Other 'no radials' verticals, like the AV series offered by
> Hy-Gain, or the
> "R8" offered by Cushcraft, seem to be 'vertical half wave'
> radiators, like
> the vertical dipole, but have the added twist of not being
> center-fed.  In
> addition, instead of both sides of the feed point utilizing
> physically
> identical radiators, they use a 'counterpoise' to act as
> the radiator on the
> 'shortened' side of the 'half wave'.
>
> I would greatly appreciate a short recap of the theory and
> practice relating
> to the need for radials like these newer so-called '1/2 WL'
> verticals.
> Especially as it relates to some of the ones claiming to be
> fed 'off-center'
> while also using 'shortened' radials or a 'counterpoise'.
>
> This 'half wave' design is particularly confusing to me since I have
> reviewed my copy of the K7LXC's report entitled "HF
> Vertical Performance
> Test Methods and Results"
(http://www.championradio.com/forsale/ ).  Based
upon my reading that report, it is easy to conclude that the 'no
radials'
Cushcraft R8 multiband 1/2 WL vertical is as good, if not better, than
the
classic '1/4 WL plus radials' designs offered by Butternut,
Newtronics, and
others.

Comments??

73 de Jim [email protected]

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