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

2002年8月18日 13:10:35 -0700

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]