Bill,
Remember that the two most common "verticals", the R-7 by Cushcraft and the
DX-77 by Hy-gain are not 1/4 wave verticals. The R-7 is a halfwave vertical
and the DX-77 is a hybrid windom fed 1/2 wave vertical.
Both antennas work quite well IF they are elevated to minimize ground
losses. I have found the R-7 and DX-77 to be excellent performers when
elevated at least 1/4 wl above ground, or even better 1/2 wave above ground
on their lowest cut frequency. That's about 66' for the R-7. I read
W4RNL's piece to say that the radials made a difference of less than 1Db
over poor ground diminishing as the existing ground improved (less lossy).
That was for vertical dipoles that were virtually groundmounted.
Both the R-7 and the DX-77 use a counterpoise to minimize ground losses, not
eliminate them. I would love to see a direct comparison of the 1/2 wave
verticals. I have done rather extensive on-the-air comparisons of the R-7
and the DX-77 as compared to a tribander and a dipole, but the antennas were
all mounted above 150' in one test and above 240' in the other so they won't
track most installations. I did find that the vertical often gave me better
DX take-offs than the dipole and on some occasions than the tribanders. I
expect that was due mostly to polarization. I, for one, think they are
pretty good antennas for what they are. Simple to install and small real
estate requirements providing you can them up at least 33' in the air. A
push-up mast works pretty well.
Jon Hamlet, W4ZW
Casey Key Island, Florida
"A little bit of paradise in the Gulf of Mexico"
>he is writing about VERTICAL
> DIPOLES, not
> the common 1/4 wave vertical. One of the big questions recently has been
> about the validity of the manufacturers claims that their particular
> vertical does not need radials- There has been LOTS of talk about
> the need,
> and the claim that the DIPOLES do not need radials.
>
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|