> Thanks, much. It is interesting that, as far as I can recall,
> yours is the first reference (Directly) to the QST article. I
> had forgotten it (Senior moment?) I must go back and re-read.
The radials were added at WWVH after field strength testing showed
that the half wave verticals failed to produce the expected field
strength due to e-field losses in the ground below the bottom end
of the antenna. While the radials did not effect the feed point
impedance they provided a significant improvement in field strength.
> About the radials-- I saw an indirect reference that the
> radial field was an FCC REQUIREMENT. (?)
120 1/2 wave radials are a FCC requirement for AM antennas
irrespective of the height of the radiator - even when the
radiator is in the vicinity of .5 wavelength. The radials
can only be eliminated by showing that an installation is not
possible and/or the required field strength can be obtained
without them.
73,
... Joe, W4TV
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Bill Aycock
> Sent: Monday, April 06, 2009 2:45 PM
> To: Michael Tope
> Cc: towertalk@contesting.com; N7mal; John Geiger; Robert Redmon
> Subject: Re: [TowerTalk] Vertical vs Beam
>
>
> Mike-
> Thanks, much. It is interesting that, as far as I can recall,
> yours is the
> first reference (Directly) to the QST article. I had
> forgotten it (Senior
> moment?) I must go back and re-read.
> About the radials-- I saw an indirect reference that the
> radial field was an
> FCC REQUIREMENT. (?) I am not impressed by the expertise
> shown by the WWV
> web site.
> I still see (in my own mind) confusion in terminology
> concerning the terms,
> 1/2 wave monopole; 1/4 wave vertical with skirt; 1/2 wave
> vertical Dipole;
> etc. I need to check some more in some Handbooks, and maybe
> Kraus. More
> re-reading. It seems to me that calling their antennas "1/2
> wave dipoles"
> is incorrect.
>
> Bill--W4BSG
>
>
> ----- Original Message -----
> From: "Michael Tope" <W4EF@dellroy.com>
> To: "Bill Aycock" <billaycock@centurytel.net>
> Cc: <towertalk@contesting.com>; "N7mal" <n7mal@citlink.net>;
> "John Geiger"
> <aa5jg@yahoo.com>; "Robert Redmon" <k5sm.bob@gmail.com>
> Sent: Monday, April 06, 2009 12:25 PM
> Subject: Re: [TowerTalk] Vertical vs Beam
>
>
> > Bill Aycock wrote:
> >
> >> As far as the subject of 1/2 wave verticals goes, the WWV
> site leaves
> >> out a LOT! 1. Where is the feed point?
> >
> > The upper 1/4 wave of the 1/2 wave monopole is insulated.
> The antenna
> > is fed with coax at this point against the skirt wires. This is
> > described in the QST article and can be scene in the
> picture link of
> > the WWVH antenna that W4TV posted.
> >
> >> 2. what is the feed point impedance?
> >
> > The article says 50 ohms.
> >
> >> 3. Are the lower ends of the "guys" grounded?
> >
> > No, the article indicates they are insulated
> >
> >> 4. Why is it important that the Coax feeds do not cross?
> >
> > Makes for a neat installation, but I can't imagine that it
> makes any
> > difference to performance whatsoever.
> >
> >> Does anyone know?
> >> Are the arrangements of the TTers with 1/2 wave verticals
> like WWV,
> >> and if not, why reference it?
> >
> > Probably not exactly, Bill. I thought the point in the article QST
> > where they mentioned the ground radials not impacting feedpoint
> > impedance somewhat paralleled N3OX's experience. The article also
> > mentions the expected gain over a 1/4 wave monopole (1.7dB).
> >
> > One interesting thing is that per the picture link that
> W4TV posted,
> > they elected to use ground radials in the WWVH
> installation, but they
> > did not in the WWV installation (the QST article claims
> that when it
> > was determined tha the radials didn't effect input impedance it was
> > decided not to include them in the installation). Perhaps
> radials were
> > added later at WWV (my understanding is that they were only
> included
> > for the two backup broadband monopoles antennas). I would be
> > interested if anyone can confirm this. This speaks to previous
> > discussions as to what field strength benefit is derived by
> including
> > radials under a 1/2 wave vertical dipole.
> >
> > 73, Mike W4EF...........................
> >
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> >
>
>
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