Mike: I apologize if my query came across as an insult!! Mea culpa sent from
out here in the black hole of 160 meter communications - s/w Utah.
I think I said I wasn't doubting your claim and I wasn't questioning your
"conclusions" - just attempting to find some modeling or Measures of
Performance to substantiate it as, lately, I have been seeing/reading of
anecdotal "evidence" and I, for one, am interested in supporting
data/measurements.
I use/employ a 43' vertical on 160 through 17 but can't compare it to a 1/4
wave over the same radial field -- certainly your closeness to the water may
"answer" or provide a reason for your success with a 5/8 over 1/4 so, with the
modeling info I supplied perhaps someone who knows the modeling apps(s) could
do some "investigating" in the form of modeling to answer that?!?~!
OK?? 72, Jim R. K9JWV
> From: armstrmj@aol.com
> Date: Sun, 8 Sep 2013 07:18:18 -0700
> To: w8ji@w8ji.com
> CC: topband@contesting.com; rodenkirch_llc@msn.com
> Subject: Re: Topband: 5/8 wavelength vertical is mo betta than shorter
> versions??
>
> Tom (and James),
> I am well aware that my comments concerning the 5/8ths wave was based upon
> subjective/anecdotal evidence. I am in a science (Astrophysics) by
> profession..... I do know the difference. HOWEVER, I cannot completely throw
> out the simple fact that when I altered my 20 meter omni antenna for Winlink
> to the 5/8ths, that I received UNSOLICITED comments from the system users
> stating (100 percent of them) that my signal was much improved into the areas
> they happened to be sailing. None of those people, not a single one, knew
> that I was changing my antenna. The purpose being just that..... to see if
> anyone complained or said anything else concerning performance from THEIR
> point of view. In reality, THAT is the point when supplying a service.....
> What do the USERS think of the performance, not what I think or what a FS
> meter says.
>
> Even if I had the equipment to measure the performance and the equipment says
> that my signal should be improved, but the Winlink user comes online and
> universally states my signal sucks, I will REMOVE that antenna. I know that
> isn't likely, but if the modelling software states the signals should be
> worse and they are, 100 percent, reported as improved, then there is
> something at play that the modelling software isn't taking into
> account........
>
> Not arguing, just answering that initial question that from my EXPERIENCE
> with that antenna, it works better than the quarter wave at the same
> locations I happen to be...... AND ONLY ON 20 meters. I won't speak to any
> other band, although I would think it would work there, too, because I have
> not put one up for those other bands.
>
> As an aside, alot of folks are using that so-called non-resonant vertical
> antenna that is roughly 43 feet tall....... They seem to be having some
> success with them on the bands. Physically, they are pretty convenient.....
> and on 20 meters, they happen to perform pretty well, judging from user
> comments, anyway..... and at that band, it is roughly 5/8 wave in electrical
> height. So, again, I find it interesting that actual experience argues with
> the modelling software (in MY particular instance). But, again, in my case
> IN HAWAII, I had an outstanding location that, for some reason I don't know,
> happened to favor the 5/8 by alot more than even the theoretical gain would
> indicate. NOBODY would comment, much less 100 percent of commentors, on a
> slight gain of 2 db. Heck, that wouldn't be worth the effort. However, I
> think you are quite right, Tom..... something else is at play.... ground
> clutter (I had some.... loads of tropical trees and plants in the area), some
> significa
nt
> ly tall sailboat masts RIGHT ACROSS THE STREET from my house (very close),
> etc, etc. Then you consider the seawater ground that was so close by......
> There are many factors to take into account, not much of which does a
> modelling software take into account. Undoubtedly the answer is there and
> not directly related to antenna gain. I did try elevating it on top of a 40
> foot pipe mast and using 8 resonant radials....... it made no difference
> except to increase the chances that high winds would knock it down. In terms
> of SUBJECTIVE performance and comments, no difference. So, I put it back on
> the ground and carried on.
>
> Remembering what the antenna was for, and where it was located, putting up a
> horizontal 80 or 90 feet in height simply wasn't possible. The SERVICE I was
> providing required OMNI directional capability, so even a dipole would be
> unsat in at least 2 directions...... those being the directions an emergency
> call would not be heard...... Not a good situation for the given purpose,
> right?
>
> I will say that I didn't appreciate the comment concerning how I came to my
> conclusions about antenna performance. Insults only prove that one has run
> out of reasonable arguments..... and that is ALL it proves. Given that, this
> will be my last post here and I am likely removing myself from the list.
> Insults are NEVER science...... not now, not ever!
>
> Mike AB7ZU
>
> Kuhi no ka lima, hele no ka maka
>
> On Sep 7, 2013, at 18:59, "Tom W8JI" <w8ji@w8ji.com> wrote:
>
> >> The above modeling results just don't support that contention/posit so I'm
> >> wondering what else comes in to play that could lead folks to love the 5/8
> >> wavelength vertical over a shorter version, regardless of frequency? I
> >> don't see one performance comparison that supports that claim. I'm not
> >> saying the "claiming person" isn't correct but....I don't see how!
> >> Help - what am I missing here?
> >> 72, Jim Rodenkirch K9JWV
> >
> > The 5/8th wave obtains the small amount of gain it has through effects of
> > ground reflection. The current maximum is elevated, and that elevation
> > causes additional phase shift with the illumination of earth out some
> > distance from the antenna. The re-radiation of earth is sometimes explained
> > by an "image antenna". The image antenna is a fictitious antenna directly
> > below the real antenna, and this "image antenna" simply represents what the
> > earth at a distance does from the illumination from the main antenna.
> >
> > The 5/8th wave moves the current maximum slightly higher than a quarter
> > wave above earth, so the fictitious image moves slightly lower than a 1/4
> > wave below surface.
> >
> > If you move the 5/8th wave above earth, such as in a groundplane well above
> > the earth, the extra length no longer provides gain. Instead, it actually
> > reduces gain at low angles.
> >
> > Another effect is the extra height above ground of the high current area
> > can help get the antenna's main radiating area a little bit higher above
> > ground clutter.
> >
> > This would also apply to an extended double zepp, where the second antenna
> > half makes the image unnecessary. Each half of the double zepp is the image
> > of the other side, so we don't need earth.
> >
> > So it is a very specific benefit from the 5/8th wave caused by moving the
> > current height up above a reflecting surface, or in the case of a double
> > zepp moving current away from a second identical element while still having
> > a common center feedpoint.
> >
> > One of the biggest antenna hoaxes played on people was the 5/8th wave CB
> > groundplane antenna. Two meter 5/8th wave groundplanes are the same. The
> > work on the broadcast band to increase groundwave signal because soil is
> > often reasonably low loss on the AM BCB. If the soil out some distance from
> > the antenna is lossy, or if it does not exist, the 5/8th length causes
> > increased low angle loss.
> >
> > This is why when you look at models, outside of specific cases like some
> > cases of low broadcast band use, we have a tough time seeing the gain
> > imagined or claimed. A field strength meter has an equally difficult time.
> > :)
> >
> > 73 Tom
> > _________________
> > Topband Reflector
> _________________
> Topband Reflector
_________________
Topband Reflector
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