What the model DOES predict is that the dipole has a weakness at very
low arrival angles that the vertical does not. The model *AND* your
comparisons tell me that stuff is likely coming in at very low angles.
Or in some currently unexplained mode that favors vertical
polarization.
Without knowing the incoming angles (measured, not predicted) the
answer as to which would work better would have been left as
unanswered until dipole was put up there and A/B comparisons done. At
your place I could suspect the vertical would shine, at least because
I know you have a commercial broadcast grade ground system under it.
The dipole could not possibly beat it at the lower angles. Not in my
modeling programs. For W8JI I use the mininec ground, because it's not
telling a lie there.
This still seems to be applicable on 80 meters for a scaled version of
the same problem, with much anecdotal evidence to suspect so.
On 40 meters, against yagis at 130, 150', verticals have lost their
luster. 40m 4-Square remains solid alternative for those unable to put
up yagis at height.
I don't suppose you'd be willing to try a 160 dipole at *650* feet to
see if the lower lobe starts to intercept the angles you are playing
with the vertical?
----- Original Message -----
From: "Tom Rauch" <w8ji@akorn.net>
To: "TowerTalk" <towertalk@contesting.com>; <w7why@harborside.com>
Sent: Sunday, February 03, 2002 7:45 PM
Subject: Re: [TowerTalk] Modeling
> When my antennas blew down in our last storm, I just stuck the
> 10 meter antenna on top of the 20 meter to see what would
> happen. How about that, it worked. No modeling, no guess work,
> no scratching my head. Just stuck the antenna there and it
> worked. If I would have modeled it, probably would have told me
> it won't work. Think I'll just leave it there.
I installed a 318-foot tower because the model told me a simple
dipole up there would blow away my 3/8th wl vertical on 160.
Darn if the vertical doesn't win nearly all the time at any distance!
Am I glad I did it? You bet. Without actually doing it I never would
have known. Would I put the tower back up if it fell over? Not a
chance!
Would I think that dipole really played really really well without
direct A-B comparisons to what a vertical would do here at my
location? Almost certainly I would!
73, Tom W8JI
W8JI@contesting.com
______________________________________________________________________
__
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.net.
----------------------------------------------------------------------
-
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
________________________________________________________________________
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.net.
-----------------------------------------------------------------------
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|