[TowerTalk] Vertical Antenna Points

[Jim Reid]

Aloha LB,

Boy,  very sorry to hear of your discomfort these past several days;
sure helps open our eyes to how we take so many things for
granted when they are withdrawn!! We had a similar experience
going on for weeks after hurricane Iniki out here in 1992;  trust
another of those will not be along for some good long time,  hi.

Thank you much for your many thoughtful comments.  I am forced
to a compromise situation for sure.  My primary concern is
the power transfer efficiency.  I assume the radiating  pattern
would probably favor the directing of the radials,  rather as it
does for inverted L's,  etc.

With regard to your first point:

"1.  The modeling study on vertical dipoles and their use or non-use of GPs
was intended as a report to show what modeling via NEC (or MININEC) would
suggest about the use of GPs with that type of antenna.  Remember that the
antenna is a "complete" antenna, which for my purposes, means that it will
model in free space correctly, relative to applications closer to a ground
system."

Suppose  I did the following,  to make this thing look as a "complete
antenna" would,  i.e.,  vertical dipole.

This is the direction,  to the extent that I can,  I am going.  I plan on
increasing
the height of my high band Gladiator triple bander ( again for those not
familiar with these,  see
    http://www.primenet.com/~bmyers/triple.htm

The bar across the 20 meter vertical element to which the
15 and 10 meter elements are attached is now about
24 feet in the air as viewed by the soil outside the house,
but of course only around 14 feet or so above the roof shingles.

Now,  if I were to use a 36 foot Radio Shack push up pole,
and not totally extending it,  I could raise that bar on up
to possibly 30 feet above the roof,  or 40-45  feet in the air.

Now,  were I to have only one single wire hanging down from
that common bar,  one for each band (not two symmetrical
wires),  would this not now configure a vertical (or nearly
so) set of three parallel dipoles?  That is,  per your
point #1, as quoted above,  would be three parallel vertical
dipoles up there,  and quite independent of ground
plane behavior?

Of course there is this  30 foot long metal pole paralleling
the downward going wires completing the vertical dipoles
which is going to introduce some parasitic coupling of some
sort,  I am sure,  hi.  But it will not be resonant with any of
the bands,  I hope!!

Seems to me,  in this situation,  we are completely away
from the problem of the incomplete vertical monopole;
unless,  my height  at H.F. is still too close to the ground,
unlike your VHF ground plane antenna example up at
30 feet.

Horizontal dipoles on these bands up at 40+ feet above the
soil work pretty well,  I believe.  I must go back and re-read
Rick Karlquist N6RK's,  experimental work with vertical
dipoles.  He concluded they worked no better than a hor-
izontal dipole at the same feed point height,  I think.
Such performance,  under my now space restricted
circumstances would be quite acceptable to me.

Anyway,  thank you again for your comments,  LB.
If I am looking at this still incorrectly,  would appreciate
another steer from the Professor,  hi.

73,  Jim,  KH7M



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