NEC-LIST: How Well Did the Wheeler Method Work?

Chip:

I (and I believe others) are interested in how well the Wheeler
(cap/can) method worked for your loops and dipoles. How closely did
your modeling match the Wheeler-method measured values for Rl, the
loss resistance?

Also, I agree that the antenna must be remote from ground in the
cap/can and that any ground-dependent antenna (i.e., vertical
monopole, etc.) is not a candidate for the cap/can method.

If one made a CFA at VHF or UHF, and if the ground isnt essential,
then the Wheeler method could be tried using a reasonable sized
cap/can.

I think that Jack Belrose's modeling of the voltage feed, and the
phases needed to make that work, may describe why some have had
trouble getting power out of the CFAs. The whole trick to getting it
to work has been the matching and phasing, since the Maxwell's
equations part has been fine from the start as far as I could
determine (but independent of the practical matter of getting it fed
properly).

All for now.

George

P.S. I used a full-scale chicken-wire-on-wood model of a jeep in
Thailand in 1967 to measure (with an ionospheric sounder--see my
article in the July 1973 IEEE Trans. AP article for details on the
method and my August 1970 IEEE Trans. VT article for data on the whip
on the jeep) the effect of using a vertical whip on the rear for NVIS
skywave at HF with the whip bent over the hood (as shown in the US
Army Field Manual, and which simulates an asymmetrical transmission
line) and with the whip bent out away from the vehicle (which
simulates an asymmetrical dipole). I dont recall the mesh size, but
it was a few inches and not a foot. It took me 20 years to get the
Army to modify their field manual (FM 24-18) to recommend the whip
tilted away (as used in Desert Storm with HMVEEs). But it only took
me a day, when I got a real jeep, to measure it and my chicken wire
model and get identical results (from an engineering standpoint). My
chicken wire was galvanized, but I didnt solder any joints. And it
didnt have time to rust. I earlier had good luck making a 10:1 scale
model of a PBY-6A flying boat to check out and idea I had of putting a
3-element Yagi with both Hpol and Vpol on a boom out the front of the
aircraft. This modeling showed that I could get away with just the
aluminum boom and the three horizontal elements as a "groundplane" for
the three vertical elements above the boom. In other words, I could
get away without having to have the vertical elements below the
boom. Since the frequency was 32.8 MHz, I would otherwise have to
mechanically raise and lower the lower vertical elements for takeoff
and landing. And I really dont like such mechanical systems to change
things on an aircraft while I am in it in the air! But my luck with
the wire model of the PBY-6A, and my subsequent check of the HPol and
VPol patterns in my first full-scale HF airborne pattern measurements,
with reasonably good agreement (in 1959), led me to use that approach
on the jeep and whip problem in 1967.
Received on Sat Apr 24 1999 - 20:32:00 EDT