Re: NEC-LIST: Coil-loading -- 2

I skipped ahead a bit too quickly. The method I used in 1953 was
based on linear current distributions on the antenna. Later I
modified my techniques ("VLF, LF, and MF Antennas", Chapoter 15, The
(IEE) Handbood of Antenna Design, Volume 2, Peter Peregrinus, London,
UK, 1983) to assume cosinusoidal current distribution on the antenna
--- and so my technique can be used for antenna heights as large as a
quarter wave, or more. I show in the book impedance calculations for
antenna heights from very electrically small to 5/8 wavelength.

73, Jack, VE2CV

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Doug,

My first article on the subject was published in QST September 1953
issue, "Short Antennas for Mobile Operation", based on theory and
measurement. The most difficult measurement was to measure the
Q-factor of the inductor used to tune the antenna --- the self
resonant frequency of the coil has to be high, high compared with the
operating frequency. I finally fabricated an inductor that was
reasonably satisfactory --- but it was still a close wound coil!!

The analytical analysis method I used is based on the methodology
described in Edmund Laport's classic book Radio Antenna Engineering,
McGraw Hill 1952 (Laport is now a silent key) --- considering the
antenna as an opened-out-transmission, but the equations given were
developed by me.

I did not devise the technique, but (in my view) I was first to
analytically analyze center-loaded whips --- developing equations to
calculate the inductor required to tune, and radiation resistance.
If you take a look at that paper I show a graph showing the optimum
location of the coil.

Many years later Bob Hansen (in 1975), see [1, 2], was, in my view,
the first to use numerical moment methods to model center-loaded
whips. Bob (a long time colleague) considered my methods sort of
"back-of-the-envelope techniques", but in his later paper that year
he had to admit that my method was on the right track --- in fact
not only the 'right-track" but numerically correct. But neither Bob
(and certainly not me) modelled the antenna in its operating
environment (on a vehicle). The antenna is fed against the metal
structure of the vehicle, and so the vehicle is a part of the antenna
system.

My latest article on the subject was written in 1993 [3] --- based
on rigorous numerical modelling techniques, NEC-4D, and (more)
rigorous field strength measurement.

73, Jack, VE2CV

1. Hansen, R.C., "Efficiency and matching trade-offs for inductively
loaded short monopole antennas", IEEE Trans. on Comm., COM-23, April
1975, pp. 430-435
2. Hansen, R.C., Optimum inductive loading of short whip antennas,
IEEE Trans. Veh. Tech., VT-24, 1975, p. 21
3. Belrose, J.S. and L.Parker, "A tunable all-bands HF Camp/Mobile
Antenna", Communications Quarterly, Fall 1998, pp. 47-57.

>Good day,
>
>I recently read John Belrose's "Short Coil-Loaded HF Mobile
>Antennas..." in ARRL's "Vertical Antenna Classics". He
>claims the first analysis article in a 1953 issue of QST,
>which leads me to wonder who discovered or invented the idea
>and when?
>
>Thanks,
>Doug Miron
>
>--
>The NEC-List mailing list
>NEC-List_at_robomod.net
>http://www.robomod.net/mailman/listinfo/nec-list

-- 
_____________________________________________
John S. (Jack) Belrose, PhD Cantab, VE2CV
LIFE SENIOR MEMBER of the IEEE
TA ARRL
Fellow Radio Club of America
Life Member AWA
Life Member QCWA
Athlone Fellow
Radioscientist Emeritus Researcher
Communications Research Centre Canada
PO Box 11490 Stn. H
OTTAWA   ON   K2H 8S2
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