"Yuri Blanarovich" wrote -

Efiiciency of the loaded radiator is roughly proportional to the area
under the
current curve along the radiator.
1. Placement of the loading coil can drastically affect that. (Base loaded
vs.
Top Hat loaded)
=========================

Typically, shifting the loading coil from the bottom of the antenna to its
most efficient location is about 1.5 dB at 7 MHz. Replacing a loading coil
at its most efficient location with a large top hat increases efficiency by
14 percent. Hardly drastic!

But Yuri's objective is not to find the optimum location of the coil along
the antenna. Every twopenny designer knows that THAT point exists.
Especially they who use rules of thumb. And there's nothing wrong with that.

The objective is to assist the coil designer to design coils by telling him
HOW to make use of the EXTRA knowledge of current distribution along the
antenna.

At present, it seems everybody assumes coil current has a uniform
distribution. Nothing wrong with that of course. Especially if everybody
makes the SAME assumption.

It is unwise to use "roughly" and "drastically" in the same context. After
all, it hasn't yet been discovered in which way the taper should go in order
to improve efficiency. (Yes, I know, you can't shift the taper.)

So that how is it proposed to alter the taper. Or to take advantage of it
by altering wire diameter, ie., by putting the lowest wire diameter in the
places where the smallest current flows. And vice-versa.

IF there is success in improving efficiency by, say, 1 percent, as a result
of increasing design and precision engineering costs, plus patenting costs,
plus testing and certification costs, plus manufacturing costs, by 5 or 10
times, would customers be prepared to buy it.

How accurate are (A-B) tests results expected to be? Within limits of
0.01%, 0.1%, 1% or 10% ?

You'll be lucky to obtain an accuracy of antenna power measurements within
+/- 20%, or within +/- 0.8 dB. This means you would be unable to GUARANTEE
to your customers an improvement in performance better (or worse?) than
about +/- 1 dB.

But an improvement of such a relatively large amount, by tinkering with
coils, I venture to say is impossible. So whatever improvement it is
expected to achieve it will be not be possible to honestly demonstrate it.
There is the possibility of an antenna actually being worse than measured.

But the $64,000 Question is whether customers will be prepared to pay for
another 0.5 dB or less gain, which may or may not exist. It would be like
searching for non-existent W.M.D.

On the other hand, it can be confident expected not to measure an antenna
gain worse than about 1 percent of what it actually is. But how do you
assess the difference between two antennas on the basis of back-to-front
ratio over an angle of 360 degrees in the presence of such small
differences.

It is suggested the next questions to ask are "What is the expected change
in improvement" and "How accurately can the expectation be measured".
Economics cannot be avoided.
----
Reg, G4FGQ