On Sat, 22 Sep 2007 19:18:24 -0700, art wrote:

Richard , I have been reviewing antenna fundamentals as per the
engineering
handbook by Jasik second edition where it states

Equation (1-1)

efficiency = power radiated by antenna / power accepted by antenna

There is absolutely nothing stated here about "Gain" because radiation
is in every direction. An antenna is a passive device, it cannot
exhibit gain. Johnson and Jasik sez: "if one has a lossless antenna,
the directivity and gain are identical."

Equation (1-2): "The total power radiated from the antenna is" the
measurement of radiation intensity in watts/sr in every direction from
an antenna.

Equation (1-4): "Directivity is the measure of the ability of an
antenna to concentrate radiated power in a particular direction."
which is a sub-portion of the total radiation.

We can measure the total power of all radiation (EZNEC provides this);
we can measure the power accepted by an antenna (EZNEC provides this);
we can measure the power in a particular direction (EZNEC provides
this).

"The method of computing radiation patterns foir thin linear radiators
is basic regardless of length or complexity of shape "

There is for EVERY length.

"if one assumes
that the current from point to point is sinosoidal.

"for the case of a thin half-wave radiator which can be assumed to
have a sinusoidal current distribution"

This statement is NOT about efficiency and it specifically recites
what can be said about:
1. radiation patterns;
2. radiation resistance;
3. "gain" (directivity);
4. input Z.

We, in this group, quite typically express ALL of these qualities for
ANY antenna on the basis of SPECIFIC physical dimensions and
frequency. When we do, there is barely a half dB variation in any
answer, and often better when all SPECIFIC physical dimensions and
frequency are provided by the claim maker.

As you often fail to provide this SPECIFIC information, then your
claims descend into the category of myth and superstition (you can
call it hope and desire).

What I am declaring is the tank circuit
ala parallel circuit which demands a full wave length antenna is the
most efficient because the assumption by mathematicians is incorrect.

This is superstition.

This Voodoo can be easily tested. The first part of equation (1-1)
from the authors you quote demand you supply the SPECIFIC power
accepted by an antenna. You also fail to supply the second part of
equation (1-1) that states the SPECIFIC power radiated by the antenna.

Voodoo = 100%

So, to SPECIFIC counter proofs:

A half wave antenna in free space:
length = 33.43 feet
wire diameter = #12 wire
frequency = 14.28127 MHz
input Z = 72.12 ±j0.00 Ohms
Power accepted by antenna = 100W
Power radiated by antenna = 100W
Efficiency = 100%

Absolutely same antenna in free space at its full wavelength
frequency:
length = 33.43 feet
wire diameter = #12 wire
frequency = 28.463975 MHz
input Z = 4257 ±j0.00 Ohms
Power accepted by antenna = 100W
Power radiated by antenna = 100W
Efficiency = 100%

BOTH antennas exhibit radiation patterns IDENTICAL to Johnson and
Jasik. BOTH antennas exhibit input Zs IDENTICAL to Johnson and Jasik.
BOTH antennas exhibit radiation patterns IDENTICAL to Johnson and
Jasik. BOTH antennas exhibit radiation resistances IDENTICAL to
Johnson and Jasik. BOTH antennas exhibit radiation gain (directivity)
IDENTICAL to Johnson and Jasik.

When either of these two are off-center fed the efficiency DOES NOT
CHANGE:
Power accepted by antenna = 100W
Power radiated by antenna = 100W
Efficiency = 100%

nobody knows how a fractional wavelength antenna
really works

Total ignorance reveals:
Voodoo = 100%

Equation (1-1) and (1-2) are for any size antenna. All of this stuff
is in the FIRST TWO PAGES OF THE BOOK.

On the very first page of "Fundamentals of Antennas"
"If the current distribution on a wire is known ...
then the radiation pattern and the radiated power
can be computed."

Marconi could measure current distribution 100 years ago.

The authors, of course, give treatments for antennas of all sizes,
otherwise the book would only be three pages long.

Arthur, stop coloring the pages with your crayons long enough to try
reading at least these three pages. :-0

73's
Richard Clark, KB7QHC