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Old March 7th 08, 09:54 PM posted to rec.radio.amateur.antenna
Art Unwin Art Unwin is offline
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First recorded activity by RadioBanter: Mar 2008
Posts: 1,339
Default Antenna physical size

On Mar 7, 2:08 pm, (Richard Harrison) wrote:
Art wrote:

"No where can I find reference to "size" in what the masters state"

More diligence!

Terman never failed to have an answer for me. On page 864 of his 19550pus he writes:

"The simplest wire radiator or antenna is the elementary doublet shown
in Fig. 23-1a. This consists of a conductor of length small-delta l that
is short compared with the wavelength lambda, and which is assumed to
have such large capacitance areas associated with each end that current
flowing throughout the length of the doublet everywhere has the same
value I. The strength E of the field radiated from such an elementary
antenna in volts per unit length by a current I cos (omega t + 90
degrees) is given by the formula
E = 60 pi/d l/lambda Icos theta cos omega (t-d/c)
Eqn. (23-1)
Here d is the distance from the doublet to a distant receiving point P,
and theta is the direction of P with respect a plane perpendicular to
the axis of the doublet while c is the velocity of light. The strength
of the radiated field is distributed in space in accordance with the
doughnut pattern with a figure-of-eight cross section shown in Fig.
23-1b."

The above is only the beginning of Terman`s chapter on antennas. Fig.
23-2 shows how contributions from multiple doublets in a larger antenna
combine to produce the pattern of the larger antenna. Point to be noted
is that length over lambda is a multiplier in Eqn.(23-1). Obviously size
(length) does make a difference.

Best regards, Richard Harrison, KB5WZI


I disagree. Laws written are all based on the assumption of
equilibrium and that includes
Maxwell's laws. These laws hav e zero refernce to size as such though
many would seek
for the word volume. Pertinent factors are wave length of frequency in
use and root LC.
For equilibrium there is zero reference to size or volume. I ofcourse
fall back to the term equilibrium
which is a basic for Gauss's law of statics to which a variable time
can be added. Thus it can be seen that
a law can be stated that a radiator can be any size, shape or
configuration as long as it is in equilibrium.
The problem here is that amateur radio is wellded to the yagi design
which is not one of equilibrium
and the fact that amateurs and many of the higher educated have pushed
the term of equilibrium
outside the box. This shows up when the uneducated refer to small
antennas as being inefficient
based purely on the connection to a specific design without regard to
whether equilibrium exists
so that all the laws of the masters can be applied. Again, it is
implicite that all laws apply when
there is equilibrium, if there is not then the laws do not apply as
is.
With respect to the term
"length", this is not synonimous to "size" because it has only one
degree of freedom.
There is no reason why a radiator can be rolled up into any shape as
long as the laws of Maxwell
are adhered to and such a sample has been assigned for testing and I
have to be satisfied with the results
as they arrive.I will be soon using one on the radio for QSO's and I
apologise if its use offends anybody
Seems like the group is in quite a tizzy that a person would have a
small radiator that defies
that which has taken them years to memorize. I gave all pertinent
details how to make them
I also gave the mathematics and a sample where established computor
programs confirm the above
and now to upset all again I have given a sample for testing to a
independent reviewer.
There is no need for anybody to worry, Yagi designs still exist for
those who abore change,worry
about transmission line radiation or even radiators melting. When you
all understand the relevence of
equilibrium you can then procede to review the math, until then you
are all in left field.
Best regards
Art
There is nothing in Maxwells laws that prohibit a "wavelength" from
being condensed into the
size of a pinhead or smaller and still be "efficient" with respect to
stated paramitors.