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Old November 15th 09, 08:45 PM posted to rec.radio.amateur.antenna
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Default Causes of Distrust of NEC and Mininec programs

On Nov 15, 12:29*pm, Richard Fry wrote:
Art Unwin wrote:
What one gains from this aproach is that any radiator
of any shape, size or elevation can provide figures in
the order of 100% as long as the radiator is a multiple
of a wavelength where it is resonant at exact and
repeatable measurements.

then Art wrote:
The use of the term "nearly" does not imply total accuracy.


Note that your use of the phrase "in the order of" does not
imply total accuracy, either -- even for radiators meeting
your criteria.

To use Maxwell's equations for accuracy one cannot introduce
metrics that are not absolute. 1/4 or 1/2 wave radiators cannot
supplant the "period" of a wave form and thus introduce
inaccuracies.


Apparently you believe that only full-wave radiators are
"perfect" (exactly 100% efficient).

Until antenna programs all of which are based om Maxwell's equations
provide accountability of all forces involved to provide the 100%
efficiency, as shown by the use of
full wave radiators I have no other choice. It is as the catholic
religeon teachings when it says "give me the child and I will give you
the man." Its equivalent in education is to believe
only what the professor tells you that is written in his books as it
is he who determines
who graduates or not. Many of the masters did not have a formal
education such as Greene who had to justify from first principles
himself to determine what was correct and what was not. After serving
most of your years in life by adhering to the books it make no sense
in changing from a follower to a reseacher when the past has satisfied
your need.
As with religeon faith will always overide the tenents of science,
more so as you get older.

However a full-wave, center-fed dipole has a radiation resistance of
about 2,000 ohms, and a feedpoint reactance exceeding 1,000 ohms
(capacitive). *That impedance would present a very high VSWR to a
normal transmitter unless some kind of matching network was used.

Even if there was no matching or transmission line loss (or r-f ground
loss in the case of a monopole), that full-wave radiator still would
not be 100% efficient because of the ohmic losses encountered by the r-
f current flowing along the radiating structure (NOT the radiation
resistance).

RF




 
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