Re: Causes of Distrust of NEC and Mininec programs

On Sat, 14 Nov 2009 22:23:05 -0800 (PST), Art Unwin
<arthurunwin@xxxxxxxxx> wrote:

Cebic found when comparing different style programs that some behaved
well in certain circumstance where others did not.

True. When circumstances dictate that I pay attention and I'm in a
good mood, most programs behave normally. However, when circumstances
are not so favorable, such as last week when I replaced my septic
tank, all of the software I was using literally stunk.

Fact is that most users use fractional wavelength designs, usually
a half wavelength, that is not resonant at repeatable points where
the area around the datum line of a sine wave is never equal when
generated around a tank circuit.

Last time I checked, the definition of a half wave automagically
includes any external or magical factors that might change its length.
For example, if you submerge the antenna under water, the increased
dielectric constant will cause the half wave length to somewhat
shorten. While the previous length has changed, the new shorter
length is still a half wavelength.

The reason for this is "voltage over shoot" which gets smaller
with every cycle but never disappears.

Overshoot can easily be fixed with a Cutts Compensator.
<http://en.wikipedia.org/wiki/Cutts_compensator>
Every time you cycle your antenna, the recoil tends to make the barrel
climb a bit. This is the cause of the overshoot. A suitable Cutts
Compensator attached opposite the feed point should help prevent
overshooting the target.

Thus when programs are used
based on fractional wavelength radiators the results will never show
100% accountability and in fact efficiencies derived will be in the
order of 92%!

95.718% of all statistics are wrong. If you're using single digit
accuracy and single digit significant figures, 92% rounded off is
equal to 100%.

If the radiator is of a wavelength then one is not using a "fudge"
figure
in the calculations and then becomes possible to attain total
accountability with efficiency of 100%. regardles of what type program
is used.

Half wave wire dipoles do tend to be resonant somewhat shorter than
the free space wavelength. That's due to sales and value added tax
placed on antennas by the government. You'll always come out a bit
short when dealing with them. However, the last time I checked, the
cut length was only about 5% shorter than the free space half-wave
length. Did the antenna tax increase to 8%?

If one is to use exact equations, as are Maxwell equations, then
one must also use measurements that are also exact and repeatable and
that is definitely not fractional wavelengths!

My antennas are exact and repeatable. Not only that, I can also
repeat my mistakes every time.

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.

Perhaps. If you buy your antennas out of state or on eBay, you can
avoid paying the 5% antenna length tax. However, you are required to
pay Use Tax on any out of state purchases where the vendor neglected
to collect the antenna tax and forward it to the Calif Franchise Tax
Bored:
<http://www.ftb.ca.gov/current/usetax.shtml>

If anybody can give pointers that refute the accuracy of the above I
would be very interested in hearing them

Why? You haven't proven your point, demonstrated the phenomenon, or
otherwise provided anything worth tearing apart. For all I know, your
antennas are shorter than expected because of magic, enchantment,
sloppy construction, mis-measurement, or all the aforementioned.
Anyway, the problem is easily solved. Just increase your AC power
line voltage about 5% and your numbers should increase by the same
amount.

--
Jeff Liebermann jeffl@xxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.

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