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Old June 18th 04, 01:35 PM
iamnotglennsparks
 
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In , wrote:


Let's see..............An antennas bent so that the tip is parallel to
the ground?.............That represents an antenna that is now midway
between horizontal and vertical polarization.



Wrong. That represents an antenna with -both- horizontal and vertical
polarization.

Are you trying to misrepresent my statement? My statement is not
wrong. A antenna bent in the above fashion is now midway between
horizontal and vertical polarization. Such an antenna always has
fields in both polarizations. I never stated it didn't



First off, you are making a leap from 'having both polarities' to an
antenna being "midway between horizontal and vertical polarization",
whatever that means. From your explanation below I can only assume you
mean 'diagonal' polarization. But you can't get linear polarization
from a curved radiator, and the only straight sections of the antenna
were either horizontal or vertical. Maybe you can source your "midway"
polarization somewhere, huh?

Second, the whip has a larger diameter at the base than it does at the
tip, and is therefore more flexibile at the top than at the bottom.
Because of this the whip bent into a shape somewhat distorted from an
ideal 90 degree arc; i.e, the point on the arc at which the tangent of
the arc was 45 degrees to both vertical and horizontal was most
certainly -not- "midway" between the base and tip. So even if you
-could- source your "midway" polarization (and you can't) it would
probably not apply in this case.

Third, polarity is a 3-dimensional vectoral quantity. (Actually it's a
4-dim quantity if you include the scalar component. Regardless...)
This means that the "polar compatibility" (for lack of a better term)
between any two antennas is a factor not just of 'vertical' and
'horizontal', but also of wavelength/antenna length. This fact is
proven all the time with the use of some long-wire antennas which,
while clearly horizontal, are quite adept at receiving signals with
vertical polarity; and not only that but some are most efficient when
the wire is pointed directly at the source of the signal. IOW,
contrary to the popular (but mistaken) notion that antenna polarity is
as simple as 'vertical vs. horizontal', antennas exist which have a
polarity that is perpendicular to the signal in not just one, but
-two- dimensions, and they work quite well.

Also, polarity is a vectoral sum, which is not a -real- quantity but
an -effective- quantity. IOW, you can't bend a vertical antenna 90
degrees at the center and proclaim that the antenna has diagonal (45
degree) polarization. The fact is that you still have -seperate-
vertical and horizontal polarizations, but their -sum- is 45 degrees.
And that's true only in one dimension (don't forget that this is a
3-dimensional quantity). Any deviation from the one thin line that is
perpendicular to both polar components and the vectoral sum (the
-effective- polarity) will NOT be 45 degrees. This is not the case for
a straight radiator which, at any given point, will exhibit polarity
in TWO dimensions (a plane) that is fully perpendicular to the axis.

Even if you -did- bend the antenna 90 degrees at the center, that's no
evidence that the vertical and horizontal components will share the
same signal load. In a 1/4 wave vertical the top half of the whip is
primarily capacitive while the bottom half is inductive. Taken
seperately the bottom half is more efficient because it conducts the
most current. Bending the antenna in half would result in an antenna
with a strong vertical component and a weak horizontal component
(which is better than no horizontal component at all, and both results
are exactly what I observed in my test). And should there be an
-electrical- midpoint it would be much closer to the bottom of the
whip and not above the physical 'midpoint', the latter being the case
with the bend on my whip.

Finally, my antenna is a 1/4 wave, stainless-steel, vertical whip
(bent at the time) mounted on the front of an old Dodge truck. It is
certainly not an ideal example of laboratory precision, and I never
suggested it was. I did a test, I posted my observations, and I came
to my conclusion based on those results. I never suggested that my
test should be included in CRC's Handbook of Chemistry and Physics or
Van Nostrands encyclopedia. I never declared that a straight antenna
was better than a bent antenna or vice-versa. I never said that anyone
should or should not bend their antenna. In fact, I made no definitive
conclusion about my test other than what I stated -- the antenna had
both vertical and horizontal polarity. And you agreed.


The theoretical gain of that antenna should be equal between
polarizations. When such a scenario is in place the field strength
should drop to .707 of it's original. That represents a 3db loss
just from this antenna being bent.



Wrong. The theoretical gain of the antenna for a given polarity is a
function equal to the sum of the gains of equally spaced tangents
along the curve of the antenna.


Not wrong at all. A diagonal antennas field strength drops to .707 of
its original when the receiving antenna stays vertical.



That's only true if the receiving antenna is a half-wavelength.


Yet you stated....................................

"vertically polarized field strength dropped by a hair."



As measured by my FSM.


When testing mobile antennas a 3db loss is huge.
Most all well designed efficient non bent antennas
will easily beat your -3db antenna.



I did not say that it dropped by 3dB. The phrase "by a hair" is not my
words but the words of my spotter, and both of us generally use that
phrase to describe a meter shift approximately equal to the width of
the needle. And since the FSM used was only a 'relative' FSM (as
opposed to a CISPR quasi-peak detector), there is no way to quantify
"by a hair", nor did I attempt to do so.


Ok..........so your test is quantified by "hairs". Now I get it.



I doubt it.


My tests which were performed with much more detail were
chastised by you. Yet your test (the hair method) gets
validity.

I see how this works now.



No, you don't. But you will.....

The stated objective of your tests was to evaluate and quantify the
performance of various antennas, drawing conclusions that could be
extended beyond your testing conditions. However, the technical level
of the tests exceeded the limitations of your equipment, education and
experience. Your methods were less than scientific, your data was
superficial and contradictory, and your conclusions were few and
highly subjective. When the data from your first test didn't meet your
expectations you provided excuses. Your second test proved that your
excuses were wrong, so you made new excuses. Your data could not be
quantified, yet you proclaimed that x antenna was better than y
antenna was better than z antenna. You clearly failed to meet the
objective of your tests. You don't know why you failed, so you made
excuses for your failure. When you bragged about your tests in the
newsgroup I evaluated your failures one by one. You then blamed -me-
because you can't accept and correct your own failures.

OTOH, I did a simple test for fun, posted my observations, and
provided my very limited conclusion WITH WHICH YOU AGREED. So
according to -YOU- my test was both valid and conclusive.

Yet your obsession with me pushed you to try -- once again -- to
discredit me in a technical discussion. And once again you failed. And
once again you will blame me for your failure. If anything you should
be asking questions instead of trying to act like some sort of radio
guru (which you definitely are not).

NOW do you see how this works?







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