I don't think it's unreasonable to discuss their performance, and
consider the findings Yuri has presented as being both reasonable and
viable.

73, Jim AC6XG


I am just amazed that with all the "theoretical" arguing going on, why none of
the "learned" experts measure, answer or explain the following REAL effects or
show where I (we) are wrong:

We are assuming quarter wave electrical (90 deg) antenna with loading coil
inserted from 50 - 70% of the radiator length.

1. As I mentioned and got only fuzzy arguments (poor coils, metal caps, poor
connection, which do not jive with observations), having let's say 80m mobile
Hustler antenna (many of them around) with coil. Put 100W to it (no
obstructions, meters, things to detune it) for about 30 secs. Go feel the coil,
or if you have thermal strips, watch the color from bottom to top. You will
notice warmer bottom. Put 500W to it, you will "reshrink" the tubing,
heatshrink tubing will start curling from the bottom, insulation on wire will
start blistering. I have done it, I saw it, I melted the bottom of the coil.
K0PP is sending picture of similarly fried Minooka Special. Why coils melt at
the bottom and not all along if the current is uniform across the coil?
Explanation: Uniform coil, with uniform wire, on uniform form, same caps on top
and bottom, the resistance is the same along the coil. If R is the same, and
there is more heat developed in part of the coil, then according to I2R
formula, current MUST be HIGHER in the part of the coil that heats more - at
the bottom. If the current is higher at the bottom part of the coil, it cannot
be the SAME at both ends.
Do not believe me? Everybody can do the test with mobile coil and verify it.
You don't need meters and nothing disturbs the setup. This demonstartes that
current is not uniform accross the coil, it larger at the bottom than on top.
Where are we wrong here?

2. As I quoted on my page http://www.k3bu.us/loadingcoils.htm results of W9UCW
test and measurements, Barry measured in the controlled environment, (60
radials, good coil, RF ammeters) that current in loading coil varies between
top and bottom in the range of 40 - 60%,. which confirms the effect described
above and puts some figures on it. It was done on different bands, with
different positions of the coil and generally follows the pattern. RF ammeters
are designed for this particular type of measurements. We get the same
conclusion and confirm the effect - the current in the loading coil varies
across the coil, it is not the same.
What is wrong with those measurements and results? Again anyone can verify
them. Did anyone measured anything different?

3. Lets look at the RF choke. Coil the piece of coax into a coil with enough
inductance to suppress RF current. Is the current same at both ends?

4. W9UCW used toroid loading coil and got the same results. How could that be?
It was MEASURED not "figured" out.

5. Cecil explained the reflected wave situation and delay in the coil, which
supports and explains the mechanism of the phenomena.

6. ON4UN in his Low Band DXing book for years has shown and explained the
distribution of current in various configurations of loading coils, hats, stubs
and clearly shows that current across the coil decreases in proportion to the
electrical degrees of the radiator that it replaces. Where is he wrong? Another
engineer that "knows nothing"?

7. How could it be if the voltage (neon bulb test) is increasing along the coil
towards the top, current has to be decreasing.

Can we see some other (better) measurements, anyone?
Or is all the above fantasy, because EZNEC says so?
Can we have some REASONS instead of ridicule? Point by point please.

Yuri, K3BU.us

Roy Lewallen wrote:

I'm not sure why anyone would think that you can treat an antenna, or a
loading coil of significant length, as a lumped element and expect to
get anything resembling accurate results.

Roy, have you read the arguments that started this discussion?

They are at: http://www.k3bu.us/loadingcoils.htm

Please tell us if you agree with John Devoldere's "Bible" -
"ON4UN's Low Band DXing", 3rd Edition, on page 9-34:
--
73, Cecil http://www.qsl.net/w5dxp



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Ian White, G3SEK wrote:
This brings us back to the question of practical loading coils, and how
much radiation (and therefore current variation along the length) we can
expect.

For the feedpoint impedance to be purely resistive in an electrical 1/4WL
shortened vertical, the current must undergo a round trip phase shift of
360 degrees and the voltage must undergo a round trip phase shift of 180
degrees. The loading coil must provide the phase shift that the antenna
doesn't provide. For a typical 75m 8 ft mobile antenna, the coil must
provide approximately 80 degrees of phase shift.
--
73, Cecil http://www.qsl.net/w5dxp



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Art Unwin KB9MZ wrote:

If reactance can be seen as a "{missing" part
of a radiator how should we view what a
capacitor represents? Grin

A series cap has the opposite effect of a series coil. I have seen
such antennas made out of end to end caps but I've never really
understood their claim to fame.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote in message ...
No, I will make one more comment. After a bit of reflection, I think
this might be at the core of some people's problem in envisioning a
lumped inductor.

When a current flows into an inductor, it doesn't go round and round and
round the turns, taking its time to get to the other end. An inductor
wound with 100 feet of wire behaves nothing like a 100 foot wire. Why?
It's because when the current begins flowing, it creates a magnetic
field. This field couples to, or links with, the other turns.

This is the way I view it, and why I couldn't automatically endorse
the fairly large difference they saw. Unless the coil is very long,
say as in a helical whip, I see it acting pretty much as a lumped
inductor. Sure, the current may vary some through the coil when it's a
foot or so long bugcatcher coil, but I don't see it being a major
issue. I wouldn't normally expect to see a sharp current taper across
the coil. I see that type of coil acting much as a "one piece" lumped
inductor, not as a many turned rf roller coaster ride. Not a perfect
lumped inductor, but close enuff for average gov work. MK

Cecil Moore wrote in message

A bugcatcher coil on a 75m mobile antenna also does not meet the
definition of a lumped circuit.

Dunno. I think it does. Not perfect by any means, but I still think it
"acts" pretty much like a lumped inductor. MK

Cecil Moore wrote:
Ian White, G3SEK wrote:
This brings us back to the question of practical loading coils, and
how much radiation (and therefore current variation along the length)
we can expect.

For the feedpoint impedance to be purely resistive in an electrical 1/4WL
shortened vertical, the current must undergo a round trip phase shift of
360 degrees and the voltage must undergo a round trip phase shift of 180
degrees. The loading coil must provide the phase shift that the antenna
doesn't provide. For a typical 75m 8 ft mobile antenna, the coil must
provide approximately 80 degrees of phase shift.

I'm sure you'll find the answer in Balanis, if you read it with an open
mind instead of trying to force him to agree with you.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Mark Keith wrote:
This is the way I view it, and why I couldn't automatically endorse
the fairly large difference they saw. Unless the coil is very long,
say as in a helical whip, I see it acting pretty much as a lumped
inductor. Sure, the current may vary some through the coil when it's a
foot or so long bugcatcher coil, but I don't see it being a major
issue. I wouldn't normally expect to see a sharp current taper across
the coil. I see that type of coil acting much as a "one piece" lumped
inductor, not as a many turned rf roller coaster ride. Not a perfect
lumped inductor, but close enuff for average gov work. MK

The round trip current phase shift in an electrical 1/4WL vertical must
total 360 degrees. If the coil doesn't perform part of that phase shift,
what does?
--
73, Cecil http://www.qsl.net/w5dxp



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Mark Keith wrote:

Cecil Moore wrote in message
A bugcatcher coil on a 75m mobile antenna also does not meet the
definition of a lumped circuit.

Dunno. I think it does. Not perfect by any means, but I still think it
"acts" pretty much like a lumped inductor. MK

Where does the rest of the necessary phase shift in the round trip
current come from if not from the coil?
--
73, Cecil http://www.qsl.net/w5dxp



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Ian White, G3SEK wrote:

Cecil Moore wrote:
For the feedpoint impedance to be purely resistive in an electrical 1/4WL
shortened vertical, the current must undergo a round trip phase shift of
360 degrees and the voltage must undergo a round trip phase shift of 180
degrees. The loading coil must provide the phase shift that the antenna
doesn't provide. For a typical 75m 8 ft mobile antenna, the coil must
provide approximately 80 degrees of phase shift.

I'm sure you'll find the answer in Balanis, if you read it with an open
mind instead of trying to force him to agree with you.

Ian, I learned the above in the class I took from Balanis at ASU in 1995
while I worked for Intel in Chandler, AZ. I asked him a lot of
questions about center-loaded antennas as they are not covered well
in his book. The fact that none of the resident gurus on this newsgroup
will touch the above simple question with a ten foot pole speaks volumes.
A very bright engineer has been in email contact with me over this deductive
reasoning problem. So far, he has not attempted to resolve the conflict
between a lumped inductor and the absolutely necessary phase shift.

Here is the answer to the question presented by Devoldere in "ON4UN's
Low Band DXing". For convenience sake, I will draw the vertical mobile
antenna as one half of a dipole but the same logic applies. Note the
coil is drawn in electrical degrees, not in proportional physical length.

wire coil wire
-----------////////////////////////----------
22.5 deg 45 deg 22.5 deg

We know from the end result that this is what has to happen. An electrical
1/4WL antenna simply must cause a 90 degree phase shift in the current
from end to end. Otherwise, it wouldn't be an electrical 1/4WL antenna.

Until someone can explain exactly how a lumped inductor causes a 45 degree
phase shift in the current, I am going to assume that a lumped inductor
is incapable of that feat.
--
73, Cecil http://www.qsl.net/w5dxp



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