On 29 Oct 2003 18:58:40 GMT, oSaddam (Yuri Blanarovich)
wrote:

It looks like this factor is not properly accommodated in modeling programs
using loading inductors in antenna elements. In view of the above, time
permitting, I will try to do some work and try to shed some more light on the
subject.

Hi Yuri,

With respect to the data:
Here are some actual measurements of current below and above loading coils.
92" mast, using a HI-Q coil (openwound airdux, 2 1/2"d) with small thermocouple
type meters mounted on the insulated coil support. First for 40m, moving the coil
in the mast from base to center to top (with hat) and reresonating.
Base --100ma below & 66ma above
Center --100ma below & 45ma above
Top --100ma below & 37ma above

This speaks more of simple Resistive heat loss supported by your own
direct observation of:
I fried the loading coil with 600W into Hustler resonator,
melting heat-shrink tubing and wire at the bottom of the coil.

As you, through personal testimony, offer that the bottom of the coil
was warmer (hotter even) than the top; and further, given that the
measuring device is caloric based (thermocouple) it stands to reason
that the close association to heat inflates the base reading not
through the evidence of higher current, but higher (and demonstrable)
heat. The pictures show the close proximity of the thermocouples to
the heat source/coil and also reveal no readings at greater distances
from the coil.

You go to great lengths to portray the current distribution along the
entire length of the radiator from authoritative sources, and yet you
do nothing to confirm them; except over the small portion that
fascinates you and is prone to just such systematic error as I
describe.

73's
Richard Clark, KB7QHC

Richard KB7QHC wrote:

This speaks more of simple Resistive heat loss supported by your own
direct observation of:
I fried the loading coil with 600W into Hustler resonator,
melting heat-shrink tubing and wire at the bottom of the coil.

No, it confirms that there is a significant (not negligible) difference in the
current at the bottom vs. top of the coil. Yes, Hustler has small (almost
resistive) wire on 80m resonator. If you trasmit for short period of time (not
enough for heat to equalize) and feel it, or use thermal strips to check
temperature, you would see the taper in the current from bottom to top. It is
in order of 50%, not negligible. Coils in tests are good quality, not
"resistive" wire, current relatively low (100mA) as shown in W9UCW measurements
and pictures.

The point is, if the current was constant or close to it, you would not see the
difference as we see it. Heat rises to the top, if anything the top would be
warmer if the current was constant. If the coil is uniform colenoid, same wire,
diameter (resistance), spacing and it shows difference in heat produced accross
the coil, then we can, using I2R formula, deduct that that current at the
bottom is greater than on the top. W9UCW measurements confirm that, Cecil
explains. Speculations that Earth must be flat might satisfy those reading the
(wrong) books, but will not jive with reality.

Simple way to test it, transmit 100W to 80m Hustler resonator, and feel the
coil. Even insensitive people can feel the significant difference in
temperatures. Put 500W to it for longer period and watch the heatshrink tubing
shrivel from the bottom up. This eliminates all the "errors" with meters to
prove the point.

Yuri, K3BU/m

On 30 Oct 2003 13:59:54 GMT, oSaddam (Yuri Blanarovich)
wrote:

Richard KB7QHC wrote:

This speaks more of simple Resistive heat loss supported by your own
direct observation of:
I fried the loading coil with 600W into Hustler resonator,
melting heat-shrink tubing and wire at the bottom of the coil.

The point is, if the current was constant or close to it, you would not see the
difference as we see it. Heat rises to the top, if anything the top would be
warmer if the current was constant.

Hi Yuri,

Your testimony contradicts your sentiments. You offer
incontrovertible evidence of heat at the bottom of the coil explicitly
in your statement above, and this below:

Simple way to test it, transmit 100W to 80m Hustler resonator, and feel the
coil. Even insensitive people can feel the significant difference in
temperatures. Put 500W to it for longer period and watch the heatshrink tubing
shrivel from the bottom up. This eliminates all the "errors" with meters to
prove the point.

You are using a thermocouple which is sensitive to heat, the heat of
coil loss will inflate the reading. You have twice offered heat at
the bottom of the coils that correlate strongly with inflated current
values from a caloric sensor. You have no other thermocouple data
supporting the nature of the current distribution, just the isolated
section you find attractive. Put simply, your measurements have no
reference (readings from the entire length of the radiator).

You went to some trouble to offer testimonial from reference sources
on the nature of that distribution, but you did not measure it confirm
your testing. Two readings in isolation do not prove you have 100mA
into the bottom when there is only one reading below the coil.

If you are not interested in obtaining those remaining readings of
that current distribution, then you have a poor case.

73's
Richard Clark, KB7QHC

You are using a thermocouple which is sensitive to heat, the heat of
coil loss will inflate the reading. You have twice offered heat at
the bottom of the coils that correlate strongly with inflated current
values from a caloric sensor. You have no other thermocouple data
supporting the nature of the current distribution, just the isolated
section you find attractive. Put simply, your measurements have no
reference (readings from the entire length of the radiator).


The bottom meter is below the coil, so there is no heat heating up the
thermocoupled meter. If you insert the meters some distance away from the coil,
you would see the corresponding readings showing the difference between the top
and bottom. Arguments that heat or magnetic field affect the thermocouple RF
ammeters are just not realistic.

You went to some trouble to offer testimonial from reference sources
on the nature of that distribution, but you did not measure it confirm
your testing. Two readings in isolation do not prove you have 100mA
into the bottom when there is only one reading below the coil.


I did just rough test with one of my meters (has 8 A), flipping the coil and I
can see some deflection at the bottom and none at the top with 100 W into the
antenna. W9UCW et al did hundreds of measurements and showed just some
examples.

If you are not interested in obtaining those remaining readings of
that current distribution, then you have a poor case.


My "case" is to bring this to attention of those who are still "knowing" that
the current in loading coils is the same at both ends. If they doubt, they can
do their own measurements and see what it is, or show us where we are wrong.
Again, ON4UN in his Low Band DXing book has it right, ARRL Antenna Book has it
wrong and is perpetuating 50 year old misconception.

Just MEASURE or FEEL it!

73's
Richard Clark, KB7QHC

Yuri, K3BU/m

On 30 Oct 2003 23:19:00 GMT, oSaddam (Yuri Blanarovich)
wrote:


You are using a thermocouple which is sensitive to heat, the heat of
coil loss will inflate the reading. You have twice offered heat at
the bottom of the coils that correlate strongly with inflated current
values from a caloric sensor. You have no other thermocouple data
supporting the nature of the current distribution, just the isolated
section you find attractive. Put simply, your measurements have no
reference (readings from the entire length of the radiator).


The bottom meter is below the coil, so there is no heat heating up the
thermocoupled meter
....
Just MEASURE or FEEL it!


Hi Yuri,

As I said, your testimony contradicts your sentiments (for the third
time now). As you offer no inclination to provide more data (a
complete survey along the entire length of the radiator using the
thermocouple devices), this is not much in the way of proof.

73's
Richard Clark, KB7QHC

Yuri Blanarovich wrote:
My "case" is to bring this to attention of those who are still "knowing" that
the current in loading coils is the same at both ends.

The current can be the same at both ends if the coil is positioned at a
current minimum or current maximum point which is NOT the case with
mobile antennas.

The key to understanding is to recognize that the coil causes the
opposite phase change in the forward current as it does in the reflected
current so they *cannot* track each other through the coil.
--
73, Cecil http://www.qsl.net/w5dxp



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oSaddam (Yuri Blanarovich) wrote in message ...


Any experiences out there, rather than more "reasons" why it ain't so?
Proper accommodation in modeling programs can give substantial improvement in
loaded elements modeling.

Let the games begin :-)

Yuri, K3BU

Dunno, I think it varies. But I sort of agree with Tom, I think it's
fairly constant across the coil. The reason I think so, is because the
electric field across the coil is also constant, and I can easily see
that using a fluorescent bulb across the antenna and coil. Sure, there
may be some decrease, but that could be due to wire resistance loss.
Also, the construction of the antenna itself could vary the current
across the coil. If the whip is top loaded, and the current would be
linear up the whip anyway, I would think it would also be linear
across the coil, no matter where it was. If the coil were base loaded,
with the sharply tapering current distribution up the whip, the taper
across the coil *might* be more. Another reason I think it's fairly
constant is because if I elevate the coil up the whip, I also elevate
and improve the current distribution. The current will be fairly
constant all the way up to the top of the coil, and then start to
taper off as you go up the "stinger" part of the whip. If the
distribution were not fairly linear across the coil, I don't think you
would see this. I'm sure it's not perfectly linear, but I think it is
for all *practical* purposes. And like I said, probably can vary from
antenna to antenna. I haven't read the eham thing yet, but I guess
this is my wishy washy vote... MK

NM5K

Dunno, I think it varies. But I sort of agree with Tom, I think it's
fairly constant across the coil.

MEASURE or FEEL it! Or disprove what W5DXP is saying.

It appears that current drop is proportional to the current drop in the section
of the antenna that is "missing" - replaced by the coil. You can express it in
electrical degrees and it appears to correspond to cosine distribution.

Yuri, K3BU

Yuri Blanarovich wrote:
MEASURE or FEEL it! Or disprove what W5DXP is saying.

This is easy to see using EZNEC. Model a 102' G5RV on 20m
and look at the current distribution. There are three
current maximums and four current minimums. If you install
a loading coil at a current maximum or current minimum, the
current magnitude will be the same on both sides of the coil.

If you install a loading coil at a point where the slope of
the current is negative (decreasing), the current at the bottom
of the coil will be greater than the current at the top of the
coil. This is the usual case for mobile antennas.

If you install a loading coil at a point where the slope of
the current is positive (increasing), the current at the bottom
of the coil will be less than the current at the top of the
coil.

Note: 'Top' of coil is the end closest to the the ends of the
antenna. 'Bottom' of coil is the end closest to the feedpoint.
--
73, Cecil http://www.qsl.net/w5dxp



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oSaddam (Yuri Blanarovich) wrote in message ...
NM5K

Dunno, I think it varies. But I sort of agree with Tom, I think it's
fairly constant across the coil.

MEASURE or FEEL it! Or disprove what W5DXP is saying.

Dunno, he seems to be saying about the same thing. It depends where
the coil is mounted.

It appears that current drop is proportional to the current drop in the section
of the antenna that is "missing" - replaced by the coil. You can express it in
electrical degrees and it appears to correspond to cosine distribution.

I could buy that to an extent I guess. But say if you had a top loaded
vertical, with linear current distribution, the current across the
coil should be appx equal no matter where the coil is placed. But if
no top loading, maybe so.. MK