THE ONLY WAY TO ACCURATELY MODEL A LOADED VERTICAL


and similar coil and capacitance loaded structures, is as follows.


Let's take the most simple structure consisting of 3 sections - top, centre
and bottom.


The top is usually referred to as a whip or a rod.


The centre section is a loading coil.


The bottom section can be referred to as the mast.


All three sections have length and external diameter.


All three sections have uniformly-distributed inductance, capacitance and
resistance per unit length. All calculable from dimensions.


It is inescapable, therefore, the structure consists of -


THREE CASCADED TRANSMISSION LINES SECTIONS.


As with ALL transmissions lines, each section has a characteristic impedance
Zo, attenuation and phase-shift per unit length. All caculable from
dimensions.


The centre section, a solenoidal loading coil, clearly has inductance extra
to that due to the length of the coil former. The extra inductance is
calculable from the number of coil turns per unit length. If necessary
self-capacitance can be included.


ALL sections have a UNIFORMLY DISTRIBUTED radiation resistance which is
extra to conductor loss resistance. The two resistances are combined by
simple addition. Radiation resistance is itself obtained from the length of
a section.


CALCULATING PROCEDURE / PRINCIPLES.


This is done by using classical transmission formulae or by the well known
sufficiently accurate approximations.


Looking upwards from the base of the antenna -


(1) Calculate the input impedance at the bottom of the whip (or rod). The
whip is a transmission line open circuit at the top end.


(2) Calculate the input impedance at the bottom end of the loading coil,
the centre section. The centre section is a transmission line terminated by
the input impedance of the whip above it.


(3) Calculate the impedance looking up from the base of the antenna. The
feedpoint impedance. The bottom antenna section being a transmission line
terminated by the input impedance of the centre antenna section, the loading
coil.


(4) Connect a generator, the transmitter, between the base of the antenna
and ground. The ground will have its own 'input' resistance depending on the
ground electrodes or perhaps the vehicle characteristics.


(5) Using classical transmission line formulae, or their close
approximations, the amps, volts, relative phase-angles, can be calculated,
IF NECESSARY, at any point along the antenna, at any point along the coil,
from its base to the extreme tip of the whip


(6) But a full analysis is unnecessary. Nevertheless there's a big bunch of
calculations to be done to calculate radiating efficiency, a single number,
the ultimate solitary objective. Of what use to anybody is the difference
between input and output currents of the loading coil?


(7) The radiation pattern is eventually available. But even CB-ers are
familiar with the radiation pattern of a simple vertical antenna, loaded or
not, which is less than 5/8ths wavelengths in height.


(8) By an obvious extension of the above principles, a top hat on the top
of the whip, such as a set of radial wires within a ring, can be
automatically accounted for.


Now, you old-wives, what can be more simple than THAT? KISS!


I'm very sorry, due to recommendations by the medical profession, I have to
decline invitations to tea-parties in Boston, Mass.


And stop haggling amongst youselves. You have quite enough problems to sort
out on your side of the Atlantic.


As examples of practical use of the foregoing principles, download in a few
seconds and run immediately short, self-contained programs LOADCOIL and
TOPHAT2 from website below. Free to USA citizens.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

"Reg Edwards" wrote in message
...

THE ONLY WAY TO ACCURATELY MODEL A LOADED VERTICAL
snip
All three sections have uniformly-distributed inductance, capacitance and
resistance per unit length. All calculable from dimensions.
snip
THREE CASCADED TRANSMISSION LINES SECTIONS.
snip
Now, you old-wives, what can be more simple than THAT? KISS!
snip

simple or accurate??? you can't have both. in this case you have ignored,
among other things, that the capacitance between each infinitesimal part of
each vertical piece to the rest of the world is different. therefore your
transmission line sections are not uniform from end to end as needed to use
the classical transmission line formulations. Then of course you must also
consider that the actual radiated part of the field makes those
'transmission lines' appear extremely lossy... unfortunately that loss is
not the R and G type loss as the transmission line formulas use, though
those losses do also exist.

David Robbins wrote:

---------------
simple or accurate??? you can't have both. in this case you have ignored,
among other things, that the capacitance between each infinitesimal part of
each vertical piece to the rest of the world is different. therefore your
transmission line sections are not uniform from end to end as needed to use
the classical transmission line formulations.
---------------

But, since the 'classic' antenna calculations are only
approximate, how
much additional error would Reg's method entail, if any? I
think the
"simple -vs- accurate" thingy is one of the things that Reg was
getting at.
Very 'fiddly' (Hey Reg! I picked up an 'English' word, or would
that be
an 'UK-ism', sort of like an 'American-ism'?)...
'Doc

On Fri, 05 Dec 2003 12:06:42 -0600, 'Doc wrote:
But, since the 'classic' antenna calculations are only approximate,
how much additional error would Reg's method entail, if any?
Hi Doc,

Or more to the tenor of the purpose, how much accuracy would they add?
The point was in critical thinking and David's post extended that
horizon. This is all for the purpose of deriving a drive point Z,
which is the Three Card Monty of analysis.

73's
Richard Clark, KB7QHC

When you can write AND DEMONSTRATE QUANTITATIVELY programs which provide
even more accurate models/results than what I have provided then please make
them available to the world.

You have much to learn. From the zero level of bafflegab you have just
produced I'll give you another 40 years. As things are you are well on your
way to joining the 'old wives' brigade.

But please believe me. I have no wish to be unkind or discourage your
admirable young man's enterprise. By all means keep persisting.
---
Yours, Reg.

"Reg Edwards" wrote in message
...

When you can write AND DEMONSTRATE QUANTITATIVELY programs which provide
even more accurate models/results than what I have provided then please
make
them available to the world.

You have much to learn. From the zero level of bafflegab you have just
produced I'll give you another 40 years. As things are you are well on
your
way to joining the 'old wives' brigade.

But please believe me. I have no wish to be unkind or discourage your
admirable young man's enterprise. By all means keep persisting.
---
Yours, Reg.



it would help if you provided your model.

Reg,
I recommend the following pair of wonderful articles.
Part one is in HAM RADIO, April, 1977, pp. 52-58. The second in May,
1977, pp. 29-39.
The full reference is: Boyer, Joseph M. (W6UYH): "The
Antenna-Transmission
Line Analog".

Mr Boyer simplifies the antenna analysis by equating parts of the
antenna to transmission lines along the same lines that you have.
Regards
Nat

David,
I do like your reply to Reg since it evokes more thought
to the transmission line theory talk.
But the main point Reg, is I believe that all the group is in
in agreement with respect to current change and a 'large '
inductance, and those bonded to 50/60 hertz type thinking
have fled.
The only important thing left for some is to not
over react at the knowledge that lumped loads are theoretical
in nature since viewing same can provide advantages in
solutions for networks whether it be household frequency
or broadcast style frequencies.
Knowledge is what is valuable, whether that knoweledge
is inconsequential or not to ones needs.

As far as our problems in the U.S.A. Reg. As I pointed out
in a Letter to the Editor when presented with terrorism by
the Stern gang in London the U.K. handed the problem of
a homeland for Jews to the U.N. The U.N. never anticipated
that the U.S. by virtue of its veto, would support an expansion
of lands in the same way we did against the American Indian,
forgetting that if you can't kill them all then you have a
world wide conflict with respect to those who practice Islam.

Cheers and beers
Art


"David Robbins" wrote in message ...
"Reg Edwards" wrote in message
...

THE ONLY WAY TO ACCURATELY MODEL A LOADED VERTICAL
snip
All three sections have uniformly-distributed inductance, capacitance and
resistance per unit length. All calculable from dimensions.
snip
THREE CASCADED TRANSMISSION LINES SECTIONS.
snip
Now, you old-wives, what can be more simple than THAT? KISS!
snip

simple or accurate??? you can't have both. in this case you have ignored,
among other things, that the capacitance between each infinitesimal part of
each vertical piece to the rest of the world is different. therefore your
transmission line sections are not uniform from end to end as needed to use
the classical transmission line formulations. Then of course you must also
consider that the actual radiated part of the field makes those
'transmission lines' appear extremely lossy... unfortunately that loss is
not the R and G type loss as the transmission line formulas use, though
those losses do also exist.

it would help if you provided your model.

========================

There's a dozen of them to choose from at my website. Some been sitting
there for years. Moneyback guarantee. Present download rate averages around
200 per day.


When can we expect one of yours? Try an easy one first. What about doing a
10 feet length of 14 gauge plastic-insulated stuff? Don't forget end-effect
or you'll receive hate-mail from people suffering from delusions of
accuracy.
---
Reg

"Nat Gurumoorthy" wrote Reg,
I recommend the following pair of wonderful articles.
Part one is in HAM RADIO, April, 1977, pp. 52-58. The second in May,
1977, pp. 29-39.
The full reference is: Boyer, Joseph M. (W6UYH): "The
Antenna-Transmission
Line Analog".

Mr Boyer simplifies the antenna analysis by equating parts of the
antenna to transmission lines along the same lines that you have.
Regards
Nat

================================

Nat, Antennas and transmission lines are not just analogues - Antennas
ARE transmission lines with controlled 'leakage'. In fact, as people
forever complain on these walls, it is impossible to prevent a transmission
line FROM leaking.

Genuine guru's lump the names 'lines' and 'antennas' together in one volume.
They may mention in passing that the mathematics are identical to both in
case a casual reader doesn't realise it. But if Terman disdainfully omits
mention of the obvious there's always the danger that his disciples may
think it doesn't exist.

I produced the brief semi-serious description just for the purpose described
in the subject line ;o)
----
Reg, G4FGQ