wrote in message
ups.com...
This thread belongs back in the original place, so it flows in context.

Sorry I had to take a break and lost the place in original place, so lets
try to continue here, we are trying to go step by step.

Yuri Blanarovich wrote:
OK, I have been accused of being wrong, claiming that current across the
antenna loading coil is or can be different at its ends.

No one said that.

So what is it then you claiming being equal.

I and "my camp" say that we are seeing somewhere 40 to 60 % less current
at
the top of the coil, than at the bottom, in other words, significant or
noticeable drop.

Quit trying to make it a gang war. It is antenna theory, not a bar
room brawl with a bunch of drunks.

No gang wars intended, just trying to underline that there are two major
supporting "camps" claiming that the current has to be equal, or is
appreciably different.

W8JI and "his camp" are claiming it can't be so, current through the coil
has to be the same or almost the same, with no significant drop across
the
loading coil.

I have no camp. You are lifting what I say out of context and deleting
important things.

What I say, over and over again, is I can build an inductor in a short
mobile antenna that has essentially equal currents at each end. A
compact loading coil of good design has this type of performance.

I can do that too and do not deny it.

The current taper across the inductor is not tied to the number of
"electrical degrees" the inductor "replaces". It is tied to the
distributed capaciatnce of the coil to the outside world in comparison
to the termination impedance at the upper end of the coil.

That too, but that seems to be minor cause. Lets do it step by step.
I will skip agreements so far.

The current distrubution on said (full size) vertical is one quarter of
the
wave of 360 deg. which would make it 90 degrees. Max current is at the
base
and then diminishes towards the tip in the cosine function down to zero.
Voltage distribution is just opposite, min at the base, feed point and
max
at the tip. EZNEC modeling shows that to be the case too.
Is that right or wrong?

Right. Although the distributed capacitance can change the shape.

It can change the amplitude, but not the shape of the current distribution
curve, that is the maximum is at the feed point (zero reactance - resonance)
and zero at the tips and follows cosine function.

If we stick them end to end and turn horizontal, we get dipole, which
then
would be 180 deg. "long" or "180 degrees resonant".
If not, what is the right way?

Right.

If I insert the coil, say about 2/3 up (at 5 ft. from the bottom) the
shortened vertical, I make the coil size, (inductance, phys. dimensions)
such that my vertical will shrink in size to 8 ft tall and will resonate
at
7.87 MHz.
I learned from the good antenna books that this is still 90 electrical
"resonant" degrees.
Maximum of current is at the feed point, minimum or zero at the tip.

What "good book"? It would help to see the context.

Say ARRL Antenna Book, 20th edition, page 16-7, Fig 10
Shows lengths h1 and h2 expressed as 15 deg. eaach.

None of my engineering books use electrical degrees except to describe
overall antenna height or length.

But that relates to describing the antenna properties in relation to
resonant frequency for that particular radiator.

They might say "60 degree top loaded resonant radiator" but they don't
say "60 degree tall radiator 90 degree resonant".

If you stick the coil at the base in series with radiator and bring it to
resonance (zero reactance at the frequency of interest) what "degree
resonant" will than radiator become, if not 90? ("Measured" from the feed
point, through the coil and then straight radiator.)

There might be a correct context, but I can't think of one off hand. So
I need an example from a textbook.

If you stick those verticals (resonant) end to end and horizontal, you
get
shortened dipole, with current distribution equal to 180 degrees or half
wave. Max current at the feed point, minima or zero at the tips.
(RESONANT
radiator)

The current distribution would not be the same as a half wave, becuase
the antenna is not 1/2 wave long.

Well, is 180 degrees half wavelength or not? Is the current maximum at the
feedpoint (center) and zero at the end, or not? The current distribution is
not the same, but is exhibiting properties of resonant half wave dipole with
current max at the center and zero at the tips. The shape is not the smooth
continuous cosine curve as in straight dipole, but affected by the loading
coils (drops) in their place (subject of disagreement).

Can we describe "pieces" or segments of the radiator as having
proportional
amount of degrees corresponding to their physical length, when excited
with
particular frequency?

Yes. It works fine for length. It does NOT work for loading inductors,
it does not work for short antennas which have anything form a uniform
distribution to triangular distribution, or any mix between including
curves of various slopes.

Why not? What happens to cosine current distribution curve when we insert
the loading element (inductance, coil, loading stub, resistance) in the
radiator? What formula applies to get the uniform or triangular
distribution? Can you show some mathematics?
So we have resonant standing wave element, that has current max at the
feedpoint and zero at the tip, which gives us 90 degree (or 180 with dipole)
or quarter wave distribution from the base to the tip. (reality) We can
express the straight pieces of radiator in degrees, but not the coiled up
piece that the wave has to go through?
The "uniform" and "triangular" distribution was used for approximation or
simplification of showing the current distribution in short loaded
radiators, while they are in reality segments of the cosine curve belonging
to length of the straight portions of the radiator. EZNEC shows that, when
you magnify the curve you can see there are no uniforms or triangles but a
cosine curve.

A 30 degree tall antenna with base loading simply has power factor
correction at the base, provided the inductor is not a significant
fraction of a wavelength long. It is a 30 degree base loaded radiator,
not a 90 degree antenna. And the inductor is not 60 degrees long.

We are not talking here about base loaded radiator. No detours please.
So how many electrical degrees has the quarter wave resonant radiator that
is loaded with loading coil (or stub) about 2/3 way up and is say 30 deg.
physical "length" to make it resonant?

73 Tom


73 Yuri, K3BU