Yuri Blanarovich wrote:

So what is it then you claiming being equal.

In a loading coil with very small distributed capaciatnce to the
outside world compared to termination impedance, current has to be
equal. Phase shift in current at each end has to be nearly zero.

This is true for ANY antenna length or loading coil location.

This is what everyone was saying.

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.

One group is saying the distributed capacitance of the inductor to the
outside world controls the distribution, another group appears to be
saying it is a function of electrical degrees the coil makes up.

I agree with the majority of people posting in these threads. It is the
capacitance from the coil to the outside world that controls current
distribution in the inductor and produces and phase difference in
CURRENT at each end. If you look at Reg, Ian, Roy, all the Toms, Gene,
Richard Clark, and on and on we are all saying that same thing.

Richard Harrison, Yuri, and Cecil seem to argue against that, but that
is how ANY inductor behaves. It can be proven to behave the way most
people are trying to explain.

The coil does NOT represent the "missing degrees". It does NOT have to
have current taper (as a matter of fact a good indictor and antenna
design won't show any significant current taper).


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.

The current distribution in an antenna is primarily a function of
displacement currents caused by capacitance to the outside world and
series impedance. If I have a short small diameter whip of uniform
cross section, it has triangular distribution.

If I sufficiently end-load the very same antenna with no change in
length, the current distribution becomes close to uniform. The thinner
the elenment and larger the end loading, the more uniform the current.

This is why radiation resistance is someplace around FOUR times greater
in an end-loaded antenna when compared to a base loaded antenna of the
same height. Radiation resistance is tied to ampere-feet, and
ampere-feet is larger with end loading rather than base loading.


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.

That does not say 90 degrees. It says 15 degrees.

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.)

It is resonant. It is 15 degrees tall.

It is NOT 90 degree resonant.

Degrees of height is a distance measurement, not an electrical
parameter. If someone is using it to describe resonance thay are
misusing the term.

I can have a 180 degree long resonant dipole.

I can have a 20 degree long resoannt dipole.

I cannot have a 180 degree resonant dipole that is 20 degrees long. I
cannot have a 15 degree tall vertical that is 180 degree resonant, or
90 degree resonant. That argues against itself.


Well, is 180 degrees half wavelength or not?

Yes, 180 degrees is 1/2 wave.

Is the current maximum at the
feedpoint (center) and zero at the end, or not?

Yes.

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).

So what? The degrees are a measure of physical length. A 20 degree long
coil loaded dipole is a 20 degree long resonant dipole. It is not a 180
degree resonant antenna.

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?

This has all been explained over and over again. You can also see it in
any engineering book. ON4UN's book initially had it wrong, but it is
corrected now.

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)

No, it does not. 90 degrees when used with antennas is a measure of
distance as it relates to frequency. You can't have a 15 degree long
antenna that is "180 degree resonant", and the current distribution
depends on distributed capacitance and series impedance.

We can
express the straight pieces of radiator in degrees, but not the coiled up
piece that the wave has to go through?

Right. You cannot build a "60 degree coil to make my 30 degree antenna
90 degrees long".

Think about it. If the coil was 60 degrees long, you could move it
anywhere in the antenna and it would be resonant at the same frequency!

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.

Oh, we are picking nits now. In this case we have to get every
engineering book to say "it is such a small portion of a curve it looks
straight" instead of using triangular or uniform.

After all current might be 1.0001 amperes at one point and 1.0000
amperes ten feet away, so I guess that is actually not uniform if we
pick the nits enough.

The cosine shape is not true as a rule, however. That shape depends on
distributed capacitance being uniform.

We are not talking here about base loaded radiator. No detours please.

If your theory does not cover base, center , and top loading it is
incomplete, If it does not treat a coil as a coil no matter how it is
used or set limits, it is incomplete.

Base loaded, center loaded. It doesn't matter.


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?

That's already been explained. If it is 30 degrees tall, it is a
resonant 30-degree tall radiator.

It is not a "90 degree resonant 30 degree tall radiator with a 60
degree coil".

73 Tom