Current across the antenna loading coil - from scratch
 

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

Let's start the fresh thread and trace step by step where I went wrong.

Just reminder that we are talking typical situations, as for example real 40
m (or 80 m) mobile whip with loading coil about 2/3 up the radiator. We are
talking about resonant electrical quarter wave monopole. We are talking
about standing wave RF current that can be measured with RF ammeter and is
shown and plotted in modeling programs like EZNEC.

Here we go:

wrote in message
Let's focus on one thing at a time.

You claim a bug cather coil has "an electrical length at 4MHz of ~60
degrees". That concept is easily proven false, just like the claim a
short loaded antenna is "90-degree resonant". Both can be shown to be
nonsense pictures of what is happening.

Assume I have a 30 degree long antenna. If the loading inductor is 60
electrical degrees long, I could move it anyplace in that antenna and
have a 90 degree long antenna.

We all know that won't happen, so what is it you are really trying to
say?

73 Tom


OK lets get me some educating here.
I understand that, say quarter wave resonant vertical (say 33 ft at 40m) has
90 electrical degrees.
Is that right or wrong?

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?

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?

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.

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)

How many electrical degrees would that make? How do you arrive at that?
Why is this a nonsense?

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?

If I can be enlightened about this, we can go then to the next step.

Answers, corrections please.

Yuri, K3BU

Current across the antenna loading coil - from scratch
 

On Thu, 23 Mar 2006 12:50:32 -0500, "Yuri Blanarovich"
wrote:

Let's start the fresh thread and trace step by step where I went wrong.

Hi Yuri,

Are you then abandoning your web page?

You know, it would seem to be better effort to stick with the
demonstrables there and to make sense of them, than to wander the
intellectual landscape of "theory."

OK lets get me some educating here.
I understand that, say quarter wave resonant vertical (say 33 ft at 40m) has
90 electrical degrees.
Is that right or wrong?

If you cannot define your limits of error, then Cecil is bound to do
it for you and plug in +/- 50% to make any assertion laughable, such
as:

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?

You've left too many things out to agree to more than a rather
insubstantial maybe. If that's sufficient, then there's really no
need to go any further, is there?

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

Yuri wrote,

" 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.
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'm not sure who all you put in W8JI's "camp," but I'm absolutely sure
that I've read recent postings by W8JI himself that affirm that there
can be significant difference in current between the ends of the
loading coil. What I DO see him posting is that if the difference is
large, the antenna design is almost certainly suboptimal.

If you want to understand how a loading coil with zero capacitance to
the outside world can actually work, I suggest you read the Joseph
Boyer article from "Ham Radio" magazine some 28 years ago. Ian White
gave a more complete reference to that article in one of his postings
in the interminable thread. I'm always happy to ship out a copy of
that article for the cost of postage.

Cheers,
Tom

Current across the antenna loading coil - from scratch
 

Yuri, you have neglected at least one important unit of measu namely,
the action integral of the 'active antenna' times the current
[ampere*degrees].

For simplicity, assume a constant one ampere is flowing in a physical 15
degree antenna. The answer is 15 ampere*degrees. In a true 1/4
wavelength antenna the answer is 90 ampere*degrees. The shortened
antenna is [=] a tuned 15 degree antenna NOT a 90 degree antenna!!

In a real shortened antenna, the base current may be assumed, to a first
approximation, as constant from the base to the loading coil. If that
portion of the antenna is 10 degrees, then 10 ampere*degrees is the
action integral.

The current in the top section can be assumed linear from the value at
the top of the coil to the tip where I=0. This is a triangle [or a sin
function that is close to linear] that can solve to two possible values.
The first is based on one ampere exiting the top of the coil and the
solution is 1/2*1 ampere*5 degrees = 2.5 ampere degrees. The second is
based on a sinusoidal distribution from the tip to the 5 degree point at
the top of the coil where the current is 0.087 ampere. [The sin of 5
degrees is 0.087.] So, the action integral is 1/2*0.087 amperes*5
degrees = 0.218 ampere*degrees.

The practical application deals with the efficiency of the antenna. Is
that tuned 15 degree long antenna a 12.5 ampere degree antenna; or, is
it a 10.218 ampere degree antenna? [That's approximately a difference of
1 dB in antenna performance.]

The discussion here for the past three infinities is: What is happening
inside the tuning coil? Is there a change in current amplitude? If so,
please explain the physics. Is there no change in current amplitude? If
so, please explain the physics.

The coil is physically less than one degree in length, but contains
enough wire to be a significant portion of a wavelength. Interwinding
capacitance and distributed inductance can make the coil look like a
transmission line.

The flux density from each turn in an air core coil construction
diverges as one progresses along the coil [the flux density at turn #2
is higher than at turn #60 for example]. Restated, there is a leakage
inductance along the coil. The flux density has a propagation time in
free space of approximately 0.5E-9 seconds. Is this significant? [I
don't think so]

In the tuning coil there exists an interwinding capacitance and a
capacitance to "structure" [whatever that is].

In 1958, my college days, we were instructed to ignore the coil and
solve the antenna as two separate sections with an infinitesimal gap at
the junction. I never liked that model then and I don't like it today!
[It still allows two solutions][We were instructed that the current is
constant].

So, we have two well entrenched positions: the current does not change
in the coil, and, the current changes in the coil. Like World War I, it
is trench warfare with much bloodshed [reputation] on both sides.

Due to leakage inductance, I suspect that the current does change within
the air core coil but the change is much less than that implied by the
simple sin wave distribution [sin 5 degrees] used above.

Below the coil the H field dominates. Above the coil the E field
dominates. The transition from E to H occurs across [within] the coil.
That leads me to conclude that there is a change of current within the
coil.

In any event, the 15 degree antenna is still a 15 degree antenna! The
question is: what about that 1 dB difference in the modeling analysis?

This simple engineer is still unconcerned about one dB difference and
it's impact on antenna gain. If the science side of this discussion
can't agree, then I'll simply continue to operate mobile and not worry
if my signal is one dB stronger or weaker at the receiving end of the
path!! It is what it is!!

# # #

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.
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.
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.

Let's start the fresh thread and trace step by step where I went wrong.

Just reminder that we are talking typical situations, as for example real 40
m (or 80 m) mobile whip with loading coil about 2/3 up the radiator. We are
talking about resonant electrical quarter wave monopole. We are talking
about standing wave RF current that can be measured with RF ammeter and is
shown and plotted in modeling programs like EZNEC.

Here we go:

wrote in message

Let's focus on one thing at a time.

You claim a bug cather coil has "an electrical length at 4MHz of ~60
degrees". That concept is easily proven false, just like the claim a
short loaded antenna is "90-degree resonant". Both can be shown to be
nonsense pictures of what is happening.

Assume I have a 30 degree long antenna. If the loading inductor is 60
electrical degrees long, I could move it anyplace in that antenna and
have a 90 degree long antenna.

We all know that won't happen, so what is it you are really trying to
say?

73 Tom



OK lets get me some educating here.
I understand that, say quarter wave resonant vertical (say 33 ft at 40m) has
90 electrical degrees.
Is that right or wrong?

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?

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?

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.

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)

How many electrical degrees would that make? How do you arrive at that?
Why is this a nonsense?

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?

If I can be enlightened about this, we can go then to the next step.

Answers, corrections please.

Yuri, K3BU

Current across the antenna loading coil - from scratch
 

Dave wrote:
. . .
The practical application deals with the efficiency of the antenna. Is
that tuned 15 degree long antenna a 12.5 ampere degree antenna; or, is
it a 10.218 ampere degree antenna? [That's approximately a difference of
1 dB in antenna performance.]
. . .

I believe you're comparing the field strengths from two antennas both
driven by the same current. If you drive them with the same power, a
more fair comparison, you'll find a negligible difference in field
strength. Efficiency is another issue, solely related to losses in the
antennas. Without knowing what those losses might be, we can't say
anything about the relative efficiency. In practice it'll probably be
extremely closely the same also.

Roy Lewallen, W7EL

Current across the antenna loading coil - from scratch
 

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

Current across the antenna loading coil - from scratch
 

On Sun, 2 Apr 2006 22:54:10 -0400, "Yuri Blanarovich"
wrote:

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.)

Hi Yuri,

This must be a convention that is particular to only a very few Hams.
The FCC database describes AM antennas in both electrical and physical
height as follows.

WGOP 80.00° tall 125.2 meters tall 540 kHz
WWCS 63.50° tall 98.8 meters tall 540 kHz
WFTD 79.00° tall 64.0 meters tall 1080 kHz
KYMN 118.60° tall 92.3 meters tall 1080 kHz
WWLV 90.00° tall 47.2 meters tall 1620 kHz
WTAW 204.00° tall 106.7 meters tall 1620 kHz

There may be some discrepancy, but it certainly looks like antenna
specification is by the electrical equivalent of the physical height
(and whatever l/d fudging) and with only one happening to be 90°.

Further, given most references (for professionals) is aimed at a
common specification that is largely driven by this agency, it would
seem odd to step out of this expectation to change to calling all
antennas 90° simply because they resonate.


http://www.fcc.gov/mb/audio/amq.html

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

On Sun, 2 Apr 2006 22:54:10 -0400, "Yuri Blanarovich"
wrote:

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?

Hi Yuri,

This is thin ice. If you are treading along the 1:1 replacement of
coil (wire-length/phase/Vf/whatever) for missing radiator length; then
Cecil is prepared to prove it to within ±59% error.

We could call it Cecil's 1.59:0.41 replacement rule - guaranteed to
prove just about anything, and to whiten your teeth.

73's
Richard Clark, KB7QHC

Current across the antenna loading coil - from scratch
 

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

Current across the antenna loading coil - from scratch
 

"Richard Clark" wrote
This must be a convention that is particular to only a very few
Hams. The FCC database describes AM antennas in both
electrical and physical height as follows. .... it would seem
odd to step out of this expectation to change to calling all
antennas 90° simply because they resonate.
_____________

The FCC data cited does not include the reduced velocity of propagation
along the radiator -- which means that an FCC "90 degree" radiator is not
resonant, it has some inductive reactance. A network is used at the
radiator feedpoint to transform the complex impedance there to properly
match the transmission line.

That "90 degree" radiator would need to be shortened by several percent in
order to be self-resonant. Kraus (3rd Ed, p 182) shows a feedpoint Z of 73
+ j42.5 ohms for a thin-wire, linear dipole that is a physical
1/2-wavelength, and that self-resonance occurs at a length a few percent
shorter, when the radiation resistance drops to about 65 ohms.

An unloaded 1/4-wave MW broadcast monopole working against the typical
broadcast radial ground system has about 1/2 the impedance that Kraus shows
for a dipole in free space.

RF