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

On Thu, 23 Mar 2006 11:12:54 -0500, "Yuri Blanarovich"
wrote:

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.

Hi Yuri,

At your page you assert:
"The current in a typical loading coil in the shortened antennas
drops across the coil roughly corresponding to the segment of the
radiator it replaces. "
so I must presume this is part and parcel to your question above and
the coil is part of that proportionality where all segments combine to
90°.

On the other hand, Cecil is only willing to allow:
On Wed, 22 Mar 2006 23:48:11 GMT, Cecil Moore
wrote:
+/- 50% accuracy.

Now, given that you might describe a radiator whose vertical sections
add to 30°, then it follows from your page's assertion that the coil
must represent 60°. Cecil, again, would give pause and restrict that
to some value between 30° and (oddly enough) 90°. The total structure
then represents a 60° to 120° electrically high verticle.

The long and short of this (a pun) is that Cecil has argued you into a
rhetorical corner where it is highly unlikely that the whole shebang
is ever 90° long - by parts that is. Or as a Hail Mary argument, you
could simply assert that the range encompasses the right value for
your assertion above, but then anyone could use the same logic to say
all loaded antennas are only 70° electrically tall and another could
boast 110° and you couldn't dispute them. (Yes, you could, of
course, this is a newsgroup afterall.)

Perhaps you would like to argue this for yourself (I don't pay much
attention to Cecil anyway as this +/- 50% slop factor accounts for).

73's
Richard Clark, KB7QHC

Richard and everybody,

Let's try again from scratch, fresh, I will try to go step by step, so there
are no ambiguities, twists and turns to each own's la-la land.

Cecil is on well deserved break, so I am am on my own, stuck on whatever it
might be.

I will not continue, unless there is an agreement at each point, I go
sloooow, for the benefit of mine and others who duntgetit.
The "camp" think is to signify two groups claiming the different behavior of
the current in the antenna loading coil. No intent to punish anyone.

Please go to the new thread that I started.
"Current across the antenna loading coil - from scratch"
If needed I will post pictures on my web site, unless there is a way to do
it here.

Thank you!

Yuri, K3BU.us

This thread belongs back in the original place, so it flows in context.

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.

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.

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.

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.


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?

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?

Right.

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.

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.

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

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

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.

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.

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.

73 Tom