A little more on missing degrees
 

"Richard Fry" wrote in message
...


An antenna * system * does not need to have X number of degrees to be
resonant. It only needs to have ~zero reactance at its feedpoint --
which, for electrically short AND long radiators can be achieved by use of
a suitable matching network.

Such networks don't add or subtract electrical degrees, however. They
only reduce/cancel the natural reactance of the physical radiator in use.

RF

The above post is without doubt, the clearest, cleanest and to the point
statement of any made to date in this whole silly chain of posts! It
demonstrates a clear and firm grasp of antenna theory. Something that is so
obviously missing from 99 percent plus of the bulk of posts on the subject!

Dean -- W4IHK

A little more on missing degrees
 

Dean Craft wrote:
The above post is without doubt, the clearest, cleanest and to the point
statement of any made to date in this whole silly chain of posts! It
demonstrates a clear and firm grasp of antenna theory.

A self-resonant coil is obviously 90 degrees long. If one
removes 5% of the turns and replaces them with a stinger
to bring the system back to resonance at the same frequency,
do you really believe the coil has magically changed from
90 degrees long to zero degrees long?
--
73, Cecil http://www.qsl.net/w5dxp

A little more on missing degrees
 

"Cecil Moore"
A self-resonant coil is obviously 90 degrees long.
_____________

A coil is not the electrical equivalent of a linear, physical, ~90-degree,
self-resonant radiator. How well do you expect your self-resonant coil to
radiate?

When you add a stinger to a coil, it is the stinger that radiates the great
majority of the applied power. The coil just makes it possible/practical
for the tx to supply r-f power to that antenna system that the stinger CAN
radiate, by improving the Z match between the source and the feedpoint.

RF

A little more on missing degrees
 

Dean Craft wrote:

SNIPPED

The above post is without doubt, the clearest, cleanest and to the point
statement of any made to date in this whole silly chain of posts! It
demonstrates a clear and firm grasp of antenna theory. Something that is so
obviously missing from 99 percent plus of the bulk of posts on the subject!

Dean -- W4IHK



Dean, maybe we can start a discussion about the missing 1%

"Something that is so obviously missing from 99 percent..."

A little more on missing degrees
 

"Dave" wrote in message
. ..
Dean Craft wrote:

SNIPPED

The above post is without doubt, the clearest, cleanest and to the point
statement of any made to date in this whole silly chain of posts! It
demonstrates a clear and firm grasp of antenna theory. Something that is
so obviously missing from 99 percent plus of the bulk of posts on the
subject!

Dean -- W4IHK



Dean, maybe we can start a discussion about the missing 1%

"Something that is so obviously missing from 99 percent..."


I have all but given up on that possibility. If its not heated immature
school yard rhetoric driven by obvious professional jealousy, then its mind
playing games just as has appeared since my earlier post. The troll effect
all too frequently takes over and destroys any serious chain of thought.

Dean -- W4IHK

A little more on missing degrees
 

I gave up on the 'missing degrees' and all variations topic about 1
month ago. Hit the KILL Button and read on!

Dean Craft wrote:

"Dave" wrote in message
. ..

Dean Craft wrote:

SNIPPED

The above post is without doubt, the clearest, cleanest and to the point
statement of any made to date in this whole silly chain of posts! It
demonstrates a clear and firm grasp of antenna theory. Something that is
so obviously missing from 99 percent plus of the bulk of posts on the
subject!

Dean -- W4IHK



Dean, maybe we can start a discussion about the missing 1%

"Something that is so obviously missing from 99 percent..."



I have all but given up on that possibility. If its not heated immature
school yard rhetoric driven by obvious professional jealousy, then its mind
playing games just as has appeared since my earlier post. The troll effect
all too frequently takes over and destroys any serious chain of thought.

Dean -- W4IHK

A little more on missing degrees
 

Richard Fry wrote:
"Such networks don`t add or subtract electrical degrees, however. They
only reduce/cancel the natural reactance of the physical radiator in
use."

True if the only mismatch is reactance. A too-long antenna can be
electrically shortened for matching purposes by tuning it to resonance
with the proper series capacitance. A too-short antenna can be
electrically lengthened for matching purposes by tuning it to resonance
with the proper series inductance.

Reactance varies quickly near the resonant length. Radiation resistance
varies more slowly tending to increase at a steady rate as the antenna
is lengthened.

What radiates is current in a length of antenna. What gets current into
an antenna is a conjugate match. Reactance is zeroed out, and source and
load resistances are matched. That`s what`s needed for maximum power
transfer between generator and antenna.

Analysis may have been more abundant than needed for practical purposes.

The velocity of current through a coil has been disputed. Some said it
was almost instantaneous. That was new to me. The nature of inductance
is to produce counter emf which by Lenz`s law opposes current into an
inductance and temporarily delays current changes in an inductance. Only
in a pure resistance is there instantaneous correlation between voltage
and current.

It is believed that the speed of light "c" is a speed limit on
electromagnetic waves. An action in one place must have a delayed
response elsewhere depending on distance.

I can imagine a wave launched at one of an inductor sweeping across its
length and ignoring the round and round path of the wire, but I don`t
know of any of the old authors in my collection who say that such a
short-cut happens. Conductors are the source of free electrons which
permit current flow and my experience is that electricity goes where it
is wired.

Best regards, Richard Harrison, KB5WZI

A little more on missing degrees
 

Richard Fry wrote:
"Cecil Moore"
A self-resonant coil is obviously 90 degrees long.

A coil is not the electrical equivalent of a linear, physical,
~90-degree, self-resonant radiator. How well do you expect your
self-resonant coil to radiate?

Not very well. Nobody is saying that a coil is a good
radiator. It probably radiates about as much RF as a
piece of wire of the same axial length as the coil.

Nothing about the discussion of phase
shift through a coil has had anything to do with radiation.
In fact, I have ignored radiation from the coil in all
of my calculations since I consider it to be negligible.

We have a phase shift in a transmission line with negligible
radiation. The same is true of a loading coil.

When you add a stinger to a coil, it is the stinger that radiates the
great majority of the applied power.

Absolutely no question about that. The round and round
design of a coil makes it more akin to a piece of
transmission line than it does to a radiator. But like
a transmission line stub, it contributes a phase shift
to the system.

The stub on a properly designed J-Pole doesn't radiate
much either. But one can certainly calculate the phase
shift from the feedpoint to bottom of the radiating element.

Again, the phase shift in the coil has virtually nothing
to do with how much the coil radiates. Looking at just
one turn on the coil, the current on each side of the
turn is approximately equal magnitude and flowing in
opposite directions (just as in a transmission line).
So virtually all the radiation is canceled by the
opposite near fields (just as in a transmission line).
--
73, Cecil http://www.qsl.net/w5dxp

A little more on missing degrees
 

Richard Harrison wrote:
I can imagine a wave launched at one of an inductor sweeping across its
length and ignoring the round and round path of the wire, but I don`t
know of any of the old authors in my collection who say that such a
short-cut happens. Conductors are the source of free electrons which
permit current flow and my experience is that electricity goes where it
is wired.

Consider a tank circuit link coupled to the outside world.
There are probably negligible free electrons flowing from
primary to secondary. Yet efficient energy transfer occurs
when the coils are tightly coupled.

In a loading coil, each turn is tightly coupled to the
adjacent turn causing part of the current to be the result
of the fields rather than wire path. That's why the VF of
the loading coil is roughly double what it would be for
"round and round the coil" calculations. The VF for a 75m
bugcatcher coil appears to be in the ballpark of 0.04 which
is a far cry from the straight across 1.0 or even 0.5
--
73, Cecil http://www.qsl.net/w5dxp

A little more on missing degrees
 

Dave wrote:
I gave up on the 'missing degrees' and all variations topic about 1
month ago. Hit the KILL Button and read on!

For those who didn't give up, here is a summary of what I
was able to do with EZNEC. This exercise should be able
to be repeated in the real world.

1. Using the helix feature of EZNEC, I created a 100 turn
octagonal coil, 6 inches in diameter, 4 turns per inch.

2. I installed it as a base loading coil over a mininec
ground plane and removed turns until it was self-resonant
on 4 MHz. That left a total of 69 turns on a 1.435 foot
long coil. Give that the coil is 90 degrees at the self-
resonant frequency, I calculated a velocity factor of
0.023 for the coil.

3. The coil was then trimmed to half size, i.e. 34.5 turns.
Assuming it was then 45 degrees long, the Z0 was determined
to be approximately 2200 ohms by looking at the feedpoint
impedance reported by EZNEC. 45 degrees from 0-j0 on the
Smith Chart is at -j1.0.

4. A stinger was added to the above 45 degrees of coil to
bring the antenna back to resonance on 4 MHz. It took 7 ft.
of stinger, or 10.2 degrees. 10.2 degrees from 0-j*infinity
on the Smith Chart is at -j4.8.

5. The ratio of -j4.8/-j1.0 is the ratio of the Z0 of the
coil to the Z0 of the stinger. If the Z0 of the coil is
indeed 2200 ohms, the Z0 of the stinger is 458 ohms, just
about where it should be. The impedance discontinuity
provides the "missing" ~35 degrees of the antenna.

6. Using Dr. Corum's equation for velocity factor yields
0.02 for that coil, a value 13% lower than the one
predicted by EZNEC, well within the ballpark for
expectations.

My conclusions: The delay through a loading coil is in
the tens of degrees. The delay through the elements of
the antenna do not add up to 90 degrees. In the above
EZNEC example, the delay from feedpoint to the tip of
the antenna is only 55 degrees. The "missing"
degrees are provided by the impedance discontinuity
between the coil and the stinger. There is no real-
time delay associated with those "missing" degrees.
--
73, Cecil http://www.qsl.net/w5dxp