"Tdonaly" wrote in message
...
Steve's info will get you a beginners understanding of circuit
theory

That WAS the intent.


which is based on a low-frequency, quasi-static simplification
of electromagnetic theory.

Yikes! Call it what you like.

Unfortunately, anything that has any
appreciable length, such as a transmission line or an antenna...
wave mechanics to get any real idea of what is happening
in these situations.

I guess you can call it "wave mechanics" if you like, but it IS true
that what happens on a transmission line is waves and this is quite
different from simple circuit theory. First you need the circuit theory,
though.


That isn't the end of it, though, since in order
to understand what is happening when an object radiates, you
have to understand Maxwell's equations....vector calculus.

This I'll disagree with. It's been so long since I studied
Maxwell's equations, I can't even spell his name, but I can give a workable
explanatin of radiation that the beginner can understand and won't cause
trouble for any ham's purposes. Will it violate old Maxwell? I don't know
and don't care for my purposes and 90% of the people interested.


That isn't the
end, either, but it's as close as any *normal* human wants to go.

Whew! sure glad I'm *abnormal*.


Whenever someone who was taught circuit theory tries to
apply its vocabulary and concepts to explain all electromagnetic
phenomena, that someone is going to run into trouble and
come up with a multitude of idiocies for which which he'll find no end of
people ready to criticize him.

Whoa... Sure glad I'm not trying to do THAT!


This is the problem: Cecil and Yuri want to explain the current taper
through a long solenoidal coil using the vocabulary and concepts of
circuit theory rather than the difficult but more precise
language of electromagnetic theory.

Sure glad I don't care and that I didn't tack my post onto theirs
thus indicating that I was trying to enter that discussion.


73 Steve--
Steve N, K,9;d, c. i My email has no u's.

Well, then there's that too..

-- (:-)
Steve N, K,9;d, c. i My email has no u's.

"Butch" wrote in message
...
Time out!! You people are taking all this far to seriously. Just throw
an aerial out the window, feed it to your rig via a tuner, and enjoy
Amateur radio.

Butch Magee KF5DE

Tdonaly wrote:
Steve's info will get you a beginners understanding ...
...quasi-static.
...electromagnetic theory. ...
...wave mechanics...
...Maxwell's equations....
...vector calculus.
...any *normal* human...
...multitude of idiocies
...no end of people ready to criticize him.

Oh yea! that too... I forgot "Maxwell"
--
Steve N, K,9;d, c. i My email has no u's.


"Ed Price" wrote in message
news:YFmZb.5138$C21.2768@fed1read07...

"Butch" wrote in message
...
Time out!! You people are taking all this far to seriously. Just throw
an aerial out the window, feed it to your rig via a tuner, and enjoy
Amateur radio.

Butch Magee KF5DE


It just not that simple, Butch.

I'm sure you have heard that Ham radio is a hobby that has many facets;
construction, public service, contesting, field trips, QRP DX, etc. Some
of
our members get their kicks merging theory with rag chewing. I don't think
there's any structure to this sub-category, other than to require at least
one mention of Maxwell in every discussion.


Ed
WB6WSN

Peter, K1PO wrote:
"Oliver heaviside was a poor kid from the London slums who had to go out
to work at age 16 and never saw the inside of a college or university."

I am aware of Heaviside`s story. He was the idol of one of my professors
who frerquently regaled us with heaviside stories, so he became one of
my favorites too.

Maxwell is not diminished by his advantages. He had the mathematical
background he needed to formulate his equations and the moxie to
speculate that displacement current generates a magnetic field same as a
conduction current does. This is the secret of radiation. Heaviside was
able to improve on the calculus, and simplify and reorganize Maxwell`s
work. Michael Faraday discovered electromagnetic induction and deserves
a lot of credit too. Everybody benefits from the work of others in
complicated fields. Faraday lived 1791-1867. Maxwell lived 1831-1879.
Heaviside lived 1850-1925. This really was during a golden age for the
British.

I had the Maxwell`s equations course many decades ago. Strangely enough,
it was titled "Ultra High Frequency Techniques". You really had to read
the syllabus to know what the course was about.

Best regards, Richard Harrison, KB5WZI

Jerry Martes wrote:
"I have never been convinced that "impedance" is the ratio of force to
response in any media."

Jerry framed the question very nicely.

The logic seems simple. More force is required when resistance to change
is higher. When current is very small despite high force, it must be due
to high resistance.

Resistance proportional to force (volts) and inversely proportional to
current (amps) seems perfectly logical to me. R=E/I

Best regards, Richard Harrison, KB5WZI

Art, KB9MZ wrote:
"The dipole is a very inefficient radiator."

Kraus, unfortunately, wasn`t one of my books until recently. I don`t
have the words memorized or know where they appear as I do with some of
Terman.

I seem to remember Kraus saying 95% efficiency was not unusual as a
dipole efficiency. As there are so many variations, it`s like a baseball
statistic, there must be a statistic that fits somewhere.

In any case, "efficient" is only as compared with similar devices.
Recall that dBd is the norm as an isotropic antenna is only a
theoretical creature. Catalogs are filled with antenna characteristics
as compared with a 1/2-wave dipole in free space. It is the standard of
comparison. It could hardly be correctly called inefficient.

Best regards, Richard Harrison, KB5WZI

Yep!! Very Good Coffee!!!!!!!!!!!

Steve Nosko wrote:

Oh yea! that too... I forgot "Maxwell"

I just love it when those born in the slums of London even tho they went to
work when they were 16 they had enough smarts
to go head to head with the experts. It must be a result of the morning fog
from the river where one learns quickly what is real
and what is not. Going to work for a living
at 16 is not all that bad since it allows you to make personal decisions
that can benefit
before the onset of age makes it too late.
An East Ender
Art



"Peter O. Brackett" wrote in message
news
Richard:

Hmmm....

Impedance... let's give it its' proper due!

It was the self taught "electrician", and ultimately Fellow of the Royal
Society, Oliver Heaviside, FRS
[1850 - 1925] who was born in the London slums to a very poor family and
who
had never attended
any school beyond the age of 16 who was the person who coined, defined and
first used the terms
"impedance", "admittance", and "reactance".

Oliver Heaviside also gave us Maxwell's Equations in the form we now know
them. Maxwell
wrote his equations in the form of 22 separate equations using the arcane
method of "quaternions".
Heaviside simplified those 22 equations given by Maxwell down to the four
simple equations with
two auxilliary constituent relations that we now know and love.

James Clerk Maxwell was a Cambridge educated mathematician from an
affluent
and educated family.
Oliver Heaviside was a poor kid from the London slums who had to go out to
work at age 16 and
never saw the inside of a college or university!

Heaviside never appeared to receive the citation at the ceremony to which
he
was invited when he
was inducted as a Fellow of the Royal Society after he was duly elected to
that lofty title by the
greatest Scientists of the day.

"Impedance"... thank you Oliver!

--
Peter K1PO
Indialantic By-the-Sea, FL


"Richard Harrison" wrote in message
...
Steve Nosko wrote:
"Apparently, because of the way the big bang occurred, when we put a
voltage across a resistor current flows in a manner that we discovered
follows the equation called Ohm`s law."

Big bang? Ohm wasn`t around then. He lived 1787 to 1854. Ohm discovered
that current in an electrical resistance is proportional to voltage.

Resistance is the type of impedance (opposition to electrical current)
in which current is locked in step to the applied voltage.

The item called a resistor is the type of resistance that converts
electrical energy to heat energy.

Not all resistances are resistors. Some resistances don`t convert
electrical energy directly into heat. In these non-dissipative
resistances, current drop is in-phase with the applied volts, or voltage
dropped across the resistance is in-phase with current through the
resistance, but it does not cause energy loss. An example of lossless
resistance is the Zo or surge impedance of a transmission line. Zo is
caused by the distributed inductance and capacitance of the line, but
current in the line is in-phase with the voltage across the line. Zo is
the voltage to current ratio of the waves traveling in either direction
on the transmission line. Zo = volts/amps, yet converts no energy to
heat in the lossless line. Another example of lossless resistance is
"radiation resistance". This is the desired antenna load, so it is
hardly a loss. Loss in the wire, earth, and insulators of the antenna
are resistive loads which produce heat but don`t help the signal.

An ohm is the unit of resistance. It is defined at 0-degrees C, of a
uniform column of mercury 106.300 cm long and weighing 14.451 grams. One
ohm is the resistance which drops one voltt when a current of one amp is
passed through it.

Reactances are also defined by their volts to amps ratios (ohms). The
big difference is that reactance does no work and produces no heat.
Opposition to electrical current comes from delay required to store ard
retrieve energy to and from fields in and around the reactances. Current
lags the applied voltage in an inductance. At time = 0, no current flows
into an inductance, but rises exponentially from the instant of initial
energization. Current leads the applied voltage into a capacitance. At
time = 0, full current flows into a capacitance but voltage across the
capacitance is zero and rises exponentially from the instant of initial
energization.

In an a-c circuit, the current through an inductance lags the voltage by
90-degrees. In a a-c circuit, the current through a capacitance leads
the voltage by 90-degrees. Phase shifts are produced by energy storage
in reactance. There is no phase shift in a resistance. No electrical
energy is stored in a resistor, but its matter does have a thermal
capacity. Once its atoms are agitated by heat their inertia is evident
in the resistance`s temperature. It takes time to cool.

Steve wrote: "Things get all messed up."

As old Carson Robinson sang: "Life gets tedious, Don`t it?" Steve gave
the formulas for capacitive and inductive reactances. They have always
seemed convenient to me. Steve says: "---we call this new kind of
(corrupted) resistance "Impedance"."

No. Impedance is the general name for opposition to electricity.
Resistance is the specialized name for the case in which the impedance
alone causes no delay and stores no electrical energy. All electrical
impedance is defined by its voltage to current ratio, and is the total
opposition (resistance and reactance) a circuit offers to the flow of
electricity. For d-c, reactance doesn`t count. For a-c, total opposition
consists of the vector (phasor) sum of resistance and reactance in a
circuit. Impedance is measured in ohms and its reciprocal is called
admittance. The symbol for impedance is Z. The symbol for admittance is
Y.

Steve also writes:
"Poof! BUT converts it into radio frequency energy (RF) also called an
electromagnetic field or wave."

Yes. A radio wave is r-f energy which has escaped the confines of wires
and doesn`t come back. Whenever wires in open space carry high-frequency
current, some energy gets away as a radiated field, having a strength
that varies inversely with the distance.

Best regards, Richard Harrison, KB5WZI

On Fri, 20 Feb 2004 14:34:46 -0600 (CST),
(Richard Harrison) wrote:
Art, KB9MZ wrote:
"The dipole is a very inefficient radiator."

.... It could hardly be correctly called inefficient.

Hi Richard,

We are back into this stale wheeze about efficiency "per unit length"
which is the same siren song of the cfa.

Put one out in the field, measure it against one of those "inefficient
radiators" and we find it roughly -30dB more "efficient" than the
standard BCB antenna.

The cfa may well be more efficient "per unit length" because it costs
less in steel and is smaller, its coverage follows that downward
spiral too. On those terms, hoisting a dummy load 30 feet into the
air would be far more efficient "per unit length" with roughly -60dB
more "efficiency."

Properly speaking, this new usage of "efficiency" should have been
confined to the thread Semantic Nonsense where we could properly
appreciate the ratio:

Semantic Nonsense + Nonsense
--------------------------------------
Nonsense

As any adept calculator puncher can appreciate, almost anything said
shows more than 100% efficiency. :-)

The acid test of the capitalist broadcast marketplace has shown not
one cfa sold. Now, in the socialist world, like Egypt, they had one
(1) provisional sale? If there were still an Iron Curtain, they would
have bought this nonsense up like Pravda at the red square newsstands.
Even at that, the Iron Curtain would probably be a necessary
resonating structure to make it work.

73's
Richard Clark, KB7QHC

Richard Harrison wrote:

Art, KB9MZ wrote:
"The dipole is a very inefficient radiator."

I seem to remember Kraus saying 95% efficiency was not unusual as a
dipole efficiency.

I don't think that's the efficiency that Art is talking about. Art's
efficiency seems to be defined as the power delivered to the receiver
divided by the power sourced by the transmitter.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----