Hi Richard, TOP and internal posting...sorry folks.

I think you are learned on this subject and won't quibble about what
really happens in the real world. I think you know and I claim that I know.
I will, however pick a little bone in regards to the answer which I
posted to an email since I also thought would help others at a similar level
of understanding or confusion.

Oh geeze! here he goes...you had to set him off..
Here's my mantra and why a I am a little miffed by (but actually understand)
frequent attempts to correct my explanations.
The words we use and the depth to which we go at any given point to
describe things, have an effect on the ability of people to absorb the
concepts. As an instructor of basics, I have worked very hard, for a long
time, to understand and use effective ways to transfer an understanding of
electronic principles to students at what might be considered the lower
rungs of the technical ladder...the beginners...the hams also. There is
what I'll call an "instructor's high" associated with the light bulb going
on in a student. It's really cool.
I carefully craft my responses to the apparent level of knowledge of the
questioner. I do my best to form a coherent story which progresses from
simple, where a concept needed to understand more complex concepts is
explained first, without adding the unnecessary complications of true, but
potentially confusing facts, to the more complex goal I perceive to be the
questioner's goal. Once the basic concepts sinks in AND the student is
ready for the next level, usually by a response, I then proceed to build. It
is the old "speak to your audience" concept.
I don't dispute that your explanations are correct. They appear very
good, rather complete. I do believe however, that your most assuredly
honest and well meaning attempt to be correct, completely correct, actually
makes the subject more confusing to the beginner. I believe this because I
have been there. In fact, I must, almost every class session, throttle
myself from doing just the very same thing. Why? Because when I do, I have
succeeded in causing more confusion, resulting in a mental block to learning
which requires much more effort at damage control to erase the mental
blockage I created with my ignorant desire to be completely correct. Please
understand that I am being harsh on *myself* because I have been frustrated
by this and work hard to keep it under control. As an Engineer, teaching
technician students, one must keep in mind that there is a different state
of mind and ability to absorb what to them, appears a very complex
subject...but to my arrogant mind is really very simple. After all,
piecewise parametric polynomial interpolation looked like an impossible
concept, way beyond my comprehension back in 92 when I first saw reference
to it. Now, it looks like the simplest thing any high school Algebra
student can understand.

I'm also at a point in my life that I have seen and done so much in
this field (and it all seems so simple) that I wish to return some of it to
others, and I wish to do it very effectively.

Of course, now you're going to tell me that you also have been teaching for
x years and your methods are equally successful...so be it. There needs to
me more of us.

BTW...what is your line, Richard?

Some comments, corrections and whatever stuck my fancy about what you
wrote...


"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.

The concept I was trying to relate in a slightly 'light' manner was:
The stuff that happens, happens 'cuz of what we call "physics",
"physical laws" or "nature" or sump-in' like that, not because there is an
equation making it happen. Resistors don't know Ohm's law and don't conduct
current because of Ohm or his discoveries.

The equation we call Ohm's law is simply a model of how reality works.
Like a model airplane, which helps us understand what a real airplane looks
like. Ohms law, and all the other equations, help us understand what real
electronics "looks like".


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

A completely valid way to word it, but to a beginner I think the phrase
"locked in step " is vague. It would be a good start, but probably needs
expansion to explain what it means.



The item called a resistor is the type of resistance that converts
electrical energy to heat energy.
Not all resistances are resistors.

I wouldn't have worded it that way, but it (resistor is the type of
resistance) is a valid model to have in mind. That is, as a way to
distinguish it from "a resistance which is not a resistor". This made me
think of how I think of it.. and when I use the word "resistance" I think of
it as as a resistor, yet an impedance has a real or "resistive" part. That
word "resistance" for me conotes a "resistor" where the others conote the
other concept. Interesting nomenclature, that's all.

Some resistances don`t convert
electrical energy directly into heat. In these non-dissipative
resistances,

Well, here's where I'll say that I think this is truly a matter of
symantics. Your terminlolgy implies that dissipation = heat. I agree that
the most common usage it that "... is dissipated as heat...". However, this
next bit:
...is in-phase with current through the
resistance, but it does not cause energy loss.

I think has a symantics problem. I'm sure you truly understand what
happens, but the words "...does not cause energy loss." isn't correct,
because the energy IS lost from the circuit. The circuit "can't tell" the
difference 'tween the resistor and any other kind of resistive component.
It just may or may not be as heat, right?
You know what happens and I know what happens, but the OP didn't, so
I was starting him down a path that wouldn't paint him into a corner of not
being able to understand the other resistive types of things later...if so
desired.


An example of lossless
resistance is the Zo or surge impedance of a transmission line.

Again, the power IS lost from the source, no? I think this an important
basic understanding. To the sourse, it is gone. Poof! never to be seen
again. I think it is a good model to understand and helps go further
without Maxwell complicating things. I think you can go pretty far without
Maxwell (gee, twice in one paragraph) and still have a good amount of
(correct) sixth sense about what is going on in electronics and transmission
lines.


Zo is ... yet converts no energy to heat in the lossless line.

And my model didn't exclude this. I thought I was explicit about
that without bringing in more complexity for the OP.


"radiation resistance". ...is hardly a loss.

Again, as far as the transmitter circuitry is concerned, it is.


The following is a well done explanation which goes further and into
more detail...with one disagreement.

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.

No. In the context of my writing for someone who has an unserstanding
of DC and resistance, reactance it a very confusing factor. It corrupts an
otherwise simple world. Getting into Vector Algebra and phasors is a
significant step up in mathematics for the beginner not inclined to go the
Engineering route. What I'm saying is that although the unified field
theory may very well be the absolutely correct explanation of everything in
the universe, we don't need to explain it fully in the beginning to help
someone understand Gravity's acceleration, F=MA and you can't push a rope.
Newton certainly didn't need it. For all I know, F=MA may very well be a
special case in quantum mechanics, but I don't need it to calculate
accelerations, velocities, etc


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

Steve, I also tried to give back and taught at a junior college for a couple
of years but I found out that talking and communicating were two different
things. If what you do
succeeds in comunicating then you are doing good where others have failed by
resorting to just talking or handing out books. By you "communicating" you
encourage independent thought which is so much better than relying just on
memory and underlined quotes.
If you are winning then keep at it and disregard comments that are without
depth.
Cheers
Art

"Steve Nosko" wrote in message
...
Hi Richard, TOP and internal posting...sorry folks.

I think you are learned on this subject and won't quibble about what
really happens in the real world. I think you know and I claim that I
know.
I will, however pick a little bone in regards to the answer which I
posted to an email since I also thought would help others at a similar
level
of understanding or confusion.

Oh geeze! here he goes...you had to set him off..
Here's my mantra and why a I am a little miffed by (but actually
understand)
frequent attempts to correct my explanations.
The words we use and the depth to which we go at any given point to
describe things, have an effect on the ability of people to absorb the
concepts. As an instructor of basics, I have worked very hard, for a long
time, to understand and use effective ways to transfer an understanding of
electronic principles to students at what might be considered the lower
rungs of the technical ladder...the beginners...the hams also. There is
what I'll call an "instructor's high" associated with the light bulb going
on in a student. It's really cool.
I carefully craft my responses to the apparent level of knowledge of
the
questioner. I do my best to form a coherent story which progresses from
simple, where a concept needed to understand more complex concepts is
explained first, without adding the unnecessary complications of true, but
potentially confusing facts, to the more complex goal I perceive to be the
questioner's goal. Once the basic concepts sinks in AND the student is
ready for the next level, usually by a response, I then proceed to build.
It
is the old "speak to your audience" concept.
I don't dispute that your explanations are correct. They appear very
good, rather complete. I do believe however, that your most assuredly
honest and well meaning attempt to be correct, completely correct,
actually
makes the subject more confusing to the beginner. I believe this because
I
have been there. In fact, I must, almost every class session, throttle
myself from doing just the very same thing. Why? Because when I do, I
have
succeeded in causing more confusion, resulting in a mental block to
learning
which requires much more effort at damage control to erase the mental
blockage I created with my ignorant desire to be completely correct.
Please
understand that I am being harsh on *myself* because I have been
frustrated
by this and work hard to keep it under control. As an Engineer, teaching
technician students, one must keep in mind that there is a different state
of mind and ability to absorb what to them, appears a very complex
subject...but to my arrogant mind is really very simple. After all,
piecewise parametric polynomial interpolation looked like an impossible
concept, way beyond my comprehension back in 92 when I first saw reference
to it. Now, it looks like the simplest thing any high school Algebra
student can understand.

I'm also at a point in my life that I have seen and done so much
in
this field (and it all seems so simple) that I wish to return some of it
to
others, and I wish to do it very effectively.

Of course, now you're going to tell me that you also have been teaching
for
x years and your methods are equally successful...so be it. There needs
to
me more of us.

BTW...what is your line, Richard?

Some comments, corrections and whatever stuck my fancy about what you
wrote...


"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.

The concept I was trying to relate in a slightly 'light' manner was:
The stuff that happens, happens 'cuz of what we call "physics",
"physical laws" or "nature" or sump-in' like that, not because there is an
equation making it happen. Resistors don't know Ohm's law and don't
conduct
current because of Ohm or his discoveries.

The equation we call Ohm's law is simply a model of how reality works.
Like a model airplane, which helps us understand what a real airplane
looks
like. Ohms law, and all the other equations, help us understand what real
electronics "looks like".


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

A completely valid way to word it, but to a beginner I think the
phrase
"locked in step " is vague. It would be a good start, but probably needs
expansion to explain what it means.



The item called a resistor is the type of resistance that converts
electrical energy to heat energy.
Not all resistances are resistors.

I wouldn't have worded it that way, but it (resistor is the type
of
resistance) is a valid model to have in mind. That is, as a way to
distinguish it from "a resistance which is not a resistor". This made me
think of how I think of it.. and when I use the word "resistance" I think
of
it as as a resistor, yet an impedance has a real or "resistive" part.
That
word "resistance" for me conotes a "resistor" where the others conote the
other concept. Interesting nomenclature, that's all.

Some resistances don`t convert
electrical energy directly into heat. In these non-dissipative
resistances,

Well, here's where I'll say that I think this is truly a matter of
symantics. Your terminlolgy implies that dissipation = heat. I agree
that
the most common usage it that "... is dissipated as heat...". However,
this
next bit:
...is in-phase with current through the
resistance, but it does not cause energy loss.

I think has a symantics problem. I'm sure you truly understand what
happens, but the words "...does not cause energy loss." isn't correct,
because the energy IS lost from the circuit. The circuit "can't tell" the
difference 'tween the resistor and any other kind of resistive component.
It just may or may not be as heat, right?
You know what happens and I know what happens, but the OP didn't,
so
I was starting him down a path that wouldn't paint him into a corner of
not
being able to understand the other resistive types of things later...if so
desired.


An example of lossless
resistance is the Zo or surge impedance of a transmission line.

Again, the power IS lost from the source, no? I think this an
important
basic understanding. To the sourse, it is gone. Poof! never to be seen
again. I think it is a good model to understand and helps go further
without Maxwell complicating things. I think you can go pretty far
without
Maxwell (gee, twice in one paragraph) and still have a good amount of
(correct) sixth sense about what is going on in electronics and
transmission
lines.


Zo is ... yet converts no energy to heat in the lossless line.

And my model didn't exclude this. I thought I was explicit about
that without bringing in more complexity for the OP.


"radiation resistance". ...is hardly a loss.

Again, as far as the transmitter circuitry is concerned, it is.


The following is a well done explanation which goes further and
into
more detail...with one disagreement.

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.

No. In the context of my writing for someone who has an unserstanding
of DC and resistance, reactance it a very confusing factor. It corrupts
an
otherwise simple world. Getting into Vector Algebra and phasors is a
significant step up in mathematics for the beginner not inclined to go the
Engineering route. What I'm saying is that although the unified field
theory may very well be the absolutely correct explanation of everything
in
the universe, we don't need to explain it fully in the beginning to help
someone understand Gravity's acceleration, F=MA and you can't push a rope.
Newton certainly didn't need it. For all I know, F=MA may very well be a
special case in quantum mechanics, but I don't need it to calculate
accelerations, velocities, etc


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

teve Nosko wrote:
"BTW--what is your line, Richard?"

I apologize for a critical tone in my response to Steve`s posting. An
ancient previous discussion of dissipationless resistance in this
newsgroup leaves me primed to comment when it appears unappreciated.

Dissipationless resistance is the stuff which allows a Class C amplifier
exceed 50% efficiency.

I won`t say I`ve been teaching X years, as I`ve never had that role.
Long ago, I found my patience and temperament unsuited to tutoring. I am
a long retired electrical engineer and find entertainment in the
newsgroups.

Best regards, Richard Harrison, KB5WZI

What allows a class-C amplifier to exceed 50% efficiency is a small
operating angle.

Reg, G4FGQ

Reg, G4FGQ wrote:
"What allows a class-C amplifier to exceed 50% efficiency is a small
operating angle."

Exactly, and during the majority of the degrees it`s switched completely
off. It draws no current and suffers no "IsquaredR loss" during the
amplifier off-time. Impedance is approximately E/I, but I is the average
I, which is much less than the bursts of I during the conduction angle.

The switched-off time makes the I in the denominator of E/I very small
indeed and the solution to Ohm`s law is a high impedance without the
dissipation of a resistance that remains in place continuously while
agitating the atoms of a poor conductor to limit current.

Instead, we have a low-resistanc in high conducton for short spurts.
On-time is limited, instead of conduction, to produce a certain
effective resistance.

An automobile Kettering ignition system may use a dwell-meter to
indicate how much of the time the points are closed. An ohmmeter
indicates the resistance between its test prods. The two test circuits
are almost the same although limitation of the deflection of the
dwell-meter is different from limitation of the deflection of the
ohmmeter due to the difference between limited conduction angle ignition
points, and the continuous conduction through a current-limiting
resistor. There`s an analogy between Class C and Class A amplifiers in
there somewhere.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote in message
...
Reg, G4FGQ wrote:
"What allows a class-C amplifier to exceed 50% efficiency is a small
operating angle."

While this is too vague, Richard tries to add detail, but mis-steps just
a bit... and Steve goes into an extended "You ain't quite correct blurb..."


Exactly, and during the majority of the degrees it`s switched completely
off. It draws no current and suffers no "IsquaredR loss" during the
amplifier off-time. Impedance is approximately E/I, but I is the average
I, which is much less than the bursts of I during the conduction angle.

We must be careful with the word "average" here.

First, my "class C" model is a follows:
I liken it to digital or "switched modes". While I have never scoped the
plate to observe this... When the tube is cut off for a large part of the
cycle, there is a high voltage on the tube (I believe it swings higher than
the supply dou to the "ringing" of the plate tuned circuit), but no current.
Hence, ExI=0.
When the tube is on, it is slammed hard on by the "high" grid signal and
there is a high plate current, but the plate voltage is very low (anybody
know how low and if I am all wet? ... tubes aren't quite like transistors
in the digital mode)--therefore ExI=somthing, but since the E is low, it is
lower than in class A during that part of a cycle. There may also be some
effect due to the fact that the plate tank is swinging low allowing the
plate voltage to be even lower.

Did you know that in class A, the plate power dissipated goes DOWN by
the amount that is delivered to the load??? Cool! huh? Isn't physics neat!

Second, it is the RMS current through the tube which will waste power,
so it is what we must be concerned with. Yes, if the tube is off the
current is zero at that time, but the RMS must be considered and it does not
go down as fast you might think. As an example, for the same current
pulses, but spaced out to half the duty cycle, the average drops to half,
but the RMS only drops to .707. There is a square root in there.

[[Anybody see the "AC Watt meter article in QST]] It is an OOPS! Most
power supplies don't draw sine wave current. It is pulses. I have been in
contact with both Bob Shrader (the author) and Stu Cohen (Tech editor) and I
just finished an analysis and am going to make more measurements to verify,
but the numbers Bob published can be as much as 1/3 the true power values
(depending upon the DVM he used and the current waveform of the supplies he
measured.

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

wa-da ya blokes think.



The switched-off time makes the I in the denominator of E/I very small
indeed and the solution to Ohm`s law is a high impedance without the
dissipation of a resistance that remains in place continuously while
agitating the atoms of a poor conductor to limit current.

Instead, we have a low-resistanc in high conducton for short spurts.
On-time is limited, instead of conduction, to produce a certain
effective resistance.

Another way of saying just wjat I did above, but "effective resistance"
is one way of thinking about it and this resistance must be calculated using
the RMS values.

An automobile Kettering ignition system may use a dwell-meter to
indicate how much of the time the points are closed. An ohmmeter
indicates the resistance between its test prods.

I'd be willing to place a bet (knowing how an analog ohm meter works,
that the *diflection* of the two meter pointers is the same (see below).
Both meters respond to the averacge current through them and both will show
full scale when the points are open (I think thta is the correct polarity).
Here's the "below":
There is, however, the confusion added by the coil/cap waveform for which
the ohm meter is not equiped to limit - whereas, I believe the dwell meter,
if well designed, will have something to limit so as to remofe it as a
complicatin.

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

The two test circuits
are almost the same although limitation of the deflection of the
dwell-meter is different from limitation of the deflection of the
ohmmeter due to the difference between limited conduction angle ignition
points, and the continuous conduction through a current-limiting
resistor. There`s an analogy between Class C and Class A amplifiers in
there somewhere.

Best regards, Richard Harrison, KB5WZI

Steve Nosko wrote:
"First, my "class C" model is as follows: I liken it to digital or
"switched modes"."

I do too.

"----Second, it is the RMS current through the tube which will waste
power, so that is what we must be concerned with."

I don`t believe current through a Class C amplifier consists of an
ordinary sine wave. I think it consists of short unidirectional pulses.
The tuned "tank circuit" is the source of sine waves.

RMS is the effective value, not the average value, of an a-c ampere. It
is defined as 0.707X the peak value of the waveform. It is derived from
the average of the squared current over a half cycle, as the heating
value of an ampere is proportional to the current squared.

Speaking inversely, the ratio of maximum to effective value for a sine
wave is 1.414, which is the square root of 2.

Ordinarily, with nonsinusoidal currents, the ratio of maximum to
effective value is not the square root of 2.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
I don`t believe current through a Class C amplifier consists of an
ordinary sine wave. I think it consists of short unidirectional pulses.
The tuned "tank circuit" is the source of sine waves.

Yep, the Class C amp is like the energy pulse from a pendulum
clock spring. The tank/filter circuitry is like the pendulum.
--
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!
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Hi Richard...

"Richard Harrison" wrote in message
...
[...]
"----Second, it is the RMS current through the tube which will waste
power, so that is what we must be concerned with."

I don`t believe current through a Class C amplifier consists of an
ordinary sine wave.

And I didn't say that it does nor do I believe it does. I'm inclined to
take my 100MHz storage scope to to the 6146's of my TS830s and see for
myself.
Your words imply (at least I infer) you are thinking that only a sine
wave has an RMS value. Every wave of any shape has an effective or RMS
value - its heating or "power causing" value.


[...] I think it consists of short unidirectional pulses.
The tuned "tank circuit" is the source of sine waves.

This certainly has to be correct. The tank will most likely cause some
sine-like VOLTAGE waveform, but the tube current has to be pulses of some
shape. This is a very timely discussion in view of the AC power meter QST
article and the extensive investigation I just completed on several pulse
shapes..


RMS is the effective value, not the average value, of an a-c ampere.

I will differ here. The RMS value is more appropriately described as
the power producing value of ANY wave form. Pulses can produce heat just as
well as sine wave AC. We all know this from a practical view since tubes
can only conduct in one direction and the plates DO get hot.



...as the heating
value of an ampere is proportional to the current squared.

This is actually a simplification. P=ExI Power is the product of
voltage and current *only*. Because this is a second order effect, in a
resistance it can be related to either voltage squared or current squared...
because that captures the second order character. Maybe there's a better way
to say it mathematically, but I don't know it.
When we get to non sine shapes, then we have to fall back on the actual
definition. root [avg of square] ...with the integral and all.
http://www.ultracad.com/rms.pdf

[...snip...]

Ordinarily, with nonsinusoidal currents, the ratio of maximum to
effective value is not the square root of 2.
Best regards, Richard Harrison, KB5WZI

Doing the math for pulses with the shape of sine, triangle (a single
slope with sudden end) and trapezoid (a sudden start to one level then a
slope to a peak and a sudden end), I decided to look at the RMS to AVERAGE
ratio since average is what a common meter will measure in Bob Shrader's
article (AC watt meter Jan 04 QST).
I was particularly interested in the sine-shaped pulses of various duty
cycle because the current of common power supplies occurs in short pulses
with a sine-like shape that are near the peak of the voltage waveform.
It was interesting that for all these shapes, this ratio was very
similar. One relatively simple thing to understand which came out of the
analysis was that the average value is directly proportional to the duty
cycle as you might reasonably postulate. Where duty cycle is the ratio of
"on" time to off time. Where "on" time is the time that ANY current flows.
Whereas the RMS is proportional to the Square root of the duty cycle. e.g.
drop the duty cycle to half and the RMS drops to .707.

I have to do some verification, but it sure looks as though Bob's
numbers can be as much as three times what he quoted, depending on the
waveshape and some measurements I made.

http://www.irf.com/technical-info/an949/append.htm
Trapezoid=rectangular. Also for the phase controlled sine, the things that
look like tau and a small n are both pi i.e. sin [pi x (1-D)] cos [pi x
(1-D)] and denominator of 2 x pi


Some average & RMS values here.
http://home.san.rr.com/nessengr/techdata/rms/rms.html

More (better) average formulas:
http://www.st.com/stonline/books/pdf/docs/3715.pdf
NOW I know where the average value of a sine wave comes from = (2/pi)
The Greek delta = d.

A calculator for RMS:
http://www.geocities.com/CapeCanaveral/Lab/9643/rms.htm

"Richard Harrison" wrote in message
...
teve Nosko wrote:
"BTW--what is your line, Richard?"

I apologize for a critical tone in my response to Steve`s posting. An
ancient previous discussion of dissipationless resistance in this
newsgroup leaves me primed to comment when it appears unappreciated.

I only found it mildly critical. Your tone was not interpreted as
hostile in any way, just driven to add.

Dissipationless resistance is the stuff which allows a Class C amplifier
exceed 50% efficiency.

See comment on this later...

I won`t say I`ve been teaching X years, as I`ve never had that role.
Long ago, I found my patience and temperament unsuited to tutoring. I am
a long retired electrical engineer and find entertainment in the

Ahhh! I say, with an air of new found understanding.


newsgroups.

Best regards, Richard Harrison, KB5WZI