Roy Lewallen wrote:
Now if we could just get a certain individual to either stay on the
rotor or the stator and not keep jumping back and forth without telling
anyone or even realizing it himself. . .

I apologize for any confusion I may have created. All of my
phasors are referenced to the feedpoint current at zero
degrees, which is what EZNEC does.

If the feedpoint forward current is at zero degrees, the
forward current 45 degrees away will lag by 45 deg.
The reflected current 45 degrees away will lead by 45 deg.
The forward current 90 degrees away will lag by 90 deg.
The reflected current 90 degrees away will lead by 90 deg.
Thus the forward current and reflected current phasors
are rotating compared to the feedpoint reference.

The standing wave current phase, referenced to the feedpoint
phase, changes hardly at all. The standing wave current
phase is essentially the same all up and down the dipole.
The standing wave current phase is essentially the same at
the bottom and top of a loading coil. The standing wave
current phase is essentially unrelated to the position
on the antenna or loading coil. Standing wave current
cannot be used to determine the phase shift through
a loading coil.
--
73, Cecil http://www.w5dxp.com

Roy Lewallen wrote in
:

with a rotational speed of omega * t radians/sec. The reason the
time-dependent rotational term

Should that be ...of omega radians/sec..., omega*t is the phase
displacement, omega is the phase velocity?

You're right. Thank you for the correction. My apology for the error.

And to correct myself, I really should have said angular displacement and
angular velocity respectively.

Owen

Cecil Moore wrote:

Gene Fuller wrote:

I heard a rumor that the FCC does not like people to inject class-C
type pulses directly into an antenna from the output of an amateur
transmitter.

Perhaps that rumor is just an urban legend, however, and non-linear
outputs are welcome.


The subject is modeling a class-C source, Gene,
not filtering a class-C source. We all know how
to filter a class-C source. Do you have a model
for a class-C source?

Well, we used to have one waaay back in Non-linear Transistor Design.
Done with harmonics and relatively simple math as I remember. Gave
remarkably accurate answers only using the fundamental plus 2 or 3 of
them. The course was mostly about tank circuits, doublers, triplers,
PLLs, etc. though, since the non-linear stuff was so easy once learned.

Of course it wasn't really a model of a class-C source, since it
actually did anything you could think of. So I guess it wouldn't qualify.

Sorry I mentioned the concept.

tom
K0TAR

Keith Dysart wrote in news:1177719266.182305.327520
@l77g2000hsb.googlegroups.com:

On Apr 27, 7:36 pm, K7ITM wrote:
Grrrr. I'll try to
remember to check the couple of books I have that would talk about
phasors to see if I'm misrepresenting them, but I'm pretty sure they
are equally explicit in defining a phasor as a representation of ONLY
the phase and magnitude of the sinusoidal signal, and NOT as a vector
that rotates synchronously with the sinewave.

My recollection is of being introduced to phasors with the study of
electric machines which have real rotating magnetic fields. By
jumping onto the rotor and rotating with those magnetic fields,
solutions became trivial by allowing vector arithmetic on the now
stationary phasors.

Isn't hopping onto the rotor (assuming synchronous speed) to make your
observations called moving from the time domain to the frequency domain,
and all the mathematical shortcuts are only valid if all quantities share
the same angular velocity (or frequency), implying sinusoidal waveform.

I guess a departure from the strict phasor environment is for example
when we consider a noise vector rotating about the end of a carrier
phasor in exploring FM detector S/N vs C/N.

Owen

Tom Ring wrote:
Well, we used to have one waaay back in Non-linear Transistor Design.

Yes, I remember one from college but would have trouble
locating it 50 years later. :-)
--
73, Cecil http://www.w5dxp.com

Owen Duffy wrote:
Isn't hopping onto the rotor (assuming synchronous speed) to make your
observations called moving from the time domain to the frequency domain,
and all the mathematical shortcuts are only valid if all quantities share
the same angular velocity (or frequency), implying sinusoidal waveform.

Ever wonder which direction, clockwise or counter-clockwise,
a standing-wave phasor is rotating?
--
73, Cecil http://www.w5dxp.com

On Apr 27, 4:01 pm, Roy Lewallen wrote:
K7ITM wrote:

OK, noted, but your definition doesn't match what I was taught and
what is in the Wikipedia definition athttp://en.wikipedia.org/wiki/Phasor_(electronics).
What I was taught, and what I see at that URL, is that the PHASOR is
ONLY the representation of phase and amplitude--that is, ONLY the
A*exp(j*phi). To me, what you guys are calling a phasor is just a
rotating vector describing the whole signal. To me, the value of
using a phasor representation is that it takes time out of the
picture. See alsohttp://people.clarkson.edu/~svoboda/eta/phasors/Phasor10.html,
which defines the phasor very clearly as NOT being a function of time
(assuming things are in steady-state). But in my online search, I
also find other sites that, although they don't bother to actually
define the phasor, show it as a rotating vector. Grrrr. I'll try to
remember to check the couple of books I have that would talk about
phasors to see if I'm misrepresenting them, but I'm pretty sure they
are equally explicit in defining a phasor as a representation of ONLY
the phase and magnitude of the sinusoidal signal, and NOT as a vector
that rotates synchronously with the sinewave.

Tom,

I'm sure a lot of people forget the derivation of a phasor after using
it for a while, just as they do so many other things.

Again, a phasor is a complex representation of a real sinusoidal
function and, as such, definitely has a time varying component. That the
component isn't written doesn't mean it's not there. By all means, check
your texts. I'm sure that any decent circuit analysis text has a
serviceable development of the subject.

I always cringe when I see wikipedia quoted as a reference -- I was
referred to an entry regarding transmission lines some time ago, and it
contained some pretty major misconceptions. That leads me to mistrust it
when looking up a topic which I don't have a good grasp of. I don't have
a full understanding of the process by which it's written, but it seems
that all participants in this newsgroup are equally qualified to create
or modify a wikipedia entry. How could that result in a reliable reference?

Roy Lewallen, W7EL


Hi Roy,

Well, I did not forget the derivation. In Balabanian, "Fundamentals
of Circuit Theory," (a book I have but didn't actually study from) he
uses "sinor" instead of "phasor" but says they are the same, then in a
convoluted way gets around to saying that it's just the phase and
magnitude, and not the real(exp(jwt)) part. Smith, "Circuits,
Devices, and Systems," (most likely the book from which I learned
about phasors) is much clearer about it. Under "Phasor
Representation" in my edition,

"If an instantaneous voltage is described by a sinusoidal function of
time such as
v(t) = V cos (wt + theta)
then v(t) can be interpreted as the "real part of" a complex function
or
v(t) = Re {V exp[j*(wt + theta)]} = Re
{[V*exp(j*theta)]*[exp(j*wt)]} (eqn 3-18)
In the second form of eqn 3-18, the complex function in braces is
separated into two parts; the first is a complex constant, the second
is a function of tiem which implies rotation in the complex plane.
The FIRST PART we DEFINE [Tom's emphasis...] as the phasor (bold) V (/
bold), where
(bold) V (/bold) = V*exp(j*theta)
....
The phasor V is called a "transform" of the voltage v(t); it is
obtained by transforming a function fo time into a complex constant
which retains the essential information. ... "

OK, so your definition is different from mine. So far, I've found two
actual definitions of the phasor on-line, and both agree with my books
and my own useage. But if it's common useage to consider a phasor to
be a rotating vector, I'll defer to that at least in this discussion.
So far, though, I haven't found a reason to give up my definition of a
phasor. ;-)

Cheers,
Tom

Owen Duffy wrote:

Isn't hopping onto the rotor (assuming synchronous speed) to make your
observations called moving from the time domain to the frequency domain,
and all the mathematical shortcuts are only valid if all quantities share
the same angular velocity (or frequency), implying sinusoidal waveform.

I guess a departure from the strict phasor environment is for example
when we consider a noise vector rotating about the end of a carrier
phasor in exploring FM detector S/N vs C/N.

That's why it's essential to not forget the implied exp(j * omega * t)
term -- all waveforms in an analysis must include it, and it must be the
same omega for all. In addition to inherently non-sinusoidal waveforms,
waveforms resulting from any nonlinear operation, such as frequency
modulation or multiplying or squaring waveforms, can't be analyzed in
that environment.

Roy Lewallen, W7EL

K7ITM wrote:

OK, so your definition is different from mine. So far, I've found two
actual definitions of the phasor on-line, and both agree with my books
and my own useage. But if it's common useage to consider a phasor to
be a rotating vector, I'll defer to that at least in this discussion.
So far, though, I haven't found a reason to give up my definition of a
phasor. ;-)

Cheers,
Tom

I find it's convenient to think of a phasor as rotating with respect to
some other frequency, or stationary when you want to show the phase
relation at some specific frequency in a circuit with complex impedances.

For example, if you are discussing the phase relations in AM modulation,
you can set the carrier as a vector pointing to the right, and the upper
and lower sidebands rotating in opposite directions with their centers on
the end of the carrier vector.

The sidebands each have one half the amplitude of the carrier, so when they
are aligned in the same direction as the carrier, the resulting vector is
twice the amplitude, or length. When they oppose the carrier, the result is
zero amplitude.

So a phasor can be stationary or rotating depending on its relation to
something else in the discussion.

Regards,

Mike Monett

On Apr 27, 9:15 pm, Owen Duffy wrote:
Keith Dysart wrote in news:1177719266.182305.327520
@l77g2000hsb.googlegroups.com:
My recollection is of being introduced to phasors with the study of
electric machines which have real rotating magnetic fields. By
jumping onto the rotor and rotating with those magnetic fields,
solutions became trivial by allowing vector arithmetic on the now
stationary phasors.

Isn't hopping onto the rotor (assuming synchronous speed) to make your
observations called moving from the time domain to the frequency domain,

I am not sure it is that; more like rotating the frame of reference to
stabilize the view (or a stroboscope perhaps?). The time domain is
now captured in the notation on the diagram that says it is all
happening
at 60 Hz, for example.

and all the mathematical shortcuts are only valid if all quantities share
the same angular velocity (or frequency), implying sinusoidal waveform.

But I agree with this. If everything is not rotating with the same
velocity
(and not just frequency), then it is difficult to find a useful frame
of reference
to rotate.

Which suggests that if there are two directions of rotation, phasors
don't help much with the solution.

I guess a departure from the strict phasor environment is for example
when we consider a noise vector rotating about the end of a carrier
phasor in exploring FM detector S/N vs C/N.

....Keith