Circular polarization... does it have to be synchronous??
 

Jerry:

[snip]
A spinning dipole would require more power to spin it if it had DC on it
than if it had no DC on it. And, actually, it would require no power to
keep the dipole spinning since there would be that theoritical vacuum
around it. But, once you apply the DC, power would be required to keep
it spinning. That amount of added power would be determined by the
amount of DC applied. Do you confirm that this is true?
My question relates to my ignorance about what there is in the "vacuum"
to cause "drag".

Jerry KD6...
[snip]

Roy has got you guys hung up on DC!!!

What is all the magic in DC. DC is just one of a double infinity of
frequency values that
could be applied to a spinning antenna!

This direction of investigation is similar to Cecil Moore's assertion that
there are no
reflections at DC.

There is nothing special about DC, it's just another of the infinity of
excitation
frequencies available.

Hey! Maxwell's/Heaviside's equations do not restrict excitations to any
specific
frequency.

There is no special status assigned to f = 0.0, get over it!

How about f = 0.0000003333 Hz, instead of DC, what then?

-- Pete K1PO

Circular polarization... does it have to be synchronous??
 

Peter O. Brackett wrote:
Jerry:

[snip]
A spinning dipole would require more power to spin it if it had DC on
it than if it had no DC on it. And, actually, it would require no
power to keep the dipole spinning since there would be that
theoritical vacuum around it. But, once you apply the DC, power
would be required to keep it spinning. That amount of added power
would be determined by the amount of DC applied. Do you confirm that
this is true?
My question relates to my ignorance about what there is in the
"vacuum" to cause "drag".

Jerry KD6...
[snip]

Roy has got you guys hung up on DC!!!

What is all the magic in DC. DC is just one of a double infinity of
frequency values that
could be applied to a spinning antenna!

This direction of investigation is similar to Cecil Moore's assertion
that there are no
reflections at DC.

There is nothing special about DC, it's just another of the infinity of
excitation
frequencies available.

Hey! Maxwell's/Heaviside's equations do not restrict excitations to any
specific
frequency.

There is no special status assigned to f = 0.0, get over it!

How about f = 0.0000003333 Hz, instead of DC, what then?

-- Pete K1PO


DC is just AC with a very low frequency. After all you have to turn it
on some time and some day it will turn off.


John Passaneau W3JXP

Circular polarization... does it have to be synchronous??
 

I thought i had myself convinced that it would work, but then talked myself
out of it... and went back to the books.

In my opinion, no, rotating a plane wave, even at the same frequency that it
is oscillating would not create circular polarization. It would create a
rotating plane wave, but it lacks half of the field components to be
circular. The key is in this quote from ramo whinnery and van duzer's
'fields and waves in communications electronics': "if there is a combination
of TWO uniform plane waves of the same frequency, but of different phases,
magnitudes, and orientations of the field vectors, the resultant combination
is said to be an elliptically polarized wave" (emphasis mine). This is of
course the generalized case of the circular one that would require them to
be of the same amplitude and 90 degrees out of phase as they note a few
paragraphs later.

The key is the 'TWO' that I emphasized. If you trace the E field of a
single rotating dipole that is rotating at the same frequency as the rf
driving it you would still see the E field oscillate in amplitude at the
original frequency. So as it propagated, even though the direction of the E
field would follow a circular path the amplitude of it would change at the
same rate, so there would be nulls in the E field every 1/2 cycle... in a
true circular polarized wave the E field is a constant magnitude, it just
rotates around the axis at the given frequency. you can't get that from a
single dipole no matter how you rotate it since there will always be two
zero crossings every cycle in the E and H fields.

i quickly scanned a bunch of the mail, i'm a bit behind in my reading so
please forgive me if someone already came to this conclusion and i missed
it.

Oh, and i briefly saw something about DC fields... actually i 'think' that
if you put a 'dc' charge on a dipole, lets just separate two charges by some
distance and start them rotating about a common center... that MAY actually
create a circularly polarized wave. but i would consider this a degenerate
case of the general problem. Even if you used an ELF rf signal to drive the
dipole you would get zero fields every 1/2 wave which wouldn't work... with
the pure dc charge you have a constant E field that is rotating, and 2
accelerated charges to make the corresponding H field. I think this works
because there are 'TWO' rotating charges that each contribute to the
resulting wave.

Circular polarization... does it have to be synchronous??
 

John:

[snip]
DC is just AC with a very low frequency. After all you have to turn it
on some time and some day it will turn off.


John Passaneau W3JXP
[snip]

I agree, DC is nothing special... DC is 'just' another frequency!

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

Circular polarization... does it have to be synchronous??
 

Dave:

[snip]
"Dave" wrote in message
...
I thought i had myself convinced that it would work, but then talked myself
out of it... and went back to the books.

In my opinion, no, rotating a plane wave, even at the same frequency that
it is oscillating would not create circular polarization. It would create
a rotating plane wave, but it lacks half of the field components to be
circular. The key is in this quote from ramo whinnery and van duzer's
'fields and waves in communications electronics': "if there is a
combination of TWO uniform plane waves of the same frequency, but of
different phases, magnitudes, and orientations of the field vectors, the
resultant combination is said to be an elliptically polarized wave"
(emphasis mine). This is of course the generalized case of the circular
one that would require them to be of the same amplitude and 90 degrees out
of phase as they note a few paragraphs later.
[snip]

Yes! We all know that nothing is really "rotating" in circular
polarization,
rather circular polarization is merely the presence of two separate linearly
polarized waves that are differ in time phase by 90 degrees and mutually
oriented at 90 degrees (space angle) to each other.

A circularly polarized wave excites a linearly polarized antenna equally
well when oriented at any arbitrary angle. In fact a fundamental
"experimental" test to determine if a wave is circularly polarized is to
receive it (measure it) with a linearly polarized 'test' antenna while
the test antenna is rotated. If the signal strength received on the linear
test antenna is the same at all angles of orientation then the received
wave is circular.

Of course, the useful 'discrimination' property of circularly polarized
waves is most evident when they are used with circularly polarized
antennas not linearly polarized antennas. A circularly polarized
wave of a given chirality, will be received at full strength on a
circularly polarized antenna with the same chirality and will be
rejected (null signal) on a circularly polarized antenna of the
opposite chirality. This property provides the most useful
applictions of circular polarization.

[snip]
The key is the 'TWO' that I emphasized.
[snip]

Yes!

If you trace the E field of a single rotating dipole that is rotating at
the same frequency as the rf driving it you would still see the E field
oscillate in amplitude at the original frequency.
[snip]

Yes, if by 'trace' you mean measure with a linearly polarized antenna.

And you would see exactly the same with "trace' with a circularly
polarized signal.

In other words, there is no difference between the wave generated
by a circularly polarized antenna and a wave generated by a linear
antenna mechanically rotated at the signal frequency.

In each case if you placed a linear receiving antenna in the passing
wave front, and hooked and oscilloscope up to the linear receiving
antenna terminals you would observe exactly the same received signals.

[snip]
and you would observe the same w So as it propagated, even though the
direction of the E field would follow a circular path the amplitude of it
would change at the same rate, so there would be nulls in the E field
every 1/2 cycle...
[snip]

Yes!

[snip]
in a true circular polarized wave the E field is a constant magnitude,
[snip]

NO! Unless you are referring to say the root mean square magnitude of
the E field, the actual instantaneous magnitude of the E vector oscillates.
The E field of any electromagnetic wave is never constant
it is constantly oscillating in a plane transverse to the wave direction
at the RF 'carrier' frequency.

[snip] it just
rotates around the axis at the given frequency.
[snip]

Yes indeed! In the case of circular polarization, there are actually two
separate phase locked linearly polarized (vector) E fields oscillating at
the same frequency but in simultaneous time phase quadrature and space
phase quadrature.

And, here is the important point...

The 'vector sum' of these two orthogonal waves adds up to give an E
vector that appears to be rotating.

Remember that any vector can be resolved into or synthesized from
the sum of other vectors. For example in two-space any vector
can be resolved into two other perpencicular vectors.

(x, y) = (a, b) + (c, d)

Now (a, b) and (c, d) may be linear, but if they are of the form
a = A cos(wt), b = B sin(wt), c = C cos(wt), d = D sin(wt) their
sum (x, y) will appear to be rotating.

Think of the 'projections' of the spoke of a rotating bicycle wheel!

[snip]
you can't get that from a single dipole no matter how you rotate it
[snip]

Yes you can, see above.

[snip]
Oh, and i briefly saw something about DC fields... actually i 'think' that
if you put a 'dc' charge on a dipole, lets just separate two charges by
some distance and start them rotating about a common center... that MAY
actually create a circularly polarized wave.
[snip]

Yes it should, but that's not the particular/specific application or
scenario
that I was originally proposing.

[snip]
but i would consider this a degenerate case of the general problem.
[snip]

Agreed!

My original point was that there is essentially no difference between the
wave
emitted by a conventional circularly polarized antenna (say axial mode
helix [W8JK], or a turnstyle) and a linear antenna spinning mechanically or
spinning
by electronic scanning means, with angular velocity equal to the carrier
frequency.

My claim is that here simply is no way to determine
the difference by any physical measurement. The emitted fields are exactly
the same.

We know that there are good applications for 'conventional' circular
polarization where the rate of field 'rotation' is synchronous with the
carrier frequency.

I was just wondering if there are any good applications for circular
polarization when the rate of field rotation is not synchronous
with the carrier frequency, and if so, how well one could
discriminate between such waves rotating at different angular
velocities.

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

Circular polarization... does it have to be synchronous??
 

"Peter O. Brackett" wrote in message
m...
Dave:

[snip]
"Dave" wrote in message
...
I thought i had myself convinced that it would work, but then talked
myself out of it... and went back to the books.

In my opinion, no, rotating a plane wave, even at the same frequency that
it is oscillating would not create circular polarization. It would
create a rotating plane wave, but it lacks half of the field components
to be circular. The key is in this quote from ramo whinnery and van
duzer's 'fields and waves in communications electronics': "if there is a
combination of TWO uniform plane waves of the same frequency, but of
different phases, magnitudes, and orientations of the field vectors, the
resultant combination is said to be an elliptically polarized wave"
(emphasis mine). This is of course the generalized case of the circular
one that would require them to be of the same amplitude and 90 degrees
out of phase as they note a few paragraphs later.
[snip]

Yes! We all know that nothing is really "rotating" in circular
polarization,
rather circular polarization is merely the presence of two separate
linearly
polarized waves that are differ in time phase by 90 degrees and mutually
oriented at 90 degrees (space angle) to each other.

A circularly polarized wave excites a linearly polarized antenna equally
well when oriented at any arbitrary angle. In fact a fundamental
"experimental" test to determine if a wave is circularly polarized is to
receive it (measure it) with a linearly polarized 'test' antenna while
the test antenna is rotated. If the signal strength received on the
linear
test antenna is the same at all angles of orientation then the received
wave is circular.

Of course, the useful 'discrimination' property of circularly polarized
waves is most evident when they are used with circularly polarized
antennas not linearly polarized antennas. A circularly polarized
wave of a given chirality, will be received at full strength on a
circularly polarized antenna with the same chirality and will be
rejected (null signal) on a circularly polarized antenna of the
opposite chirality. This property provides the most useful
applictions of circular polarization.

[snip]
The key is the 'TWO' that I emphasized.
[snip]

Yes!

If you trace the E field of a single rotating dipole that is rotating at
the same frequency as the rf driving it you would still see the E field
oscillate in amplitude at the original frequency.
[snip]

Yes, if by 'trace' you mean measure with a linearly polarized antenna.

And you would see exactly the same with "trace' with a circularly
polarized signal.

no you wouldn't. with the rotating dipole the E field would have zero
crossings every 1/2 wave even as the direction rotates. with a real
circularly polarized wave the E field is a constant magnitude and just
changes direction. if you break down the wave into 2 orthogonal linearly
polarized waves the zero crossings in one line up with the peaks in the
other so the resultant vector magnitude of the E field is a constant... only
the direction changes.


In other words, there is no difference between the wave generated
by a circularly polarized antenna and a wave generated by a linear
antenna mechanically rotated at the signal frequency.

yes there is, you are missing 1/2 the wave components.


In each case if you placed a linear receiving antenna in the passing
wave front, and hooked and oscilloscope up to the linear receiving
antenna terminals you would observe exactly the same received signals.

Only at multiples of 1/2 wave distances from the transmitting antenna. When
the transmitted peak E field is oriented properly for the receive antenna
you would get a max receive signal. But when you orient the tx antenna so
the max in the tx E field is perpendicular to the rx antenna you get a null.
This pattern repeats every 1/2 wave... again, a real circular signal would
have the 2nd wave component at right angles to fill in those nulls.


[snip]
and you would observe the same w So as it propagated, even though the
direction of the E field would follow a circular path the amplitude of it
would change at the same rate, so there would be nulls in the E field
every 1/2 cycle...
[snip]

Yes!

Ah, so you agree here, but not above... this is the key to the difference.
there are zero crossings of the E field in the rotating plane wave, but NOT
in the circular wave... hence rotating plane waves have nulls every 1/2
wave.



[snip]
in a true circular polarized wave the E field is a constant magnitude,
[snip]

NO! Unless you are referring to say the root mean square magnitude of
the E field, the actual instantaneous magnitude of the E vector
oscillates.
The E field of any electromagnetic wave is never constant
it is constantly oscillating in a plane transverse to the wave direction
at the RF 'carrier' frequency.

no, the E field is a constant magnitude in a true circularly polarized wave,
only the direction changes.


[snip] it just
rotates around the axis at the given frequency.
[snip]

Yes indeed! In the case of circular polarization, there are actually two
separate phase locked linearly polarized (vector) E fields oscillating at
the same frequency but in simultaneous time phase quadrature and space
phase quadrature.

right, there are TWO orthogonal waves... with a rotating dipole you only
have ONE wave whose polarization changes over time. put a circularly
polarized wave through a polarizing filter and you still get a signal no
matter what the orientation. put a polarizing filter in front of your
rotating plane wave and you get a signal that depends on your distance from
the antenna.


And, here is the important point...

The 'vector sum' of these two orthogonal waves adds up to give an E
vector that appears to be rotating.

Right! But go back to the books and look at that vector sum in detail. the
magnitude of it is a constant, only the direction changes. in a rotating
plane wave both the direction and magnitude change because there is no 2nd
field component to fill in the zero crossings.


Remember that any vector can be resolved into or synthesized from
the sum of other vectors. For example in two-space any vector
can be resolved into two other perpencicular vectors.

(x, y) = (a, b) + (c, d)

Now (a, b) and (c, d) may be linear, but if they are of the form
a = A cos(wt), b = B sin(wt), c = C cos(wt), d = D sin(wt) their
sum (x, y) will appear to be rotating.

Think of the 'projections' of the spoke of a rotating bicycle wheel!

RIGHT! so take your rotating dipole and look at it from even multiples of
1/4 wave away... lets assume that the max E field from the tx antenna is
when it is horizontal, and min when it is vertical.... remember, the antenna
rotates 90 degrees as the tx rf also goes from peak to zero crossing... so
the zero crossing will always be when the antenna is vertical and the max
will always be when the antenna is horizontal. So, at even multiples of 1/4
wave you see the max E field in the same orientation as when it was
transmitted, horizontal. Move another 1/4 wave away, so now you are at an
odd multiple of 1/4 wave. now that max E field is vertical and the minimum
is horizontal so your horizontal rx antenna sees the minimum field. Without
that 2nd wave at right angles you have a null in the pattern, the 2nd wave
from a real circular wave would fill in that null and you would have a
constant signal amplitude.


[snip]
you can't get that from a single dipole no matter how you rotate it
[snip]

Yes you can, see above.

No you can't, and you agreed with that statement above, you just didn't know
you did.


[snip]
Oh, and i briefly saw something about DC fields... actually i 'think'
that if you put a 'dc' charge on a dipole, lets just separate two charges
by some distance and start them rotating about a common center... that
MAY actually create a circularly polarized wave.
[snip]

Yes it should, but that's not the particular/specific application or
scenario
that I was originally proposing.

[snip]
but i would consider this a degenerate case of the general problem.
[snip]

Agreed!

My original point was that there is essentially no difference between the
wave
emitted by a conventional circularly polarized antenna (say axial mode
helix [W8JK], or a turnstyle) and a linear antenna spinning mechanically
or spinning
by electronic scanning means, with angular velocity equal to the carrier
frequency.

My claim is that here simply is no way to determine
the difference by any physical measurement. The emitted fields are
exactly
the same.

yes there is. a polarizing filter or just by moving a linear rx antenna
will tell you which is which.


We know that there are good applications for 'conventional' circular
polarization where the rate of field 'rotation' is synchronous with the
carrier frequency.

I was just wondering if there are any good applications for circular
polarization when the rate of field rotation is not synchronous
with the carrier frequency, and if so, how well one could
discriminate between such waves rotating at different angular
velocities.

maybe it could be used for some kind of distance determination by rotating
at a slightly different frequency than the carrier frequency. that would
create a null when measured from a linear rx antenna that moved along the
line of sight at the difference in frequencies. it may be hard to calibrate
and measure since the tx polarization vs time would have to be known so you
could calculate how much rotation there has been at your location... and it
would of course fall apart if it wasn't line of sight and there were any
reflections.


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

Circular polarization... does it have to be synchronous??
 

"Dave" wrote in message
...

"Peter O. Brackett" wrote in message
m...
Dave:

[snip]
"Dave" wrote in message
...
I thought i had myself convinced that it would work, but then talked
myself out of it... and went back to the books.

In my opinion, no, rotating a plane wave, even at the same frequency
that it is oscillating would not create circular polarization. It would
create a rotating plane wave, but it lacks half of the field components
to be circular. The key is in this quote from ramo whinnery and van
duzer's 'fields and waves in communications electronics': "if there is a
combination of TWO uniform plane waves of the same frequency, but of
different phases, magnitudes, and orientations of the field vectors, the
resultant combination is said to be an elliptically polarized wave"
(emphasis mine). This is of course the generalized case of the circular
one that would require them to be of the same amplitude and 90 degrees
out of phase as they note a few paragraphs later.
[snip]

Yes! We all know that nothing is really "rotating" in circular
polarization,
rather circular polarization is merely the presence of two separate
linearly
polarized waves that are differ in time phase by 90 degrees and mutually
oriented at 90 degrees (space angle) to each other.

A circularly polarized wave excites a linearly polarized antenna equally
well when oriented at any arbitrary angle. In fact a fundamental
"experimental" test to determine if a wave is circularly polarized is to
receive it (measure it) with a linearly polarized 'test' antenna while
the test antenna is rotated. If the signal strength received on the
linear
test antenna is the same at all angles of orientation then the received
wave is circular.

Of course, the useful 'discrimination' property of circularly polarized
waves is most evident when they are used with circularly polarized
antennas not linearly polarized antennas. A circularly polarized
wave of a given chirality, will be received at full strength on a
circularly polarized antenna with the same chirality and will be
rejected (null signal) on a circularly polarized antenna of the
opposite chirality. This property provides the most useful
applictions of circular polarization.

[snip]
The key is the 'TWO' that I emphasized.
[snip]

Yes!

If you trace the E field of a single rotating dipole that is rotating at
the same frequency as the rf driving it you would still see the E field
oscillate in amplitude at the original frequency.
[snip]

Yes, if by 'trace' you mean measure with a linearly polarized antenna.

And you would see exactly the same with "trace' with a circularly
polarized signal.

no you wouldn't. with the rotating dipole the E field would have zero
crossings every 1/2 wave even as the direction rotates. with a real
circularly polarized wave the E field is a constant magnitude and just
changes direction. if you break down the wave into 2 orthogonal linearly
polarized waves the zero crossings in one line up with the peaks in the
other so the resultant vector magnitude of the E field is a constant...
only the direction changes.


In other words, there is no difference between the wave generated
by a circularly polarized antenna and a wave generated by a linear
antenna mechanically rotated at the signal frequency.

yes there is, you are missing 1/2 the wave components.


In each case if you placed a linear receiving antenna in the passing
wave front, and hooked and oscilloscope up to the linear receiving
antenna terminals you would observe exactly the same received signals.

Only at multiples of 1/2 wave distances from the transmitting antenna.
When the transmitted peak E field is oriented properly for the receive
antenna you would get a max receive signal. But when you orient the tx
antenna so the max in the tx E field is perpendicular to the rx antenna
you get a null. This pattern repeats every 1/2 wave... again, a real
circular signal would have the 2nd wave component at right angles to fill
in those nulls.


[snip]
and you would observe the same w So as it propagated, even though the
direction of the E field would follow a circular path the amplitude of
it would change at the same rate, so there would be nulls in the E field
every 1/2 cycle...
[snip]

Yes!

Ah, so you agree here, but not above... this is the key to the difference.
there are zero crossings of the E field in the rotating plane wave, but
NOT in the circular wave... hence rotating plane waves have nulls every
1/2 wave.



[snip]
in a true circular polarized wave the E field is a constant magnitude,
[snip]

NO! Unless you are referring to say the root mean square magnitude of
the E field, the actual instantaneous magnitude of the E vector
oscillates.
The E field of any electromagnetic wave is never constant
it is constantly oscillating in a plane transverse to the wave direction
at the RF 'carrier' frequency.

no, the E field is a constant magnitude in a true circularly polarized
wave, only the direction changes.


[snip] it just
rotates around the axis at the given frequency.
[snip]

Yes indeed! In the case of circular polarization, there are actually two
separate phase locked linearly polarized (vector) E fields oscillating at
the same frequency but in simultaneous time phase quadrature and space
phase quadrature.

right, there are TWO orthogonal waves... with a rotating dipole you only
have ONE wave whose polarization changes over time. put a circularly
polarized wave through a polarizing filter and you still get a signal no
matter what the orientation. put a polarizing filter in front of your
rotating plane wave and you get a signal that depends on your distance
from the antenna.


And, here is the important point...

The 'vector sum' of these two orthogonal waves adds up to give an E
vector that appears to be rotating.

Right! But go back to the books and look at that vector sum in detail.
the magnitude of it is a constant, only the direction changes. in a
rotating plane wave both the direction and magnitude change because there
is no 2nd field component to fill in the zero crossings.


Remember that any vector can be resolved into or synthesized from
the sum of other vectors. For example in two-space any vector
can be resolved into two other perpencicular vectors.

(x, y) = (a, b) + (c, d)

Now (a, b) and (c, d) may be linear, but if they are of the form
a = A cos(wt), b = B sin(wt), c = C cos(wt), d = D sin(wt) their
sum (x, y) will appear to be rotating.

Think of the 'projections' of the spoke of a rotating bicycle wheel!

RIGHT! so take your rotating dipole and look at it from even multiples of
1/4 wave away... lets assume that the max E field from the tx antenna is
when it is horizontal, and min when it is vertical.... remember, the
antenna rotates 90 degrees as the tx rf also goes from peak to zero
crossing... so the zero crossing will always be when the antenna is
vertical and the max will always be when the antenna is horizontal. So,
at even multiples of 1/4 wave you see the max E field in the same
orientation as when it was transmitted, horizontal. Move another 1/4 wave
away, so now you are at an odd multiple of 1/4 wave. now that max E field
is vertical and the minimum is horizontal so your horizontal rx antenna
sees the minimum field. Without that 2nd wave at right angles you have a
null in the pattern, the 2nd wave from a real circular wave would fill in
that null and you would have a constant signal amplitude.


[snip]
you can't get that from a single dipole no matter how you rotate it
[snip]

Yes you can, see above.

No you can't, and you agreed with that statement above, you just didn't
know you did.


[snip]
Oh, and i briefly saw something about DC fields... actually i 'think'
that if you put a 'dc' charge on a dipole, lets just separate two
charges by some distance and start them rotating about a common
center... that MAY actually create a circularly polarized wave.
[snip]

Yes it should, but that's not the particular/specific application or
scenario
that I was originally proposing.

[snip]
but i would consider this a degenerate case of the general problem.
[snip]

Agreed!

My original point was that there is essentially no difference between the
wave
emitted by a conventional circularly polarized antenna (say axial mode
helix [W8JK], or a turnstyle) and a linear antenna spinning mechanically
or spinning
by electronic scanning means, with angular velocity equal to the carrier
frequency.

My claim is that here simply is no way to determine
the difference by any physical measurement. The emitted fields are
exactly
the same.

yes there is. a polarizing filter or just by moving a linear rx antenna
will tell you which is which.


We know that there are good applications for 'conventional' circular
polarization where the rate of field 'rotation' is synchronous with the
carrier frequency.

I was just wondering if there are any good applications for circular
polarization when the rate of field rotation is not synchronous
with the carrier frequency, and if so, how well one could
discriminate between such waves rotating at different angular
velocities.

maybe it could be used for some kind of distance determination by rotating
at a slightly different frequency than the carrier frequency. that would
create a null when measured from a linear rx antenna that moved along the
line of sight at the difference in frequencies. it may be hard to
calibrate and measure since the tx polarization vs time would have to be
known so you could calculate how much rotation there has been at your
location... and it would of course fall apart if it wasn't line of sight
and there were any reflections.


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

Hi Pete

I dont think a rotating dipole with DC on it will generats a field that
propogates. Your post reads as though you dont think the rotating DC
dipole will producing a propogating Far Field. I read other posts that
seem to indicate that others assume the DC spinning dipole will generate a
propogating "far field". It is sad that I am so lazy that I cannot express
myself using Cross Products. But, I submit that it takes more than rotating
a dipole to produce a propogating far field.

I dont understand where the "Cross H" is generated by a rotating DC
dipole, as required for propogation.

I dont understand why it requires more power to rotate a DC dipole with
increased voltage on it, as required to account for the increased power.

Jerry KD6JDJ

Circular polarization... does it have to be synchronous??
 

Jerry:

[snip]
I dont think a rotating dipole with DC on it will generats a field that
propogates. Your post reads as though you dont think the rotating DC
dipole will producing a propogating Far Field. I read other posts that
seem to indicate that others assume the DC spinning dipole will generate a
propogating "far field". It is sad that I am so lazy that I cannot express
myself using Cross Products. But, I submit that it takes more than
rotating a dipole to produce a propogating far field.

I dont understand where the "Cross H" is generated by a rotating DC
dipole, as required for propogation.

I dont understand why it requires more power to rotate a DC dipole with
increased voltage on it, as required to account for the increased power.

Jerry KD6JDJ
[snip]

What is required to generate electromagnetic radiation is any movement of
electric charge such that there exists a rate of change of the positional
acceleration
of electric charge. This can be derived from first principles from the
Maxwell/Heaviside
equations. There is a section in the volume of Feynman's Lectures on
Physics that
discusses this, and I believe that the previous editor of QEX magazine wrote
an
article outlining a derivation of this a year or so ago.

In physics and dynamics the rate of change of acceleration is termed "jerk".

In terms of simple differential calculus, there is position ("x"), there is
velocity
("v = dx/dt") the rate of change of position, there is acceleration ("a =
dv/dt")
the rate of change of velocity, and there is jerk ("j = da/dt") the rate of
change of acceleration. Expressing it in these terms, it can be said that
it
it can be shown from the Maxwell/Heaviside partial differential equations
that govern all of electromagnetics, that radiation occurs when ever
electric
charge is "jerked". i.e. whenever the rate of acceleration of charges
changes
either up or down.

Now in sinusoidal realms, where all the signals are assumed to be of sine
wave shapes, we know from simple differential calculus that differentiating
sine waves results in more sine waves. In other words a sine wave current
comprises electric charges changing position according to a sine waveform,
and so perforce is the velocity, acceleration and jerk of those charges.
Hence
whenever electric current motion follows a sine-like wave there will be
radiation caused by the sinusoidal 'jerk'.

Now there are more forms of acceleration than just sine wave motion.

For example when things have angular motion, there is centrifugal
acceleration, and when things move on a rotating frame there
is coriolis acceleration, etc... and so in general whenever electric
charges are put in motion, the exception being simple motions where
the third derivative of motion is zero, there will be radiation caused
by that motion.

All of the above details are well known to most physicists who study
electromagnetics, from first principles (Maxwell/Heaviside), these 'facts'
are less well known to most (modern) electrical Engineers.

Consequently I find it easy to believe that the mechanical motion of
any body with electric charge on it, be that charge DC or AC is highly
likely to radiate electromagnetic waves.

All of this is difficult, actually impossible, to simulate with NEC codes
like Roy's EZNEC since those analysis codes all assume a simple
steady state fixed sinusoidal regime for the framework in which
the Maxwell/Heaviside equations are solved. NEC does not
provide for the simulation of antennas in motion! And so...

It is beyond the capability of NEC in general or EZNEC in
particular to generate field patterns for rotating dipoles!

Othewise someone (Cecil maybe?) would already have run
a simultation on EZNEC to refute my claims to being able
to generate circular polarization by mechanical rotation.

In other posts in these threads on CP I have asked if anyone
knows of any simulation software (generally would be in the
category called "multi-physics packages" that can adequately
simulate/calculate the fields for rapidly rotating dipoles driven
by sinewaves at arbitrary frequencies. If so I'd like to know.
And I'd like to simulate some of my "theories" just to prove
my assertions.

Actually it may be easier to emulate (i.e. prototype) such
a spinning dipole. In fact one does not have to mechanically
spin a dipole to do this. One can generate the same fields
as a spinning dipole by applying the "right" signals to two
orthogonal linear dipoles. i.e. a synthetic or phased array
beam former, that emits circularly polarized beams of
arbitrary rotation velocity.

Phased arrays can be elctronically scanned or rotated,
this is in fact how most modern STAP radars work, e.g.
Aegis, etc... and so one can electronically rotate emitted
waves in the same way. It's not cheap, but it can be done.

My curiosity is along the lines of if you could find a cheap
way of rapidly spinning an emitting dipole, what new
applications might arise from that.

As far as I can determine, no one has yet done the experiments
that I have been discussing here in these threads.

And so my suggestions/theories are met with comments
like, "It's never been done before, why would you want to do it,
etc, etc... ?

Why do I ask such questions?

Just curious or perhaps I'm just plain stupid!

But no one has yet been able to categorically refute my assertion.

Whenever charge is jerked there is radiation!

Food for thought.

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

Circular polarization... does it have to be synchronous??
 

On Fri, 12 Dec 2008 11:46:47 -0500, "Peter O. Brackett"
wrote:

What is required to generate electromagnetic radiation is any movement of
electric charge such that there exists a rate of change of the positional
acceleration
of electric charge.

What a lot of bafflegab. For one sentence movement is named,
described, AND inferred three times; and charge tied to two of them.

Peter, when the ladies say NO to you, they probably have to have it
annotated, indexed, and footnoted before you get it.

73's
Richard Clark, KB7QHC

Circular polarization... does it have to be synchronous??
 

Richard:

[snip]
"Richard Clark" wrote in message
...
On Fri, 12 Dec 2008 11:46:47 -0500, "Peter O. Brackett"
wrote:
..
..
..
Peter, when the ladies say NO to you, they probably have to have it
annotated, indexed, and footnoted before you get it.

73's
Richard Clark, KB7QHC
[snip]

Richard, hey, clearly you have never met me in person. In person I am even
more persuasive than in my often
ill prepared USENET postings, it has been my experience that the ladies
NEVER SAY NO to me!

Heh, heh...

I was an only son, raised in a large family of sisters by my mother who was
often alone since my father was a seagoing
sailor. And so... at a very early age I learned to "convince" the ladies of
the veracity of my assertions and requests.

Long since grown into a man, I'll turn 67 next week, I have polished my
approach to the point that the ladies always
accept everything I say. Heh, heh... Whenever I ask the ladies a question
or state an assertion in my own inimitiable way their
responses are always along the lines of...

"I'll bet you say that to all the ladies" and they invariably end with,
"sure you may, it would be my pleasure, you are such a smooth talker".
[grin]

Smooth talker, sweet talker, what ever works, I say!

On that particular subject there was a "cute" but interesting, entertaining
and amusing two page piece in last month's Esquire magazine
entitled something like, "The Smooth Talker" or "How to be a Smooth Talker".
It was really quite an amusing piece, and apropos to
the current thread.

If you don't get Esquire take the time to look up that piece at your local
library, I'm sure that you will get a laugh or two, I did.

OK, enough of this 'aside', let's get back to the real technical discussion
at hand.

None of the guru's lurking around this particular newsgroup (r.r.a.a) will
deny that whenever electrical charge is "jerked" that photons are emitted.
And... none of the gurus hanging hereabouts will deny that photons can have
'spin'.

The only question remaining is that of the relative quantities of left and
right hand 'spin' of photons in any specific situation where
photons have been 'jerked' lose from the electrical charge and whether the
'spin' is quantized or continuous.

Comments, thoughts?

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

PS: Gosh, I've missed this group.... Cecil is fine, but it's just not been
the same since dear Reggie passed. I miss Reg, especially at this time
of year. At least one could easily understand the King's English as written
by dear Reg, and Cecil's English is not that bad for an "Aggie", but
Richard, since your purple prose takes English expression to a completely
different level, you certainly help keep this group entertained. Thanks
for what you do for us all!