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Circular polarization... does it have to be synchronous??
John:
[snip] I think investing some time with this math (it's not all that difficult) [snip] Agreed! [snip] will provide one with insight into the concept of polarization and perhaps head off some misconception. If anyone is interested and has Mathcad, I've got a worksheet that allows one to vary these parameters, plots the resulting ellipse (or circle or line) and also calculates ellipticity (axial ratio) and eccentricity. Sincerely, and 73s from N4GGO, John Wood (Code 5550) e-mail: Naval Research Laboratory 4555 Overlook Avenue, SW Washington, DC 20375-5337 [snip] Thanks John! -- Pete K1PO |
Circular polarization... does it have to be synchronous??
Dave:
[snip] "Dave" wrote in message ... J. B. Wood wrote: I think investing some time with this math (it's not all that difficult) will provide one with insight into the concept of polarization and perhaps head off some misconception. If anyone is interested and has Mathcad, I've got a worksheet that allows one to vary these parameters, plots the resulting ellipse (or circle or line) and also calculates ellipticity (axial ratio) and eccentricity. Sincerely, and 73s from N4GGO, All I have to know is that Circular Polarization always helps when one end of the path is prone to random polarizations, even with the 3 dB power loss. [snip] Yep, CP is good! No matter how it is generated... -- Pete K1PO |
Circular polarization... does it have to be synchronous??
[snip]
A patch antenna, circularly polarized, mounted at the end of a motor shaft, rotating in the opposite direction of the polarization... .... at a speed equal to the frequency... Does the polarization "unravel" and emit a linear, non-rotating polarization ? [snip] Ype that's exactly what would happen! [snip] Is this the sort of principle that you were trying to convey ?? [snip] Yeah, you've got it man! [snip] If this is the case, any discrepancy in the motor, say 1 hz out of 10 Mhz , would result in an Efield rotating at a 1 hz rate.... and the receiving antenna would have to be very very very long in order to fully receive the polarized wave....... I think.... And if the motor shaft and the frequency were identical, the Efield would be linear, stable, and non-rotating..... [snip] I can see that you did not find that so hard to "grok". Good work man! Thanks! [snip] This is getting beyond my personal antenna expertise, but I still find it interesting....... Please pardon my lack of understanding, .... if I [snip] Andy! No problem you have it... there is no lack on your part. Fortunately you do not seem to be encumbered by convention. Your understanding is "right on"! -- Pete K1PO |
Circular polarization... does it have to be synchronous??
Roy:
[snip] "Roy Lewallen" wrote in message treetonline... Something just occurred to me. I did get to thinking. My previous answers were wrong. [snip] Yep, I thought as much... [snip] Peter's spinning antenna wouldn't produce a circularly polarized wave (as universally defined) even if it was synchronous with the wave frequency. As I've said, a circularly polarized wave has constant E field amplitude; Peter's wave would have a time-varying amplitude. If it were synchronous, the nulls and peaks would always occur at the same places in the rotation cycle, so they would occur at fixed angles relative to a rotational reference point. If non-synchronous, the nulls and peaks would rotate at the beat frequency. [snip] The problem is... that most "conventional" code and theory, e.g. NEC does not allow for antennas in motion. These theories and computer codes/algorithms are based upon a static steady state solution of the Maxwell/Heaviside equations... i.e. E is a "fixed" phasor rather than an oscilating waveform. [snip] It seems to me that the way to mechanically generate a circularly polarized wave would be to rotate a source of *static* E field, for example, a short dipole with constant applied DC voltage at the feedpoint. [snip] Hmmm... restricting that dipole to a "static" source is really far too restrictive. This assumption likely results from the assumption that E is a sinusoidal steady state value rather than a dynamic (transient) wave. [snip] That should produce a circularly polarized wave with the frequency being the rotational frequency of the dipole. At any point in space, the E field would change with time, and would propagate, and it would look exactly like a circularly polarized wave broadside to the rotation plane. [snip] Yes, but E is not "fixed" in time, it is the magnitude of an oscillating phasor! A DC phasor would not propagate. Of course! [snip] If the scheme works and radiation is occurring, then power must be going into the antenna, which in turn means it's drawing current that's in phase with the applied voltage. When stopped, no current will flow, but when rotating, it does. So how does the antenna know it's rotating? How about this -- if you instantaneously move the antenna into some position, a static E field appears there, and propagates outward at the speed of light. Closer in than the leading edge of the propagating wave, the field is static. When we rotate the dipole to a new position, it moves through the field from its previous position, which induces a current in it. Hence the current. It's fundamentally a generator, with the field being in the air. [snip] Yes that would be the case if the rotating antenna was excited with DC, however that is not necessarily the general case. In general the "center" frequency or "carrier" frequency may be any arbitrary frequency, down to and including DC. Maxwell's/Heaviside's equations hold for all frequencies from zero (DC) to infinity. [snip] I'd be willing to bet a moderate sum that if you did apply a DC voltage to a dipole and rotated it, you'd see an alternating current with a frequency equal to the frequency of rotation, and a circularly polarized wave broadside to the antenna. [snip] Wow! Roy.... you are taking a big risk here. What is the (exact) value of that "sum"? [snip] I suspect that the current and the radiated field increase in amplitude with rotational speed, so you might have to get it going really fast before you can detect the effects. Now there's some food for thought. Roy Lewallen, W7EL [snip] Agreed! Hey... not many are able to "think outside the envelope", but I do believe we are getting to the edge... -- Pete K1PO |
Circular polarization... does it have to be synchronous??
[snip]
"christofire" wrote in message ... .. .. .. A source of endless coffee-time debates where I used to work! No, the current into the rotating dipole would be DC and the means of rotation at the radio frequency would take the place of the 'transmitter'. If the current were alternating then the radiated electric field would be discontinuous but it isn't; it has constant magnitude. Between two such systems separated by many wavelengths, if there were no anisotropic material around, reciprocity would apply and a means of conveying DC by radio would be created! [snip] Perhaps, but.... the intersting case is when the "center" frequency is somewhat higher than DC. [snip] However, intriguing and amusing as this analogy might be I wonder if it really has any practical value. [snip] T. J. Watson, the early CEO of IBM is reputed to have stated, "I see no real requirement for more than 7-10 computers in this world!" [snip] For real mechanical rotating parts the frequency would be limited to something rather low like the tens of kHz at which Alexanderson alternators work, and then the wavelength would be so long that it would probably be impossible to construct an efficient radiator*. The quickest moving antenna I've encountered was a commutated plasma antenna, using a construction similar to a 'dekatron' tube, but even then the length of the radiator was so small that SHF would be needed to achieve worthwhile radiation efficiency* and the maximum commutation speed was limited to a few MHz by the time it takes to establish the plasma at each step in the commutation cycle. [snip] What if you could electronically rotate antennas at any desried (practically) high frequency? Consider, for example phased arrays driven through elecronically controlled phase shift networks. Would that work? [snip] *(Of course, the conventional principles of radiation resistance vs. loss resistance may need 'massaging' to bring them into line with the concept of creating transverse waves by rotating a dipole connected to a battery!) [snip] Rotating dipoles do not have to (only) be connected to batteries. They could be connected to signal generators operating at 3.765MHz, no? -- Pete K1PO |
Circular polarization... does it have to be synchronous??
[snip]
Hi Chris I am not smart enough to analyze the effects of rotating a dipole with DC applied to it, but I have doubts that it would create a "far field". Did you guys ever figure out how the "DC dipole" generates a Far Field? Jerry KD6JDJ [snip] Jerry... no one on this thread, except perhaps Roy, has restricted the "frequency" of the signal applied to said mechanically rotating dipole to be zero, f = 0!! In fact, in principle, the frequency of the signal applied to the rotating dipole could be any desired frequency selected from the frequency range minus infiinty to plus infinity. -- Pete K1PO |
Circular polarization... does it have to be synchronous??
Roy:
[snip] "Roy Lewallen" wrote in message ... Jerry wrote: .. .. .. The whole thing is just a mental exercise to help gain a better understanding of the nature of a circularly polarized field. Roy Lewallen, W7EL [snip] I agree that it is an exercise to help gain a better understanding of circular polarization, but... It is not just a "mental" exercise. I believe that hhere are practical applications of this phenomena! FWIW.... -- Pete K1PO |
Circular polarization... does it have to be synchronous??
Jerry:
[snip] I will respectfully submit that a car alternator doesnt so much spin a magmetic field as it Rotates the field past a conductor. A car alternator is a lumpy magnetic field that is spun past stationary coils of wire. There is no misunderstanding about inductive coupling of close by conductors. My question related to far field "radiation". I am aware that my understanding of far Field radiation is very limited, so i dont propose that i have answers. I do have question about generating a far field by spinning a DC excited dipole. Jerry KD6JDJ [snip] There are many practical examples extant of such "rotating" fields... Consider the rotating field generated within the stator of a "shaded pole" electric motor, or perhaps the roing field of a synchronous electric motor. However the rotating electromagntic fields of AC electric motors have conventionally been synchronized with the frequency (60Hz in North America) of the exciting waveform. That commercial application does not preclude applications wherein the rotating field of an AC motor is not synchronous with the exciting prime mover. For example, imagine a motor wherein the stator magnets are rotated by a separate mechanical device, bicycle pedals?, that pulls the rotor around at a frequency not synchronized with the stator prime mover excitation. Just because there is no real commerciall application for such a motor in today's markets, does not mean that such is not useful for some other purpose. Open minds create new applications -- Pete K1PO |
Circular polarization... does it have to be synchronous??
Jerry:
[snip] Tell me, did you guys ever decide that there would be a far field generated by the spinning dipole with DC on it? I dont refer to the inductive field. Maybe there is no way to separate Far Field from any condition where an inductive field is generated. Jerry KD6JDJ [snip] If the answer for DC was no, then.... What is your answer for a spinning dipole with 0.0001Hz on it, or say 1, 000, 003.33333 Hz on it? Food for thought? -- Pete K1PO |
Circular polarization... does it have to be synchronous??
Jerry:
[snip] "Jerry" wrote in message ... .. .. .. Yeah, I never ascribed any practical use to the "CP by spinning". But, there are some fundamentally good thoughts generated here. For instance, I can easily see why two dipoles rotating at the same rate and rotational direction will couple *nothing*. Thats like trying to receive RHCP with a LHCP antenna. I have lived a long time without understanding Poynting and Maxwell (almost 100 years older than me), I wouldnt want to change that now. Jerry KD6JDJ [snip] Hey, the shareholders in the pony express company never ascribed any practical use to the internal combustion engine... -- Pete K1PO |
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! |
Circular polarization... does it have to be synchronous??
Peter O. Brackett wrote:
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 Do you have any hobbies? |
Circular polarization... does it have to be synchronous??
Dave:
[snip] Do you have any hobbies? [snip] Technical hobbies, or social hobbies? Other than kibitzing on r.r.a.a? Would you believe that I'm a salsa dancing champion? Actually my wife Kathy (who is a dance genius) and I do a lot of dancing which might be described as a "hobby" of sorts. Let me tell you about one of our recent dance escapades. About three weeks ago my wife and I were in Paris, France, returning from three weeks in Italy where, among other things, we hiked to the top of Vesuvius. But that's another story! All this to say that we stopped over for a night in Paris on our way back to Indialantic from Naples. We took the opportunity to take in dinner and a show at the celebrated Moulin Rouge near Pigalle in Paris. Ouch! That was an expensive evening! It didn't look too bad in Euros, but when the bill showed up on my Visa statement in US$ it was heart stopping! Front row seats at the Moulin Rouge, right up against that venerable125 year old stage, and the multi-course meal with a magnum of champagne was great and as you will note from the rest of my "story" it turned out to be a memorable evening! Kathy and I took the train from CDG airport into the Gare du Nord, and then we took the Paris Metro over to the Pigalle station leaving time to get lost at least three times before we got there. Pigalle as you know is in the center of the "red light district" of Paris. The Moulin Rouge is in the middle of that district on Monmatre, the dandy's, Princes and Princesses do not walk along Pigalle to get to the Moulin Rouge like Kathy and I did, rather they arrive right in front of the door in long black Mercedes limousines. Well... at the Moulin Rouge they serve a first class dinner before the show if you elect to take the dinner and show rather than just the show. During dinner, a small elegant music ensemble is fronted by a talented duet of singers, who are sort of the Parisian equivalent of Edye Gorme and Steve Lawrence, except they sing in French, such songs as "Chanson d'Amour", etc. as enteratinment for the diners. During dinner that part of the main stage that later becomes elevated during the main show is kept at ground level so that people can dance if they wish, during dinner, and before the main show. The Moulin Rouge was packed the night we were there and, as usual whenever there are lots of "observers", there were not many dancers on the floor! Only a couple of pairs, who had consumed all of their champagne by that time got up to dance staggered through a few 'slow dance' steps, and so the floor of the Moulin Rouge looked downright barren. My wife Kathy suggested that WE get up and dance. As a dance instructor, you can well imagine that Kathy is not shy about that kind of thing. My athy always likes to be the first one out on the dance floor. Well the small ensemble and the two singers got round to a number with a certain beat (NC2S) that my wife and I like and so Kathy suggested that we get up on the Moulin Rouge dance floor in front of the whole audience that night and do the Night Club Two Step. Now for those of you who don't know, the NC2S is a modern dance that was "invented" by and American, Buddy Schwimmer of Costa Mesa, CA a few years ago. NC2S is a very elegant dance done to slower music and is very elegant and quite unique. Aside: NC2S is known in the USA but likely not well known in Europe. In case you are not a dancer, you should know that Buddy Schwimmer happens to be the father of Benji Schwimmer who won the "So You Think You Can Dance" show two years ago, and he is also the father of Lacey Schwimmer who was partnered with Lance Bass on the "Dancing with the Stars" show this past fall. Lacey and Lance came in second on the show this year, after that graceful "Brooke Burke" and her partner Derek Hough. And so... "there we were", my wife Kathy and I dancing the elegant Night Club Two Step all alone on the dance floor of the Moulin Rouge in Paris, in front of an International audience of several hundred people. Well... we were surprised! As we danced together to that beautiful slow and sexy music, all of the dinner "chatter" stopped and all eyes in that famous 125 year old theatre, were on us as I showcased Kathy's wonderful dance skills (as the dance partner/leader). The highlight came as the music ended and we walked back to our dinner table. The audience at the Moulin Rouge favored us with a standing ovation! Apparently they had never seen the Night Club Two Step before! Unfortunately no one recorded the happenings at the Moulin Rouge that night, but... for those of you who might be interested to see what the NC2S looks like as it is danced, you see an example on You Tube, just click on... http://www.youtube.com/watch?v=VoyxrEbZpSw BTW... the Moulin Rouge show after dinner and dancing was spectacular and well worth the $$$$$. I suppose that if it were not a 125 year old tradition in Paris that the Moulin Rouge show mighty be described by Americans as a "high end" Las Vegas show, except that... Las Vegas, NV was not even in existence when the Moulin Rouge started its run 125 years ago! I'd say that one should really describe Las Vegas shows as pale imitations of the Moulin Rouge show! [smile] Guys who are reading this will be pleased to know that not only is the whole show spectacular, but the show girls at Moulin Rouge are spectacular as well. All this to say, Dave.... yes I do have hobbies! And... I am often "asked to dance"... BTW.... I highly recommed dance to any man/boy who wants to be closely asociated with women! Dave, I'd challenge you to name a hobby for a man that is as exciting as a hobby where the man gets to hold attractive girls in his arms and run his hands all over thier bodies for 3-5 minutes at a time and the girls thank him when it's over and asks him if they could do it again soon? Ciao! -- Pete K1PO -- Indialantic By-the-Sea, FL |
Circular polarization... does it have to be synchronous??
On Sat, 13 Dec 2008 09:41:46 -0500, "Peter O. Brackett"
wrote: 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. At the risk of being so identified with that villified group, I will deny that statement (for what it is worth). And... none of the gurus hanging hereabouts will deny that photons can have 'spin'. That is a fairly short list of what is "not" denied. Why don't you go further like Gurus refuse to deny: 1. They hate their parents; 2. They stopped beating their wives; 3. The earth is perfectly round; 4. Gussian arrays are the perfect metaphor for radiation; .... n. and on and on and -heh heh- on. 73's Richard Clark, KB7QHC |
Circular polarization... does it have to be synchronous??
Richard:
[snip] "Richard Clark" wrote in message ... On Sat, 13 Dec 2008 09:41:46 -0500, "Peter O. Brackett" wrote: 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. At the risk of being so identified with that villified group, I will deny that statement (for what it is worth). [snip] Your denial is not worth to much simply because, as The Bard had one of his thespian protagonists quote, "methinks he doth protest too much". And, so... well, I am afraid to admit that... I don't really know which of the honored denziens of this group (r.r.a.a) are the select members of the secret clique of lurkers known as "The Gurus". It seems from what you have written above that you deny being one of The Gurus. I believe it was Groucho Marx who said, "I wouldn't want to be a member of any club that would accept me as a member", and so... Me? Hmmm... I not only deny membership in The Gurus, but I actually know that I am not a member. Now, if my recollection is correct, Reg Edwards may have known the names on that secretive list of gurus, but since Reg has now passed to his reward and, although we have evidence of Reg's own electromagnetic expertise in the form of the many programs and web site information he graciously left for us gratis, there is no evidence that Reg ever belonged to The Gurus. In fact, I recall Reg indirectly denying his own membership on many occasions by referring difficult and sometimes rhetorical questions to "The Gurus", often answering those questions himself after much newsgroup discussion. Apparently Art Unwin has definite knowledge of who The Gurus are, since he often challenges and castigates them at the same time. Unfortunately Art would condemn the poor IEEE because of corrupt behavior, and so I am not sure that Art is really connected in the electromagnetic world. All this musing to note that... USENET is a great tool for scientific discussion, that adheres to the most basic tennets of "The Scientific Method". Why, anyone... from freely identified persons, to anonymous posters, may make whatever assertions and pose whatever theories they care to, and everyone knows that eventually the truth will be revealed as those assertions are examined in the brilliant light of the scientific cross examination that occurs in these r.r.a.a threads! Hey! Where's Art when you need him? Art... I've created your opening, now its your turn... It's saturday night and I gotta go dancing, the girls are waiting... :-) -- Pete K1PO -- Indialantic By-the-Sea, FL care to and |
Circular polarization... does it have to be synchronous??
On Sat, 13 Dec 2008 18:21:10 -0500, "Peter O. Brackett"
wrote: 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. At the risk of being so identified with that villified group, I will deny that statement (for what it is worth). Your denial is not worth to much simply because, as The Bard had one of his thespian protagonists quote, "methinks he doth protest too much". I didn't think the question had any legs either. D.O.A. Apparently Art Unwin has definite knowledge of who The Gurus are, since he often challenges and castigates them at the same time. He is like Septimus who awaits the death of his six brothers before ascending to the crown. Art... I've created your opening, now its your turn... Stand back then, because you'll find him spitting at you in the chance of catching me in the backwash. 73's Richard Clark, KB7QHC |
Circular polarization... does it have to be synchronous??
On Dec 13, 5:21*pm, "Peter O. Brackett"
wrote: Richard: [snip]"Richard Clark" wrote in message ... On Sat, 13 Dec 2008 09:41:46 -0500, "Peter O. Brackett" wrote: 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. At the risk of being so identified with that villified group, I will deny that statement (for what it is worth). [snip] Your denial is not worth to much simply because, as The Bard had one of *his thespian protagonists quote, "methinks he doth protest too much". And, so... well, I am afraid to admit that... I don't really know which of the honored denziens of this group (r.r.a.a) are the select members of the secret clique of lurkers known as "The Gurus". It seems from what you have written above that you deny being one of The Gurus. I believe it was Groucho Marx who said, "I wouldn't want to be a member of any club that would accept me as a member", and so... Me? Hmmm... I not only deny membership in The Gurus, but I actually know that I am not a member. Now, if my recollection is correct, Reg Edwards may have known the names on that secretive list of gurus, but since Reg has now passed to his reward and, although we have evidence of Reg's own electromagnetic expertise in the form of the many programs and web site information he graciously left for us gratis, there is no evidence that Reg ever belonged to The Gurus. *In fact, I recall Reg indirectly denying his own membership on many occasions by referring difficult and sometimes rhetorical questions to "The Gurus", often answering those questions himself after much newsgroup discussion. Apparently Art Unwin has definite knowledge of who The Gurus are, since he often challenges and castigates them at the same time. *Unfortunately Art would condemn the poor IEEE because of corrupt behavior, and so I am not sure that Art is really connected in the electromagnetic world. All this musing to note that... USENET is a great tool for scientific discussion, that adheres to the most basic tennets of *"The Scientific Method". Why, anyone... from freely identified persons, to anonymous posters, may make whatever assertions and pose whatever theories they care to, and everyone knows that eventually the truth will be revealed as those assertions are examined in the brilliant light of the scientific cross examination that occurs in these r.r.a.a threads! Hey! *Where's Art when you need him? *Art... I've created your opening, now its your turn... It's saturday night and I gotta go dancing, the girls are waiting... :-) -- Pete K1PO -- Indialantic By-the-Sea, FL care to and Peter, there are no gurus on this newsgroup period When I extended the Gaussian law of statics by making it a dynamic field I proved beyond doubt that radiation was via particles and not waves. David and others denied that you could even bring in the subject of statics when discussing radiation even tho it is known that the force between particles is part and parcel of Maxwells laws. I might add that many joined him in this thinking like lemings. Since that time all of this group have sunk lower and lower with respect to radio. All have demanded a definition of equilibrium no less so all are lacking in science. They have all denied that mathematically my extension of Gauss results in the same mathematics that were arrived at by Maxwell. When I point out that eddy current ( really a field) is the weak force that Einstein was looking for as he was convinced that radiation held the clue he was looking for. Yup they howled at that one too. Ofcourse it was Maxwell who found out that one of the existing laws by the masters was not in equilibrium which he then corrected by adding the displacement current which describes the action of the eddy current field in lifting and applying spin to a charged particle. Howls again from all as this could not be found in any books. Ofcourse this operation in a macro scale is used daily in scrap yards for sorting out materials as well as non destructive testing but again the howls rose again. So I then told them that maxwell based computor programs account for all the forces used in radiation which they could find out for themselves with a optimizer program as long as the input was not slanted towards a planar design so that it may be discarded But then they are self perceived gurus thus don't need to use a computer as all is already known, ala their books that are more than 50 years old. I then informed them that one naval base had tipped all their verticles for better performance by incorporating the weak fork which also can be confirmed using Maxwells laws. Now I am being considered and idiot no less. So I then posed the question as to where the current goes when reaching the top of a fractional wave antenna and the answers I got was that a closed circuit is not required for radiation. And this thinking goes on and on but at no time has anybody come forward to refute my analysis in anyway, mathematics, computor programs or what ever. This whole story reminds me of the Yagi invention that was dismissed totally by the Japanese intelligensia but embrace by the rest of the world such that the Japanese never used the Yagi design thru out the length of the war which was their loss. Peter, all of the above has been pointed out to this group of self perceived gurus over the past few years but all has been denied as it is no where in the books to be read. When I joined this group more than a decade ago Roy W7EL said he was going to expose all the old wives tales that floated around including all the newly touted sciences that were being tossed around but his silence has been defining while at the same time Snakespere has been prancing around in his fishnet pants while talking in tongues. Ian is still demon strating how to solder a connector on coax while the Naval instructor Woods in Washington is in total belief that the US navy is using tilted antennas for superior performance. No Peter, there are no gurus on this newsgroup as I have one time or another proved that they are nothing more than talking heads beyond doubt. As an aside Peter on another subject I have no bone to pick with the professional societies only the Universities for giving away information provided by tax payers money and thus was not theirs to remove from publics eyes Best regards Art Unwin.......KB9MZ.......xg (uk) |
Circular polarization... does it have to be synchronous??
Art Unwin wrote:
... I proved beyond doubt that radiation was via particles and not waves. ... Best regards Art Unwin.......KB9MZ.......xg (uk) Actually, that is false ... you could not prove such a thing, unless you force us to disbelieve our own eyes! To proceed claiming such is only to invite us to think you daft! http://www.newscientist.com/article/...1_head_dn14172 The best you can now argue is that light is composed of a type(s) of particle(s) which travels as a wave(s); And, still, it seems to possess both qualities--i.e., behaving both as particles AND waves ... but then, we already knew that. Regards, JS |
Circular polarization... does it have to be synchronous??
On Dec 13, 9:38*pm, John Smith wrote:
Art Unwin wrote: * ... I proved beyond doubt that radiation was via particles and not waves. * ... Best regards Art Unwin.......KB9MZ.......xg (uk) Actually, that is false ... you could not prove such a thing, unless you force us to disbelieve our own eyes! *To proceed claiming such is only to invite us to think you daft! http://www.newscientist.com/article/...ts&nsref=news1.... The best you can now argue is that light is composed of a type(s) of particle(s) which travels as a wave(s); *And, still, it seems to possess both qualities--i.e., behaving both as particles AND waves ... but then, we already knew that. Regards, JS John I am confident about my analysis. Scientists have not been able to explain anything in radio that procedes at the or near the speed of light or explain how communication is resolved. I have provided an explanation that is duplicated in many ways every day and vindicated by Maxwells equations. Reviewing the URL you supplied. The photograph is not a simple proof that it appears to be. Camera pictures are notorious in fooling people into falible interpretatations. However you can believe what you want. I would point out that I have melded many things and aproaches such that all mesh in a single conclusion None of these separate aproaches have had any errors pointed out whether it be mathematics or otherwise. I am not a programmer so there is no way I could have injected such a complicated scenario into all the programs now available. Nor could I have invented the weak force that Einstein was convinced resided in the analysis of radiation. On the other hand there are many photographs available of the Lock Ness monster, alien space craft and alabaster statues with tears coming from the eyes. By the way, compare different aproaches of resolving radiation analysis and check which form provides the minimum losses and you will find that planar antennas just don't measure up versus antennas in equilibrium. On the other hand if the field of an eddy current is not the weak force that Einstein forcast or predicted then where and what is this force that propels a wave, presumably without spin that knocks out what I have suggested? At the same time does it fit exactgly the jigsaw pussle that Maxwell left us with the puzzle turned over so the picture could not be pre determined? And as a finale I see particles occilating possibly in tandem form that gives the impression that the particles arenot interconnected in string form but a series of interactions between particles that operate in their own right als H2O in molecular but unbound form as with mass Best regards...... good effort but no cigar. I would aim for best results at the computer programs or finding the true weak force, or determining how a electrical wave travels with intelligence or the center of all proove that the mathematics as applied to gaussian boundary that is made dynamic under a time varying field DOES NOT equate with the mathematical laws of Maxwell and last of all that the term equilibrium has NO PLACE in the laws devised by the masters with respect to the Universe. I left out the part that a radiater must be straight as expoused by some pseudo experts in the radio field as well as to how the addition that Maxwells made to his laws provide the mathematics for the tilting action on a radiator for minimum lossand the many other things I have pointed out My very best regards and best wishes in any endeavor that you wish to undertake in an effort to proove me in error. There will be some talking in tongues by the group but I am absolutely positive there will be no fresh revalations other than just words provided over the years which have meant nothing other than the intent to hurt. Goodnight Art Unwin KB9MZ..........XG....(UK) |
Circular polarization... does it have to be synchronous??
Art Unwin wrote:
On Dec 13, 9:38 pm, John Smith wrote: Art Unwin wrote: ... I proved beyond doubt that radiation was via particles and not waves. ... Best regards Art Unwin.......KB9MZ.......xg (uk) Actually, that is false ... you could not prove such a thing, unless you force us to disbelieve our own eyes! To proceed claiming such is only to invite us to think you daft! http://www.newscientist.com/article/...ts&nsref=news1... ... Reviewing the URL you supplied. The photograph is not a simple proof that it appears to be. Camera pictures are notorious in fooling people into falible interpretatations. However you can believe what you want. I would point out that I have melded many things and aproaches ... Art Unwin KB9MZ..........XG....(UK) Well, that is simple enough then. You are to have us disbelieve our own eyes ... good enough, we have that cleared up. Regards, JS |
Circular polarization... does it have to be synchronous??
On Dec 14, 3:50*am, John Smith wrote:
Art Unwin wrote: On Dec 13, 9:38 pm, John Smith wrote: Art Unwin wrote: * ... I proved beyond doubt that radiation was via particles and not waves. * ... Best regards Art Unwin.......KB9MZ.......xg (uk) Actually, that is false ... you could not prove such a thing, unless you force us to disbelieve our own eyes! *To proceed claiming such is only to invite us to think you daft! http://www.newscientist.com/article/...ts&nsref=news1... * ... Reviewing the URL you supplied. The photograph is not a simple proof that it appears to be. Camera pictures are notorious in fooling people into falible interpretatations. However you can believe what you want. I would point out that I have melded many things and aproaches ... Art Unwin KB9MZ..........XG....(UK) Well, that is simple enough then. *You are to have us disbelieve our own eyes ... good enough, we have that cleared up. Regards, JS John you can interprete what you want. For me I will await for somebody to prove me wrong in the many areas that I have espoused and allow those that just want to make nasty remarks go ahead with their agenda. Sooner or later reason will prevail and Snakesphere talking in tongues will fade away.. I look forward to the time that a real guru on radiation appears on the group to discuss what is salient to the subject Very best regards Art Unwin.......KB9MZ........xg (uk) |
Circular polarization... does it have to be synchronous??
Art Unwin wrote:
... John you can interprete what you want. For me I will await for somebody to prove me wrong in the many areas that I have espoused and allow those that just want to make nasty remarks go ahead with their agenda. Sooner or later reason will prevail and Snakesphere talking in tongues will fade away.. I look forward to the time that a real guru on radiation appears on the group to discuss what is salient to the subject Very best regards Art Unwin.......KB9MZ........xg (uk) Now, we approach that time of risking way too much verbiage on way too little. Yes, I do trust my eyes. The research done to get that picture was done by a university; I don't believe the lady, who was head, was out to reinforce any preconceived ideas/theories. And, I don't believe New Scientist is a nutter-rag-on-the-fringe; It does push-the-evelope. THAT is my interpretation; I fear it the only one possible, at this time. Light and, most-probably, EM (no picture, yet) behaves with properties BOTH resembling particles and waves. (Thank gawd, at least something gives us valid reason for argument!) You can wait for the cows-to-come-home; that research stands; the picture is NOT a fraud--IMHO. I have no reason to "be nasty"; I simply believe it to be as it appears ... I am at a loss for what Shakespeares' stance would be; As you say, may reason prevail. My very definition of the meaning of "guru" is "clueless" (in the context which I have used the word here); Now, you wish to wait for one of "them?" scratches-head Salient? Change that to logical and I will "look forward" with you ... now, please, don't "be nasty" ... end-of-story. Regards, JS |
Circular polarization... does it have to be synchronous??
Art Unwin wrote:
... Very best regards Art Unwin.......KB9MZ........xg (uk) By-the-way, a sine wave (such as is seemingly depicted in that picture) is nothing less than a circle (360 degrees)--"traveling." I don't believe you were "lost" on that point, but stated here just to make sure ... Regards, JS |
Circular polarization... does it have to be synchronous??
Art Unwin wrote:
... Very best regards Art Unwin.......KB9MZ........xg (uk) By-the-way, a sine wave (such as is seemingly depicted in that picture) is nothing less than a circle (360 degrees)--"traveling." I don't believe you were "lost" on that point, but stated here just to make sure .... or, simply, "a traveling circle." Regards, JS |
Circular polarization... does it have to be synchronous??
On Sun, 14 Dec 2008 09:07:23 -0800, John Smith
wrote: Art Unwin wrote: Sooner or later reason will prevail and Snakesphere talking in tongues will fade away. I am at a loss for what Shakespeares' stance would be; As you say, may reason prevail. Shakespeare will have little to say about it. The term "speaking in tongues" comes from the New Testament: http://www.bible.org/page.php?page_id=393 Also, reason has rarely prevailed. It's usually rationalization, seduction, politix, or main force that carries the argument. None of these show any indication of fading away. How I create circular polarization or simulate a rotating antenna direction finder. Pretend I'm holding an antenna: http://www.LearnByDestroying.com/panorama/jeffl.htm When it's done loading, move the mouse around the picture. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Circular polarization... does it have to be synchronous??
Jeff Liebermann wrote:
... How I create circular polarization or simulate a rotating antenna direction finder. Pretend I'm holding an antenna: http://www.LearnByDestroying.com/panorama/jeffl.htm When it's done loading, move the mouse around the picture. ROFLOL!!! Great! Best laugh I have had on here in quite awhile ... Thanks, warm regards, JS |
Circular polarization... does it have to be synchronous??
On Sun, 14 Dec 2008 08:00:47 -0800 (PST), Art Unwin
wrote: I look forward to the time that a real guru on radiation appears on the group to discuss what is salient to the subject Sorry, but the messiah is busy trying to save the multitudes from, moral debauchery, religious damnation, economic meltdown, global warming, and the evil oil cartels. Antenna design and theory will have to wait until all the other evils are dealt with. Also, guru means "teacher". There are several current and former teachers that post high quality answers here fairly regularly. If all you want is a guru, they're readily available. All you have to do is read, listen, and understand. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Circular polarization... does it have to be synchronous??
Jeff:
How I create circular polarization or simulate a rotating antenna direction finder. Pretend I'm holding an antenna: http://www.LearnByDestroying.com/panorama/jeffl.htm When it's done loading, move the mouse around the picture. Cool! Finally someone with an open mind, good on you... Lurkers will note that... Jeff is circularly polarized! Been a while since I was in Santa Cruz. Been a while since I ran SCO... Thanks Jeff. -- Pete K1PO -- Indialantic By-the-Sea, FL |
Circular polarization... does it have to be synchronous??
On Dec 5, 8:17*pm, "Peter O. Brackett"
wrote: Group: Warning... this could be mind blowing! Conventionally electromagnetic wave 'polarization' refers to the relative physical spatial orientation of the electric field vector (E) of an electromagnetic wave. It is commonly understood that polarization of electromagnetic waves may be either linear or circular. Linear Polarization (LP): Of course waves that are linearly polarized may have any arbitrary orientation angle (theta) with respect to a reference frame such as the earth's surface. *For example most common linear amateur antennas produce and/or respond to waves of linear polarization, and these antennas produce either either horizonally or vertically polarized waves depending upon the orientation of the (linear) antenna with respect to the earth's surface (ground). As examples; a 1/2 wave length dipole for 10 meters hung at 30 feet between two trees of equal height produces a largely horizonally polarized wave and, a 2 meter 1/4 wave dipole mounted in the center of the roof of an automobile produces a largely vertically polarized wave. Of course as electromagnetic waves are propagated throughout an environment are never purely orientated and usually contain an ensemble of many orientations, because the waves are reflected from the ground, trees, buildings, mountains, bridges, moving vehicles, and sometimes propogated through moving and anisotropic media such as the ionosphere, etc... and so the multiple reflection surfaces at various angles to the earth's surface and/or refractions and Faraday rotations will conspire to "mix up" the original orientation of the E vector of a purely linear transmitted wave and usually produces a quite mixed polarization at distance from an emitting antenna. Malus' Law {I = Io [cos(theta)]^^2} describes the response of a linearly polarized receiving antenna to waves arriving at a polarization angle theta relative to the receiving antenna's preferred orientation. *i.e a horizontally polarized antenna will produce maximum response to horizontally polarized waves and a minimum response (zero) to a vertically polarized wave and vice versa. Of course in practice, because of the multipath reflections and refractions the 'cross response' is never exactly zero or maximum as predicted by Malus Law. Just the same it is preferable to have the orientation *of a receiving antenna 'aligned' with that of a particular transmitting antenna. *In the HF region it is difficult for hams to "rotate" the orientation of their receiving antennas to maximize signal pickup based upon polarization, and so most hams are forced to take whatever response their relatively fixed antennas produce to the relatively unknown orientation of received waves. In military or commercial installations, where money and space may not be an issue, either electronically or mechanically derived spatial antenna polarization diversity can be utilized to maximize received signal strength based upon arriving polarization. *Polarization diversity receivers... Circular Polarization (CP): Circular polarization describes the condition when an electromagnetic wave is spinning or rotating with around its direction of transmission. *That is the electric vector (E) of a circularly polarized electromagnetic wave is rotating with an angular velocity as the wave travels through space. *This is in contrast to the E vector of a linearly polarized wave which merely oscillates in one linear direction. Just as with linear polarization (horizontal and vertical) there are two different distinctly possible orientations for circularily polarized waves, these are known as Right Hand Circular Polarization (RHCP) and Left Hand Circular Polarization (LHCP). * There are actually two well known conventions used to label R and L CP depending upon the community of interest, *namely physics/optics and electrical/electronics. *Usually electronics folks refer the direction of rotation to the rotation of the E vector around the direction of travel from a transmitting antenna, whilst the optical physicists refer the rotation of E around the direction of travel towards a receiving lens. *It's the same as the definition of up and down, it's all in the eye of the beholder. *Regardless there are two orientations for CP Apparently circular polarization is less commonly known and understood than linear (horizontal/vertical) polarization especially among hams. There exist RHCP antennas and there are LHCP antennas. Perhaps one of the easiest forms of CP antennas for hams to understand are the axial mode helix antennas first discovered/studied by the great radio astronomer/ham John Kraus W8JK. *Axial mode helix antennas may be "wound" with either a right hand thread or a left hand thread. Again Malus Law applies, in an easily applied modified form and so... RHCP receiving antennas respond to RHCP waves and *LHCP receiving antennas respond to LHCP waves. *A purely RHCP antenna will produce zero response to an LHCP wave, etc... An interesting effect happens upon reflection of CP waves. *An RHCP wave reflected from a perfectly reflecting surface returns (is echoed) as a LHCP wave! CP propagation is often used in Satellite communications where a satellite may use both RHCP and LHCP transmitting antennas on the same frequency for communicating independently with two different ground stations using R and L CP *antennas on the same frequency. *CP frequency diversity doubles channel capacity! Yet another common form of CP antenna uses crossed linear antennas fed with a 90 degree (Pi/2) phase difference excitation. As far as I know all currently known CP antennas such as axial mode helixes and crossed 90 degree linear arrays produce CP waves where the angular velocity of rotation is one revolution per cycle of the RF carrier, or in other words one radian of circular rotation for each radian of frequency transmitted. *In other words most well known CP antennas produce ONLY synchronous CP, where the angular velocity of rotation of the E vector is synchronized exactly with the frequency of the wave being transmitted. I believe that the well known and understood situation of purely synchronous CP is NOT necessesarily the only form of CP. Warning... The following may be an invention! Consider the case of a linear antenna, say a dipole, fed from a feed line over rotating slip rings, such that the antenna can be rotated while it is transmitting. Now transmit on that dipole antenna whilst mechanically spinning it clockwise [RHCP?] (with a mechanical motor of some kind). The dipole antenna is linear and thuse emits linear polariztion, except it is mechanically spinning, and so the E vector emanating from the antenna will be rotating with respect to its direction of travel. In this case the angular velocity of the motor that spins the linear antenna need not be synchronous with the frequency being radiated. For example we *could mechanically spin the antenna at 330 rpm while transmitting a carrier of 1 GHz. This would most certainly produce circular polarization. *For is not the E vector spinning at 330 revs! In fact the astute newsreader may note that we need not use a motor to rotate the antenna. *In fact, I can propose several ways of "electronically" rotating the linear antenna at any arbitrary angular velocity, not necessarily synchronous with the transmitted frequency and so produce a so-called non-synchronous CP at any desired rate of rotation. Clearly, according to Malus Law, the maximum response to the non-synchronous CP received waves from this 'rotating' antenna contraption would be from a similarily rotating receiving antenna! Question? What would be the response of an axial mode helix antenna or say crossed 90 degree fed dipoles or any other "synchronous" CP antenna to such a non-synchronous wave produces by a rotating antenna? Would the response of a syncrhronous axial mode helix be less than that of a sympathetically rotating receiving antenna? What? Thoughts, comments? -- Pete K1PO -- Indialantic By-the-Sea, FL Pete Said, "Circular polarization describes the condition when an electromagnetic wave is spinning or rotating with around its direction of transmission. That is the electric vector (E) of a circularly polarized electromagnetic wave is rotating with an angular velocity as the wave travels through space. This is in contrast to the E vector of a linearly polarized wave which merely oscillates in one linear direction." Pete, I believe this is your error in thinking,instead of a a spinning field perhaps it would be better just to few it as a coil moving towards you with no rotation. Jimmie |
Circular polarization... does it have to be synchronous??
JIMMIE wrote:
oscillates in one linear direction." Pete, I believe this is your error in thinking,instead of a a spinning field perhaps it would be better just to few it as a coil moving towards you with no rotation. Jimmie Two colocated matched antennas 90 degrees apart electrically, one at a right angle to the other, will make very nice CP. |
Circular polarization... does it have to be synchronous??
"Peter O. Brackett" wrote in message m... Jeff: How I create circular polarization or simulate a rotating antenna direction finder. Pretend I'm holding an antenna: http://www.LearnByDestroying.com/panorama/jeffl.htm When it's done loading, move the mouse around the picture. Cool! Finally someone with an open mind, good on you... Lurkers will note that... Jeff is circularly polarized! he may be twisted, but hardly circularly polarized! |
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