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Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
The only kind of electromagnetic waves I know about are the traveling kind. Sorry I can't be more help. Seems to beg the question - are standing-waves electromagnetic waves? If so, why are they standing? If not, what are they? (Rhetorical questions AFAIAC) -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote:
Jim Kelley wrote: Richard Harrison wrote: "Since the velocity with which the signal propagates along the helix wire approximates the velocity of light if the frequency is not too low (caveat is unimportant, see footnote in book), the axial field due to the signal advances with a velocity that is very closely the velocity of light multiplied by the ratio of helix pitch to helix circumference." Fig. 7-19 is certainly interesting. Cecil owes you a fruit basket I think. ;-) Unfortunately, I must disagree (very slightly) with Kraus. Using Kraus' concepts *verbatim*, the delay through a coil would be the same whether the wire is coiled up or straightened out (if I understand correctly what he is saying). On my web page at w5dxp.com/current2.htm I have a 30 turn coil with a diameter of 6" causing a 38 degree phase shift at 3.8 MHz. If the coil were straightened out, it would be about pi*6"*30 = 565 inches or 47 feet. Since a wavelength is about 259 feet at that frequency, 47 feet would be about 65 degrees. So Kraus' rule-of-thumb is off by about 70%. His VF would be about 0.009 where the actual VF is more like 0.106. 65 degrees of wire doesn't replace 65 degrees of antenna. In this case, 65 degrees of wire replaces 38 degrees of antenna. The "missing degrees" are in the impedance discontinuity between the coil and stinger. There is an interaction between turns that increases the VF of the coil so there is a very tiny grain of truth in what Tom says. The interaction between turns increases the coil VF from Kraus' 0.009 to the actual value of 0.016 but certainly not all the way to 1.0 as W8JI asserts. Kraus may have been off by 70% but W8JI is off by 6000% so it seems that Kraus was still a lot closer to the technical truth that W8JI ever was. Cecil, I don't have the third edition of Kraus' antennas book, but I do have the second edition. He does not make that simplified statement in the second edition. He has equations and charts showing how the Vf changes with the dimensions of the coil and the wavelength. He also references a paper by Chu and Jackson that is now about 60 years old. In that paper, the authors show that the Vf increases dramatically as the relative wavelength becomes longer with respect to the coil dimensions. 73, Gene W4SZ |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote:
Jim Kelley wrote: Perhaps it should be noted that electromagnetic waves and photons travel neither faster nor slower than the speed of light in their medium of travel. Obviously true for traveling waves. But how about the "electromagnetic waves and photons" involved in standing waves? Some folk here would have us believe that they are not moving at all. Cecil, So do you actually believe that standing waves are completely static and inert? 73, Gene W4SZ |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
Tom hasn't posted a single word to this thread that I am aware of. The point is if you don't like what he says, you should take it up with him. Know what I mean? What is your agenda in asserting that the contents of Tom's web page concerning loading coils and his past postings on the subject are off limits for this newsgroup? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil, W5DXP wrote:
"But how about the electromagnetic waves and photons involved with standing waves?" Terman has an answer. The standing wave is only a manifestation of interference between two waves traveling in opposite directions, so on page 870 of his 1955 opus Terman writes: "The directional characteristic of a resonant (standing wave) system is the vector sum of the directional patterns pointed in opposite directions, as illustrated in Fig. 23-8." In other words, the wave traveling in one direction produces its pattern and the wave traveling in the other direction produces its pattern. The sum of the patterns in both directions is the directional pattern for the rod or wire. Standing waves have nothing to do with it but to stand there and do nothing. Best regards, Richard Harrison, KB5WZI |
Phase Shift through a 75m Texas Bugcatcher Coil
Gene Fuller wrote:
I don't have the third edition of Kraus' antennas book, but I do have the second edition. He does not make that simplified statement in the second edition. I have the 3rd edition, but I have not been able to find the previous quotations. I certainly hope that I am not disagreeing with Kraus. "Coils" or "Loading Coils" are not even in the index. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Gene Fuller wrote:
So do you actually believe that standing waves are completely static and inert? Of course not, Gene, but some on this newsgroup apparently believe that. (Hint: I said it was a rhetorical question). Why do some posters on this newsgroup go out of their way to deny the photonic nature of the two traveling wave components that are the cause of the standing wave? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil. W5DXP wrote:
"Unfortunately, I must disagree (very slightly) with Kraus." I had invited readers to the helical antenna pages of Kraus to support my wave advance comparison to the progress of a threaded bolt. I had looked at page 229 in the 3rd edition with its Figs. 8-8 and 8-9 or at similar figures in an earlier edition. Upon looking agin, I still believe the figs. support my bolt comparison. In any case, I`d study long and hard before sarguing with Kraus. Best regards, Richard Harrison, KB5WZI |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
"Fig. 7-19 is certainly interesting." Jim`s cryptic statement sent me on a search. Eureka! My 1950 version of Kraus has that Fig. 7-19 on page 193. It shows propagarion velocities found by several researchers as a function of helix circumference. Phase velocity is the velocity at which a point of constant phase is propagated in a progressive (traveling) sinusoidal wave. Best regards, Richard Harrison, KB5WZI |
Phase Shift through a 75m Texas Bugcatcher Coil
Richard Harrison wrote: Cecil. W5DXP wrote: "Unfortunately, I must disagree (very slightly) with Kraus." I had invited readers to the helical antenna pages of Kraus to support my wave advance comparison to the progress of a threaded bolt. I had looked at page 229 in the 3rd edition with its Figs. 8-8 and 8-9 or at similar figures in an earlier edition. Upon looking agin, I still believe the figs. support my bolt comparison. In any case, I`d study long and hard before sarguing with Kraus. Best regards, Richard Harrison, KB5WZI I didn't quite grasp the purpose of your bolt comparison, Richard. The only limits Kraus puts on helices is that they are helical - anything between a flat single turn loop at one limit and a straight line at the other. 73, ac6xg |
Phase Shift through a 75m Texas Bugcatcher Coil
Richard Harrison wrote:
Cecil. W5DXP wrote: "Unfortunately, I must disagree (very slightly) with Kraus." I had invited readers to the helical antenna pages of Kraus to support my wave advance comparison to the progress of a threaded bolt. I had looked at page 229 in the 3rd edition with its Figs. 8-8 and 8-9 or at similar figures in an earlier edition. Upon looking agin, I still believe the figs. support my bolt comparison. In any case, I`d study long and hard before arguing with Kraus. No doubt, your bolt comparison is valid when each turn on the "coil" is one wavelength long. But what happens when each turn is 0.006 wavelength? Do you reckon something might change? Hopefully, I am not disagreeing with Kraus. It appears that the question is: Does Kraus' one wavelength per turn helical antenna have the same VF as a 75m Texas Bugcatcher loading coil? Kraus' own graph shows that if one varies the turn circumference, the phase velocity is not a linear correspondence. I would suggest that lack of linear correspondence occurs in the 75m Texas Bugcatcher coil. We cannot tell what the exact phase difference would be at 0.006 wavelength per turn, but the trend seems obvious to me. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Richard Harrison wrote:
Eureka! My 1950 version of Kraus has that Fig. 7-19 on page 193. It shows propagation velocities found by several researchers as a function of helix circumference. Phase velocity is the velocity at which a point of constant phase is propagated in a progressive (traveling) sinusoidal wave. My 3rd edition, shows the lack of a 1:1 correspondence between the circumference of a turn and the phase velocity of that turn. If one projects Kraus' graph back to 0.006 wavelength for the circumference of the coil, the lack of correspondence should become pretty large, maybe even matching my reported EZNEC results? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil, W5DXP wrote:
"---are standing waves electromagnetic waves?" According to Tigertek they are not. Photons are massless at rest. They cease to exist. Waves made of photons thus don`t exist if they are not in motion. A real electromagnetic wave must be moving to exist. Check out Tigertek`s fact of the day. Best regards, Richard Harrison, KB5WZI |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
I didn't quite grasp the purpose of your bolt comparison, Richard. The only limits Kraus puts on helices is that they are helical - anything between a flat single turn loop at one limit and a straight line at the other. My 3rd edition only shows coil circumferences between 0.6 and 1.5 wavelengths. But the relative phase velocity is 1.0 when the circumference is 1.1 wavelength and the pitch angle is 5 degrees. If the relative phase velocity is 1.0 when the circumference is 1.1 WL, doesn't that imply a change in VF away from a straight piece of wire? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Richard Harrison wrote:
Cecil, W5DXP wrote: "---are standing waves electromagnetic waves?" According to Tigertek they are not. Photons are massless at rest. They cease to exist. Waves made of photons thus don`t exist if they are not in motion. A real electromagnetic wave must be moving to exist. Check out Tigertek`s fact of the day. I agree that there is a logical contradiction between standing waves and electromagnetic waves. Too bad the people using standing wave current for measuring phase don't realize that. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
"I don`t quite grasp the purpose of your bolt comparison, Richard." My point was that the signal is guided by the wire on the coil and isn`t instantly transported by induction from one end of the coil to the other. How long it takes the signal to travel the length of the coil depends on the length of wire in the coil as well as the velocity factor of the wave on the wire in the coil. If it were not so, Terman`s explanation of the traveling wave tube (TWT) would not be valid. But, GTE Lenkurt gives a similar explanation in its "Demodulator" of the TWT. They manufactured TWT amplifiers and surely knew how they worked. A coil is a coil whether it is used in a traveling wave tube or used to load an antenna. The velocity factors are surely a function of coil dimensions as illustrated by the research results given by Kraus in Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me. There is probably more research which explains such variations. Best regards, Richard Harrison, KB5WZI |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote: Jim Kelley wrote: I didn't quite grasp the purpose of your bolt comparison, Richard. The only limits Kraus puts on helices is that they are helical - anything between a flat single turn loop at one limit and a straight line at the other. My 3rd edition only shows coil circumferences between 0.6 and 1.5 wavelengths. But the relative phase velocity is 1.0 when the circumference is 1.1 wavelength and the pitch angle is 5 degrees. If the relative phase velocity is 1.0 when the circumference is 1.1 WL, doesn't that imply a change in VF away from a straight piece of wire? Hi Cecil, The entire point of Richard's citation is that VF is a function of pitch to circumference ratio. It explains the very thing that you need to support your argument about phase delay across a coil. It's what I meant when I said "I still think it would be prudent to explore and understand the precise nature of the delay through the coil more thoroughly before making too many assumptions about this." Beyond that, I don't understand the question. Kraus is pretty explicit. I didn't see much need to read between the lines. But all I have to look at is the scanned version on the web that someone posted a link to a week or so ago. You should send Richard H. a fruit basket. Who woulda thought to look under Helical Antennas. :-) 73, Jim AC6XG |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
The entire point of Richard's citation is that VF is a function of pitch to circumference ratio. It explains the very thing that you need to support your argument about phase delay across a coil. Does "circumference" mean the circumference of the coil or is it the actual wire length once around the helix? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
But all I have to look at is the scanned version on the web that someone posted a link to a week or so ago. Unfortunately, it has been removed. Did you save it? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
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Phase Shift through a 75m Texas Bugcatcher Coil
On May 9, 11:49 am, Cecil Moore wrote:
Jim Kelley wrote: Tom doesn't even have a dog in this fight as far as I know. Tom's web page is in this dog fight. Tom has posted hundreds of postings in the past in support of his instantaneous current with no phase shift through a loading coil. He even "measured" the phase shift through a large coil at 5 nS. Of course, his "measurement" was made with standing- wave current which doesn't change phase. Then let me put it to you this way. I don't have a dog in your fight with him. Why don't you go tell it to him? 73, Jim AC6XG |
Phase Shift through a 75m Texas Bugcatcher Coil
On May 9, 2:54 pm, Cecil Moore wrote:
I agree that there is a logical contradiction between standing waves and electromagnetic waves. If there is, then there must also be contradiction between traveling waves and destructive interference, and between two dissonant notes and the beat they create. They are all simply the result of superposition. Two things happening at the same time in the same place with one result. But nothing more. Take two sound waves of identical frequency and superpose them. The result is a single waveform. Now decrease the frequency of one just a bit. They still superpose to create a single waveform but now the net amplitude varies with time according to the difference in frequency. Decrease the frequency even more. We still have a single waveform, and the beat frequency may now be too rapid to easily discern, but now we can begin to discern two distinct pitches. Look at it on a spectrum analyzer and we can see each of the two frequencies individually. Yet all we see on the oscilloscope is one waveform. Is that the contradiction? 73, Jim AC6XG |
Phase Shift through a 75m Texas Bugcatcher Coil
On May 9, 4:28 pm, Cecil Moore wrote:
Jim Kelley wrote: The entire point of Richard's citation is that VF is a function of pitch to circumference ratio. It explains the very thing that you need to support your argument about phase delay across a coil. Does "circumference" mean the circumference of the coil or is it the actual wire length once around the helix? -- 73, Cecil http://www.w5dxp.com 2*Pi*radius ac6xg |
Phase Shift through a 75m Texas Bugcatcher Coil
On May 9, 3:27 pm, (Richard Harrison) wrote:
Jim Kelley wrote: "I don`t quite grasp the purpose of your bolt comparison, Richard." My point was that the signal is guided by the wire on the coil and isn`t instantly transported by induction from one end of the coil to the other. How long it takes the signal to travel the length of the coil depends on the length of wire in the coil as well as the velocity factor of the wave on the wire in the coil. If it were not so, Terman`s explanation of the traveling wave tube (TWT) would not be valid. But, GTE Lenkurt gives a similar explanation in its "Demodulator" of the TWT. They manufactured TWT amplifiers and surely knew how they worked. A coil is a coil whether it is used in a traveling wave tube or used to load an antenna. The velocity factors are surely a function of coil dimensions as illustrated by the research results given by Kraus in Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me. There is probably more research which explains such variations. Best regards, Richard Harrison, KB5WZI Ok. But what I was asking is what does any of that have to do with a bolt? 73, Jim AC6XG |
Phase Shift through a 75m Texas Bugcatcher Coil
On 9 May 2007 23:29:28 -0700, Jim Kelley wrote:
On May 9, 3:27 pm, (Richard Harrison) wrote: Jim Kelley wrote: "I don`t quite grasp the purpose of your bolt comparison, Richard." My point was that the signal is guided by the wire on the coil and isn`t instantly transported by induction from one end of the coil to the other. How long it takes the signal to travel the length of the coil depends on the length of wire in the coil as well as the velocity factor of the wave on the wire in the coil. If it were not so, Terman`s explanation of the traveling wave tube (TWT) would not be valid. But, GTE Lenkurt gives a similar explanation in its "Demodulator" of the TWT. They manufactured TWT amplifiers and surely knew how they worked. A coil is a coil whether it is used in a traveling wave tube or used to load an antenna. The velocity factors are surely a function of coil dimensions as illustrated by the research results given by Kraus in Fig.7-19 in the 1950 edition of "Antennas". The variation surprises me. There is probably more research which explains such variations. Best regards, Richard Harrison, KB5WZI Ok. But what I was asking is what does any of that have to do with a bolt? The travel of one turn of a point at the radius (helical distance) in relation to the travel of the same point in the depth (the linear displacement after 360 degrees of the turn) is related to pitch. A simple mechanical relationship. This is the bolt. The signal flowing in the helix modulates a beam traveling within the axis of the helix to impose its frequency upon it (amplification/oscillation) through the pitch. This is the TWT. The helical distance is supposed to express the linear completion of the truncated 90 degrees of a quarterwave radiator. This is for the loading coil. There is no obvious correlation between the mechanical description, the harmonic relation of the TWT and the degree relation of the loading coil beyond the simple, visual metaphor which doesn't really add any quid-pro-quo. What is missing for the TWT is the necessary correlation of the beam drift velocity which is wholly lacking from the bolt metaphor. To say that the coil replaces the missing degrees of the truncated quarterwave has likewise been so sloppily handled in the past, that 60-70% error brushed aside to prove equality provokes "so what?" 73's Richard Clark, KB7QHC |
Phase Shift through a 75m Texas Bugcatcher Coil
"Jim Kelley" wrote in message ps.com... On May 9, 2:54 pm, Cecil Moore wrote: I agree that there is a logical contradiction between standing waves and electromagnetic waves. If there is, then there must also be contradiction between traveling waves and destructive interference, and between two dissonant notes and the beat they create. They are all simply the result of superposition. Two things happening at the same time in the same place with one result. But nothing more. Take two sound waves of identical frequency and superpose them. The result is a single waveform. Now decrease the frequency of one just a bit. They still superpose to create a single waveform but now the net amplitude varies with time according to the difference in frequency. Decrease the frequency even more. We still have a single waveform, and the beat frequency may now be too rapid to easily discern, but now we can begin to discern two distinct pitches. Look at it on a spectrum analyzer and we can see each of the two frequencies individually. Yet all we see on the oscilloscope is one waveform. Is that the contradiction? 73, Jim AC6XG No, Its an illusion. The same thing happens when you view an AM signal. On an oscilloscope the pattern you see may give you the impression that the carrier is changing in amplitude with the modulation. Perhaps standing waves are this same type of illusion. Jimmie |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
Then let me put it to you this way. I don't have a dog in your fight with him. Why don't you go tell it to him? I already did. But let's extend your logic to John Kraus. He doesn't have a dog in this fight either. Why is it OK to quote Kraus and not OK to quote w8ji? -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
Cecil Moore wrote: I agree that there is a logical contradiction between standing waves and electromagnetic waves. Is that the contradiction? You obviously misunderstood what I was trying to say so let me expand my statement: Since contradictions do not exist in reality, any apparent contradiction between standing EM waves and traveling EM waves has to exist only in the human mind. There is no contradiction in the real world. The photons in a standing wave are moving at the speed of light, c*VF, not standing still in the standing wave. Believing that the component traveling waves cease to exist is the contradiction and cannot occur in reality. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
2*Pi*radius Sorry, I'm a little handicapped since I have never seen "Figure 7-19" and it has been removed from the web site. -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote:
... If that were true, Intel could speed up its computer buses by adding a 75m Texas Bugcatcher coil to each data/control line, i.e. it is a ridiculous assertion. Cecil: This whole discussion has been interesting. I have loved the debate and analysis ... krist, you guys keep this up and I just may end up finding ham radio fun again! Let's just remember to all shake hands when this is done :-) Warmest regards, JS |
Phase Shift through a 75m Texas Bugcatcher Coil
John Smith I wrote:
Let's just remember to all shake hands when this is done :-) Gurus don't shake hands because they might get contaminated by the outside world. :-) -- 73, Cecil http://www.w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
On May 10, 6:29 am, "Jimmie D" wrote:
No, Its an illusion. The same thing happens when you view an AM signal. On an oscilloscope the pattern you see may give you the impression that the carrier is changing in amplitude with the modulation. Perhaps standing waves are this same type of illusion. I am unsure why you would call this an illusion. The modulated waveform can be accurately described by (f(t)+1)*cos(2*pi*fc*t) where f(t) is the modulating signal from which it is easy to discern that the amplitude is changing with the modulation. There is often more than one way to describe an observation and the existence of this description in no way detracts from the alternative which has a carrier plus and minus the modulating signal. Many of the arguments here do seem to be of the form "You say tomatoe and I say tomatoe", but the important point is that the appropriate description be used for the problem at hand. Filter design is probably better done with the latter, while modulators and envelope detectors are likely better analyzed with the former. But I find no reason to declare one to be less of an illusion than the other. You are correct though; this is exactly like the arguments about "standing waves" and "travelling waves". The mathematical expressions for each accurately describe the voltage and current distribution on the line, yet some wish to argue that one description is more real than the other. They are equally real and equally illusions. The important point is to choose the one that best helps solve whatever problem is at hand and not to get carried away with a belief that one is more real than the other. ....Keith |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote:
Jim Kelley wrote: Cecil Moore wrote: I agree that there is a logical contradiction between standing waves and electromagnetic waves. Is that the contradiction? You obviously misunderstood what I was trying to say so let me expand my statement: Since contradictions do not exist in reality, any apparent contradiction between standing EM waves and traveling EM waves has to exist only in the human mind. There is no contradiction in the real world. The photons in a standing wave are moving at the speed of light, c*VF, not standing still in the standing wave. Believing that the component traveling waves cease to exist is the contradiction and cannot occur in reality. Cecil, Why do you seem to believe that bringing photons into the discussion adds any light? (pun intended) Does the word "photon" sound more hifalutin than "wave"? It is instructive to follow the lead of Kraus. In the second edition of "Antennas", on page 19, Kraus notes, "In simplest terms an antenna converts photons to currents or vice versa." He then goes on to write nearly 900 pages, and it is not apparent that he ever again mentions "photon". I did not find any cases in a quick review. Have you ever seen any technical treatment of HF radiation that actually used photons in the equations? 73, Gene W4SZ |
Phase Shift through a 75m Texas Bugcatcher Coil
Gene Fuller wrote:
Why do you seem to believe that bringing photons into the discussion adds any light? (pun intended) Does the word "photon" sound more hifalutin than "wave"? Using "photons" instead of "EM waves" makes things a little more obvious. While "standing EM waves" may imply EM waves that are standing still, "standing photons" are obviously impossible. Photons cannot stand still. EM waves cannot stand still for the same reason. A "standing EM wave" is a human abstraction that doesn't really exist in reality. The only people with something to gain by objecting to the use of "EM waves" and "photons" interchangeably are the people trying to hoodwink the uninitiated into believing that photons can stand still. :-) -- 73, Cecil, w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Keith Dysart wrote:
On May 10, 6:29 am, "Jimmie D" wrote: No, Its an illusion. The same thing happens when you view an AM signal. On an oscilloscope the pattern you see may give you the impression that the carrier is changing in amplitude with the modulation. Perhaps standing waves are this same type of illusion. I am unsure why you would call this an illusion. The modulated waveform can be accurately described by (f(t)+1)*cos(2*pi*fc*t) where f(t) is the modulating signal from which it is easy to discern that the amplitude is changing with the modulation. There is often more than one way to describe an observation and the existence of this description in no way detracts from the alternative which has a carrier plus and minus the modulating signal. Many of the arguments here do seem to be of the form "You say tomatoe and I say tomatoe", but the important point is that the appropriate description be used for the problem at hand. Filter design is probably better done with the latter, while modulators and envelope detectors are likely better analyzed with the former. But I find no reason to declare one to be less of an illusion than the other. You are correct though; this is exactly like the arguments about "standing waves" and "travelling waves". The mathematical expressions for each accurately describe the voltage and current distribution on the line, yet some wish to argue that one description is more real than the other. They are equally real and equally illusions. The important point is to choose the one that best helps solve whatever problem is at hand and not to get carried away with a belief that one is more real than the other. ...Keith Thank you for nicely elucidating the distinctions in emphasis between "science" and engineering, Keith. I believe a perfect (just to keep this at an abstract level) SA reveals the underlying reality of the modulated AM carrier. An oscilloscope displays a waveform that can be mathematically derived from the underlying reality. On the scope, it is produced by electronically combining three (assumed) sine waves. Without the mathematical or electronic operations, I suggest the waveform displayed by the scope does not exist. Mathematical equivalence between time and frequency domains does not demonstrate (in my humble opinion) a duality in the underlying reality. In reality, there are only the original three frequencies which can be demonstrated by selective filtering. Whether the oscilloscope waveform is an illusion is perhaps a semantic issue since it is an artifact constructed from, and convertible at will back into the three continuously existing sine waves which never surrender their independent qualities. Quite a bit of difference from transmission line standing waves, no? My $02. Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Phase Shift through a 75m Texas Bugcatcher Coil
Gene, W4SZ wrote:
"It is instructive to follow the lead of Kraus. In the second edition of "Antennas", on page 19, Kraus notes, "In simplest terms an antenna converts photons to currents or vice versa." In the paperback 3rd edition, which I think Cecil has, I was pleased to find a similar quotation at the top of page 12. Best regards, Richard Harrison, KB5WZI |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote: Jim Kelley wrote: Cecil Moore wrote: I agree that there is a logical contradiction between standing waves and electromagnetic waves. Is that the contradiction? There is no contradiction in the real world. My point exactly. ac6xg |
Phase Shift through a 75m Texas Bugcatcher Coil
On May 10, 11:25 am, Chuck wrote:
Thank you for nicely elucidating the distinctions in emphasis between "science" and engineering, Keith. I believe a perfect (just to keep this at an abstract level) SA reveals the underlying reality of the modulated AM carrier. Let me offer two examples. I turn on my RF signal generator. I turn up the RF Level, then I turn it down, then up, then down, .... I can see this varying RF level on my oscilloscope (slow sweep), and even on my RF voltmeter. I know I am varying the level of the RF. But I also know that I could produce exactly the same output by adding 3 signals of slightly different frequency together. I am not at all comfortable with saying the latter is 'real' while the former isn't. I know I was varying the RF Level. Or, I turn on my RF signal generator with some level for 1 minute. I turn it off for a week. I turn it on for one minute. I turn it off. I compute the Fourier transform. I can create exactly the same signal by adding all the Fourier terms, extending forward and backwards in time, forever. But is this more real than: I turn it on, then off, then on, then off? Using these examples, I can find no reason why the multiple signal explanation is more real than the varying amplitude explanation. And I suggest, that for these two cases, the varying amplitude explanation is probably more useful. ....Keith |
Phase Shift through a 75m Texas Bugcatcher Coil
Jim Kelley wrote:
Cecil Moore wrote: There is no contradiction in the real world. My point exactly. My point exactly first! Contradictions exist *only* in human minds. -- 73, Cecil, w5dxp.com |
Phase Shift through a 75m Texas Bugcatcher Coil
Cecil Moore wrote:
Gene Fuller wrote: Why do you seem to believe that bringing photons into the discussion adds any light? (pun intended) Does the word "photon" sound more hifalutin than "wave"? Using "photons" instead of "EM waves" makes things a little more obvious. While "standing EM waves" may imply EM waves that are standing still, "standing photons" are obviously impossible. Photons cannot stand still. EM waves cannot stand still for the same reason. A "standing EM wave" is a human abstraction that doesn't really exist in reality. The only people with something to gain by objecting to the use of "EM waves" and "photons" interchangeably are the people trying to hoodwink the uninitiated into believing that photons can stand still. :-) -- 73, Cecil, w5dxp.com Cecil, There seems to be a pretty fundamental disconnect here. Waves don't create radiation; photons don't create radiation; accelerating charges do create radiation. You seem to be placing some sort of restriction on the motion of those charges. They can move or stand still as they please. Some folks around here appear to think that standing waves are totally inert, and therefore totally useless or even fictitious. There are most definitely accelerating charges in a standing wave, and that accelerated charge generates the desired radiation. Call it "sloshing" if you wish, but it still works. What difference does it make if the wave on the antenna and the radiated wave in space can be defined as photons? Answer: None whatsoever, and there is not even any insight gained into the radiation mechanism at HF. In case there is any doubt, let me say it again; Adding photons into the discussion of HF radiation adds absolutely nothing but confusion. 73, Gene W4SZ |
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