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Quarterwave vertical with radials
Richard Clark wrote:
On Mon, 10 Jul 2006 17:57:42 -0400, John Popelish wrote: I meant that half as many photons are produced, compared to the full dipole antenna that produces the same fields above the center line. Hi John, So, proceeding along your avowed lines of Photons, one of several questions: Presuming 100W radiated, how many photons would that be so that we can talk about them by halves. Well, you couldn't be radiating 100 watts in both cases if the field strength is the same above the center line, but half the field is missing in one of the cases. But regardless of the radiating structure, if 100 watts at 40 M is being radiated, you are launching about 2*10^28 photons per second. Yes, that is perhaps unfair, however it demonstrates how easily the discussion can tumble for lack of quantifiables such as that original offering of 100W. Hence the stipulation that the field strength above the centerline being constant, rather than the radiated power. I missed that we were only talking about a case of radiating 100 watts. Should we discuss how infinitesimal the energy is in a 40M photon? (Easily accounts for why so many are needed for that same 100W.) Not much to discuss. I don't do such calculations often, but I get about 5*10^-27 joule per photon. What do you calculate their energy to be? No, I suppose not. Do you have some point? Want to get into the problems of diffraction with object lenses that measure less than a wavelength of the photon? Sure. That will take us back to how an elevated radial system gives a different vertical pattern than an actual ground plane or a lossy ground does. You go first. Hard to escape, and makes a mess of describing mirrors too, especially when they are skeletal approximations as well. You have to start understanding mirrors, somewhere. Perhaps you prefer a different starting point. There are several. I can offer more thread-busters when it comes to photonics, but that is a slam dunk. Get us rolling on one ace proposition, and I will get back to you in a couple of hours. I have no idea what you are saying with these two sentences. |
Quarterwave vertical with radials
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Quarterwave vertical with radials
Richard Clark wrote:
On Mon, 10 Jul 2006 17:57:42 -0400, John Popelish wrote: I meant that half as many photons are produced, compared to the full dipole antenna that produces the same fields above the center line. Hi John, So, proceeding along your avowed lines of Photons, one of several questions: Presuming 100W radiated, how many photons would that be so that we can talk about them by halves. Yes, that is perhaps unfair, however it demonstrates how easily the discussion can tumble for lack of quantifiables such as that original offering of 100W. Should we discuss how infinitesimal the energy is in a 40M photon? (Easily accounts for why so many are needed for that same 100W.) No, I suppose not. Want to get into the problems of diffraction with object lenses that measure less than a wavelength of the photon? Hard to escape, and makes a mess of describing mirrors too, especially when they are skeletal approximations as well. I can offer more thread-busters when it comes to photonics, but that is a slam dunk. Get us rolling on one ace proposition, and I will get back to you in a couple of hours. 73's Richard Clark, KB7QHC How many photons does it take to make a Watt? 73, Tom Donaly, KA6RUH |
Quarterwave vertical with radials
Tom Donaly wrote:
How many photons does it take to make a Watt? 1/(Hz*6.63*10^-34). The lower the frequency the less energy per photon. |
Quarterwave vertical with radials
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Quarterwave vertical with radials
Reg Edwards wrote:
A pair of radials behave as a continuous dipole fed at its center via a single wire. And it radiates. If the radials are horizontal and radiating, why is there virtually no horizontally polarized radiation? -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
John Popelish wrote:
Remember, it is Cecil, not me, who demands agreement or eternal verbal torture. I don't demand agreement, John, just resolution. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Tom Donaly wrote:
wrote: Cecil Moore wrote: It's pretty easy to understand. Any two radials, 180 degrees apart and high enough, should theoretically cancel each other's radiation in the far field. Not true. How much not true? -45 DB, i.e. negligibly not true. :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Cecil Moore wrote: Funny, I don't see "fully cancel" anywhere in my posting. I probably should have said "tend to cancel". A free space vertical with horizontal radials in EZNEC has horizontal radiation more than 40 dB down from the vertical radiation. That's a high degree of cancellation. The issue is the horizontal opposing radials only have that degree of cancellation for perfectly horizontal directions. You will be able to see your statement isn't true if you place the antenna in freespace and look at pattern distortion at various elevation angles. For example, the 2-d plot is skewed 2.11 dB from being circular at - 45 and +45 degrees elevation. The skewing gets worse at larger angles from the plane of the radials. If the radials were REALLY radiating -40dB in all directions as you wrongly assume, there would NOT be significant FS change in the azimuth pattern at various elevations. You looked at horizontal radiation, but the horizontal radials peak radiation is vertically polarized and nearly off the radial's ends. (Just like in a dipole pattern.) The radials do indeed radiate enough to change the pattern a significant amount (but not at zero degrees), but the largest problem is decoupling the feedline shield. The fewer radials are used, the bigger the problem becomes. There are VERY good reasons everyone settled on four radials, and it isn't the old wive's tale about making the antenna look good. Four radials is a reasonable compromise between excessive common mode problems and tolerable common mode feedline current problems, pattern, and cost. Don't feel bad though Cecil. Many people miss this point, even card carrying Mensa members. 73 Tom |
Quarterwave vertical with radials
Reg Edwards wrote: A pair of radials behave as a continuous dipole fed at its center via a single wire. And it radiates. If the radials are horizontal and radiating, why is there virtually no horizontally polarized radiation? -- 73, Cecil ====================================== Cec, Your use of the word "virtually" indicates a weakness in your ideas on the subject. The radiation, as small as it may be, is vertically polarised. ---- Reg. |
Quarterwave vertical with radials
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Quarterwave vertical with radials
What's the matter with 3, equi-spaced radials?
Be economical. Save a radial! It looks better too. And there are no arguments about directionality. ---- Reg. |
Quarterwave vertical with radials
On Tue, 11 Jul 2006 14:35:34 +0100, "Reg Edwards"
wrote: What's the matter with 3, equi-spaced radials? Be economical. Save a radial! It looks better too. And there are no arguments about directionality. ---- Reg. Modeling such an arrangement gave no real noticeable difference between using three or four radials. Danny, K6MHE |
Quarterwave vertical with radials
Reg Edwards wrote:
Reg Edwards wrote: A pair of radials behave as a continuous dipole fed at its center via a single wire. And it radiates. If the radials are horizontal and radiating, why is there virtually no horizontally polarized radiation? -- 73, Cecil ====================================== Cec, Your use of the word "virtually" indicates a weakness in your ideas on the subject. The radiation, as small as it may be, is vertically polarised. ---- Reg. Put a number on it, Reg. Besides, you said, yourself, that Cecil is always right. 73, Tom Donaly, KA6RUH |
Quarterwave vertical with radials
Cecil Moore wrote:
Tom Donaly wrote: wrote: Cecil Moore wrote: It's pretty easy to understand. Any two radials, 180 degrees apart and high enough, should theoretically cancel each other's radiation in the far field. Not true. How much not true? -45 DB, i.e. negligibly not true. :-) That's what I thought. Sometimes, orders of magnitude are important. Otherwise, people would be worrying about the fact that they're closer to the center of the Earth in the middle of the bottom of a flat bottomed hole than they are at the edges. 73, Tom Donaly, KA6RUH |
Quarterwave vertical with radials
John Popelish wrote:
Tom Donaly wrote: How many photons does it take to make a Watt? 1/(Hz*6.63*10^-34). The lower the frequency the less energy per photon. That's joules per second, is it? 73, Tom Donaly, KA6RUH |
Quarterwave vertical with radials
Cecil Moore wrote:
John Popelish wrote: Remember, it is Cecil, not me, who demands agreement or eternal verbal torture. I don't demand agreement, John, just resolution. Resolution in who's mind? I don't demand anything. I just read, occasionally throw out a thought, and learn what I can. I accept that sometimes I will learn something that is wrong, but I just keep trying to fit the pieces together. |
Quarterwave vertical with radials
wrote:
Cecil Moore wrote: A free space vertical with horizontal radials in EZNEC has horizontal radiation more than 40 dB down from the vertical radiation. That's a high degree of cancellation. The issue is the horizontal opposing radials only have that degree of cancellation for perfectly horizontal directions. That's the issue? Something that no one has ever asserted otherwise? You will be able to see your statement isn't true if you place the antenna in freespace and look at pattern distortion at various elevation angles. For example, the 2-d plot is skewed 2.11 dB from being circular at - 45 and +45 degrees elevation. The skewing gets worse at larger angles from the plane of the radials. Just ran that test. There was 0.02 dB difference at +45 and -45. If the radials were REALLY radiating -40dB in all directions as you wrongly assume, there would NOT be significant FS change in the azimuth pattern at various elevations. There is no significant FS change according to EZNEC. You looked at horizontal radiation, but the horizontal radials peak radiation is vertically polarized and nearly off the radial's ends. (Just like in a dipole pattern.) Unfortunately for that argument, the radiating currents in a dipole are in phase, i.e. designed for maximum radiation. The radiating currents in symmetrical radials are 180 degrees out of phase, i.e. designed for minimum radiation. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Tom Donaly wrote:
John Popelish wrote: Tom Donaly wrote: How many photons does it take to make a Watt? 1/(Hz*6.63*10^-34). The lower the frequency the less energy per photon. That's joules per second, is it? A watt is a joule per second. The formula gives the number of photons per second that carry a watt (or a joule per second) once you provide the Hz (frequency). By the way, I am having second thoughts as to whether or not there should be a 2*pi factor in there, since most physics formulas deal with frequency in radians per second, not cycles per second. But the photon energy formulas usually deal with wavelength, and I have never seen one that assumes a wavelength is a radian of a cycle, rather that a full cycle, so, perhaps Hz is the correct unit. If anyone can clear this up for me, I would appreciate it. |
Quarterwave vertical with radials
On Mon, 10 Jul 2006 20:52:38 -0400, John Popelish
wrote: Not much to discuss. I don't do such calculations often, but I get about 5*10^-27 joule per photon. What do you calculate their energy to be? Hi John, Closer to 4.63 · 10^-27 joule. Not enough difference to matter. So, we are talking about a little more than 10^28 photons and when we return to your statement (or is it twice that?) I didn't mean that the mirror produces half of the total photons that are radiated. or I meant that half as many photons are produced, compared to the full dipole antenna that produces the same fields above the center line. I have to again exclaim: No, I suppose not. Further, as to your "stipulation:" the field strength above the centerline being constant, rather than the radiated power. I missed that we were only talking about a case of radiating 100 watts. It would be strange to talk about radiation without some expression of power to the antenna. 100 watts has been a cardinal value in this group for many years. Field strength is generally expressed in volts/meter. Somehow, its translation into eV to follow the photon metaphor seems rather strained. Going further with this convolution of centerline partition that relates to same fields (same?) to explain a difference is also quite odd. Would you care to elaborate on this concept of the centerline? Do you have some point? This is odder yet, you introduce the topic and ask me what my point is? My own separate observation is the introduction of photonics doesn't add much does it? Hard to escape, and makes a mess of describing mirrors too, especially when they are skeletal approximations as well. You have to start understanding mirrors, somewhere. Perhaps you prefer a different starting point. There are several. Starting with radials would seem to be in keeping with the thread. Shifting starts when you haven't finished seems to defeat the progression of where you were going. I can offer more thread-busters when it comes to photonics, but that is a slam dunk. Get us rolling on one ace proposition, and I will get back to you in a couple of hours. I have no idea what you are saying with these two sentences. No doubt. I read these same admissions with some frequency. It rarely keeps me up at nights worrying anymore. You were going to tie this all together weren't you? 73's Richard Clark, KB7QHC |
Quarterwave vertical with radials
"Dan Richardson wrote wrote: What's the matter with 3, equi-spaced radials? Be economical. Save a radial! It looks better too. And there are no arguments about directionality. ---- Reg. Modeling such an arrangement gave no real noticeable difference between using three or four radials. ========================================= Of course it didn't. That's the point I was making. The number of radials, from 1 to N, is immaterial. As N increases there will be a slight improvement in radiating efficiency. The N loss resistances are all in parallel as seen by the feedline. ---- Reg. |
Quarterwave vertical with radials
Tom Donaly wrote:
Besides, you said, yourself, that Cecil is always right. False. Reg didn't say that. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
On Tue, 11 Jul 2006 11:06:19 -0400, John Popelish
wrote: By the way, I am having second thoughts as to whether or not there should be a 2*pi factor in there, since most physics formulas deal with frequency in radians per second, not cycles per second. But the photon energy formulas usually deal with wavelength, and I have never seen one that assumes a wavelength is a radian of a cycle, rather that a full cycle, so, perhaps Hz is the correct unit. If anyone can clear this up for me, I would appreciate it. Hi John, That would be 2 pi radians per second as frequency - same thing as a cycle. For photonic interactions the classic treatment is usually with wavenumber as frequency not cycles nor radians. However, the 2 pi difference is the difference between the Planck constant represented as h, and its rational equivalent (with 2 pi divided out) of h-bar. 73's Richard Clark, KB7QHC |
Quarterwave vertical with radials
John Popelish wrote:
Cecil Moore wrote: I don't demand agreement, John, just resolution. Resolution in who's mind? In mine, of course. I am obsessive-compulsive that way. Sorry about that - it's probably a character flaw. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Reg Edwards wrote:
Of course it didn't. That's the point I was making. The number of radials, from 1 to N, is immaterial. Guess it depends upon one's definition of "immaterial". One horizontal radial will certainly radiate more horizontal radiation than two opposing horizontal radials. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Richard Clark wrote:
On Mon, 10 Jul 2006 20:52:38 -0400, John Popelish wrote: (snip) I meant that half as many photons are produced, compared to the full dipole antenna that produces the same fields above the center line. I have to again exclaim: No, I suppose not. Further, as to your "stipulation:" the field strength above the centerline being constant, rather than the radiated power. I missed that we were only talking about a case of radiating 100 watts. It would be strange to talk about radiation without some expression of power to the antenna. 100 watts has been a cardinal value in this group for many years. Field strength is generally expressed in volts/meter. Somehow, its translation into eV to follow the photon metaphor seems rather strained. Going further with this convolution of centerline partition that relates to same fields (same?) to explain a difference is also quite odd. Would you care to elaborate on this concept of the centerline? The center line I am referring to is the mirror line of the ground plane or radial group that allows a monopole to have a field pattern (both E and H) above that mirror line, that would exist there, if the antenna was a symmetrical dipole. Without the mirror effect, the field pattern of the monopole depends on the path the feed line takes away from the monopole, and any other conductive objects nearby. Since I am talking about field patterns, it seemed natural to switch from total radiated watts to field intensities and the photons that field emits and where those photons head. Do you have some point? I see that you snipped the line of nonsense you originally posted that prompted this question. You asked, "Should we discuss how infinitesimal the energy is in a 40M photon? (Easily accounts for why so many are needed for that same 100W.) No, I suppose not. " So I asked if asking a question and dismissing it made some point. This is odder yet, you introduce the topic and ask me what my point is? My own separate observation is the introduction of photonics doesn't add much does it? While amateurs may ultimately be interested in radiating power in particular directions, we are discussing the physics of the radiation process, and photonics is one way to think about that process. Hard to escape, and makes a mess of describing mirrors too, especially when they are skeletal approximations as well. You have to start understanding mirrors, somewhere. Perhaps you prefer a different starting point. There are several. Starting with radials would seem to be in keeping with the thread. Shifting starts when you haven't finished seems to defeat the progression of where you were going. The ultimate radial pattern is a solid disk. Once you understand what that does to the field pattern, you can start toward a radial wire layer, and see how, in important ways, like the ability to carry radial current, it resembles a disk. Then, you can explore how reducing the number of radials alters the approximation. I can offer more thread-busters when it comes to photonics, but that is a slam dunk. Get us rolling on one ace proposition, and I will get back to you in a couple of hours. I have no idea what you are saying with these two sentences. No doubt. I read these same admissions with some frequency. It rarely keeps me up at nights worrying anymore. I find that unsurprising. Your posts do not seem addressed to me or others, so much as to yourself. You were going to tie this all together weren't you? Probably not, since I am working through the process in my own mind. I am not the teacher so much as a student trying to learn something useful. I hope my posts generate more useful discussion from others than I have gotten from you, so far. |
Quarterwave vertical with radials
Cecil Moore wrote:
Tom Donaly wrote: Besides, you said, yourself, that Cecil is always right. False. Reg didn't say that. He said it under his breath as he was writing it to this newsgroup. 73, Tom Donaly, KA6RUH |
Quarterwave vertical with radials
Richard Clark wrote:
On Tue, 11 Jul 2006 11:06:19 -0400, John Popelish wrote: By the way, I am having second thoughts as to whether or not there should be a 2*pi factor in there, since most physics formulas deal with frequency in radians per second, not cycles per second. But the photon energy formulas usually deal with wavelength, and I have never seen one that assumes a wavelength is a radian of a cycle, rather that a full cycle, so, perhaps Hz is the correct unit. If anyone can clear this up for me, I would appreciate it. Hi John, That would be 2 pi radians per second as frequency - same thing as a cycle. For photonic interactions the classic treatment is usually with wavenumber as frequency not cycles nor radians. However, the 2 pi difference is the difference between the Planck constant represented as h, and its rational equivalent (with 2 pi divided out) of h-bar. Thank you. Makes good sense. |
Quarterwave vertical with radials
Cecil Moore wrote:
John Popelish wrote: Cecil Moore wrote: I don't demand agreement, John, just resolution. Resolution in who's mind? In mine, of course. I am obsessive-compulsive that way. Sorry about that - it's probably a character flaw. Then you also probably believe that a character flaw is an absolute, as are and evil. |
Quarterwave vertical with radials
John Popelish wrote:
Cecil Moore wrote: John Popelish wrote: Cecil Moore wrote: I don't demand agreement, John, just resolution. Resolution in who's mind? In mine, of course. I am obsessive-compulsive that way. Sorry about that - it's probably a character flaw. Then you also probably believe that a character flaw is an absolute, as are and evil. I dropped a word during editing. That should have read: Then you also probably believe that a character flaw is an absolute, as are good and evil. |
Quarterwave vertical with radials
Tom Donaly wrote:
Cecil Moore wrote: Tom Donaly wrote: Besides, you said, yourself, that Cecil is always right. False. Reg didn't say that. He said it under his breath as he was writing it to this newsgroup. If Reg actually believed that, he wouldn't argue with me so much. :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
John Popelish wrote:
Cecil Moore wrote: I am obsessive-compulsive that way. Sorry about that - it's probably a character flaw. Then you also probably believe that a character flaw is an absolute, as are (good) and evil. "If it's not a 'one' or a 'zero', it's broke." :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Ron wrote: Ok I am getting confused. You are saying that a groundplane will not work as good a a ground mounted vertical ? At what angle are you talking about? Are you more interested in working 500 miles or 6,000 miles? Ron Nope. I think the elevated ground plane is superior to the ground mount as long as it's high enough in the air to avoid excess ground loss. As far as long haul, there may not be too large a difference if each system is equal as far as ground loss. IE: a ground mount with 120 radials, and a GP at 1/2 wave high with 4 radials should show about the same efficiency. So for long haul dx, they should be fairly close in theory. But... You have a better ground/space wave with the elevated antenna. This can come in handy when talking 50-100 miles away when the band doesn't support NVIS with a dipole, etc.. When you run the elevated antenna, you must always think of height in terms of wavelength, not feet or meters. A 2 meter GP can be fairly low, and still very efficient. But not a low band GP. A half wave is a different height on each band. Being I recommend a minimum of 1/4 wave height when using only 4 radials, that can be pretty high on a lower frequency. On 40m, I ran one at 36 ft at the base of the radiator. Thats just over 1/4 wave up. If I ran the same antenna on 80m, I would have to mount it at 72 ft to have the same efficiency. About 145 ft on 160m. Soooo...If you can't go that high, you must increase the number of radials to lower the ground losses to a equal number. If you have a ground mount with 120 radials, you need about 60 radials if the antenna is at 1/8 wave. About 8-12 radials if the antenna is at 1/4 wave. About 3-4 radials if the antenna is at 1/2 wave. All these have the same appx ground losses. So you can see, if you run a 80m ground plane at 15 ft, the ground losses will be high unless you use a whole lot of radials. So in that case, it's really more practical to use the ground mount unless you don't mind all that wire in the air. But equal loss ground mount vs ground plane? I'd take the ground plane anyday... I ran one on 40m and it kicked serious butt on long haul dx. And yes, I use the verticals on the low bands for mostly long haul. I use dipoles, etc for NVIS. MK |
Quarterwave vertical with radials
One of the earlier postings suggested that the quarterwave vertical antenna
with radials was elementary and easy to understand. I have never found this antenna easy to understand. RF experts on this newsgroup cannot agree on whether i) the radials reflect the wave or ii) the field from the radials cancels out. The standard academic books show that the principle behind the vertical ground plane antenna is that the vertical radiating element emits the wave, and is reflected by the ground plane. You can view a conductor as having current pushed through it by a RF source, or the current can be induced in the conductor by the wave. This is a boundary condition in Maxwell's equations, referred to in theory of transmission lines and guided waves. You can view the radials as reflecting the wave and having current induced in them, or they can have current pushed through them by the RF source. This is probably the same thing, due to the arrangement of all antenna parts forming the antenna impedance. In image theory, the impedance comes from both the self impedance and the mutual impedance. It appears that a single counterpoise wire is connected to the RF ground side to provide a conductor for that side and be a form of dipole. If a proper RF ground is not provided, the result may be RF in the shack e.g. the RF tries to return via mains wiring. Does connecting several wires make the RF ground side less live i.e. occupying a larger area to be more of a reflector and thus dissipative? If a RF ground is live, it can be dangerous to touch it. Do you increase the area of RF ground to make it less dangerous to touch e.g. radials under a carpet when relatives and pets are about? The theory behind the quarterwave vertical is the monopole above a ground plane, where the ground plane reflects the wave emitted by the vertical. The monopole is explained using image theory. In practice, the ground plane is replaced by radials. Do the radials reflect the wave then? The reflecting element on a Yagi manages to reflect most of the wave. The reflecting element on a Yagi is a parasitic element that has an impedance to cause the wave emitted by the driven element to flow in a particular direction. A Yagi normally has only one reflector. Although the reflector is in the near field of the Yagi, can a comparison be made with the radials of a quarterwave vertical antenna? The reflector on a Yagi is usually a thin tube with lots of air (gap) around it. Even though it occupies a small area, it still manages to reflect most of the wave. Yagi has a Front to Back ratio in dB. Radials can be tuned. Some antennas have loading coils in the radials. Antenna theory is often about wires and metallic items reflecting waves, and the phase of the reflected wave. The phase of the reflected wave can be constructive or destructive, affecting the impedance of the antenna. If an antenna is mounted too close to the ground, the reflected wave cancels out the emitted wave. Because a ground plane reflects the wave, the impedance of an antenna can vary with height. Parastic elements on a Yagi have a mutual impedance to each other. Would you regard the radials on a quarterwave vertical as having a mutual impedance? The radials increase the conductivity below the radiating element, decreasing ground losses. The radials are regarded as a finite or imperfect ground plane. References: "Antenna Theory and Design" by Warren Stutzman and Gary Thiele. pages 66 to 68. Practical monopole with radial wires to simulate a ground plane. "Antenna Engineering Handbook" by Richard C. Johnson. Radials suppress currents from flowing on outside of coax. p 28. If the ground is imperfect, the perfect reflected image is mutiplied by a complex ground reflection coefficient. The ground has a mutual impedance. "Antenna Theory" by Professor Constantine Balanis. Second Edition p 165. A ground plane formed by a perfect conductor completely reflects the wave. If the ground is finite i.e. not as conductive, it still reflects the wave but not as well. The conductivity determines the quality of the reflection. |
Quarterwave vertical with radials
Cecil Moore wrote: plane of the radials. Just ran that test. There was 0.02 dB difference at +45 and -45. Run the test again more carefully. You are looking at something wrong. Perhaps you didn't look at the entire azimuth plot at 45 degrees elevation. There is a large skew with a 1/4 wl vertical over two 1/4 wl radials, and it gets worse at higher elevation numbers. |
Quarterwave vertical with radials
wrote:
There is a large skew with a 1/4 wl vertical over two 1/4 wl radials, and it gets worse at higher elevation numbers. Who said anything about two radials? I am reporting the standard model with four radials. I was away from my computer for four days over the holidays and may have missed the two radial discussion, if there was one. The radial radiation cancellation that I earlier described was based on four radials, certainly not on two. -- 73, Cecil http://www.qsl.net/w5dxp |
Quarterwave vertical with radials
Cecil Moore wrote: wrote: There is a large skew with a 1/4 wl vertical over two 1/4 wl radials, and it gets worse at higher elevation numbers. Who said anything about two radials? Actually YOU did. Several times as a matter of fact. I am reporting the standard model with four radials. I was away from my computer for four days over the holidays and may have missed the two radial discussion, if there was one. The radial radiation cancellation that I earlier described was based on four radials, certainly not on two. -- 73, Cecil http://www.qsl.net/w5dxp Here is what you said on this very thread: Cecil Moore wrote: Tom Donaly wrote: If you can bring yourself to think in terms of current directions and far field superposition of waves, this behavior shouldn't be that hard to understand. It's pretty easy to understand. Any two radials, 180 degrees apart and high enough, should theoretically cancel each other's radiation in the far field. -- 73, Cecil http://www.qsl.net/w5dxp Maybe reading one of your own posts will jog your memory a bit. In it we see you VERY CLEARLY stated two radials would cancel each other's radiation. 73 Tom |
Quarterwave vertical with radials
On Tue, 11 Jul 2006 12:36:18 -0400, John Popelish
wrote: The center line I am referring to is the mirror line of the ground plane or radial group that allows a monopole to have a field pattern (both E and H) above that mirror line, that would exist there, if the antenna was a symmetrical dipole. Without the mirror effect, the field pattern of the monopole depends on the path the feed line takes away from the monopole, and any other conductive objects nearby. Hi John, This is still rather obscure. You are not talking about a line, but yet another plane. World of difference there, but I won't dispute semantics further. Simply raise that monopole, complete with radial plane and the center line (as you call it), ABOVE the ground plane. I've already analyzed this elsewhere in conventional jargon, but here it seems Photons offer a different conclusion. Unfortunately you aren't prepared to pursue this as you admit later. The conventional analysis is perfectly capable of dealing with feed lines or by avoiding them altogether. One can certainly conspire to fail and corrupt the analysis, so avoiding distractions and placing the source in the model, at the feedpoint, removes a lot of uncertainty. Since I am talking about field patterns, it seemed natural to switch from total radiated watts to field intensities and the photons that field emits and where those photons head. Photons (as any radiation in this case) are incoherent and radiate in all directions. While amateurs may ultimately be interested in radiating power in particular directions, we are discussing the physics of the radiation process, and photonics is one way to think about that process. I am perfectly content and competent to that goal. The ultimate radial pattern is a solid disk. Once you understand what that does to the field pattern, you can start toward a radial wire layer, and see how, in important ways, like the ability to carry radial current, it resembles a disk. Then, you can explore how reducing the number of radials alters the approximation. I don't see a photon in this at all. You were going to tie this all together weren't you? Probably not, since I am working through the process in my own mind. I am not the teacher so much as a student trying to learn something useful. I hope my posts generate more useful discussion from others than I have gotten from you, so far. I have, with neutral objectivity, posed issues of diffraction. For one, the quarterwave antenna, in close proximity to a quarterwave mirror (those radials), does not present the characteristics of a point source that might render attractive solutions. Further, even a point source ray striking a quarterwave mirror suffers considerably. The long and short of it is that Photons make for an interesting discussion with regards to antennas. Unfortunately, and as you obliquely observe about me writing for myself, it seems I'm the only one willing to carry the topic. 73's Richard Clark, KB7QHC |
Quarterwave vertical with radials
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