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Light,Lazers and HF
What is the main factor that prevents HF radiation from focussing
for extra gain? |
Light,Lazers and HF
Art Unwin wrote:
What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
On Sep 10, 8:45*pm, wrote:
Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. So my antenna which is physically small can be focussed on a dish which would provide straight line radiation or a radiation beam? Working on a single element on the ground with a optimizer instead of a half sphere I got a straight vertical line at the sides which suggested a gun barrel radiation with a perfect earth as the reflector. Gain was around 8db vertical which is why the question regarding focussing! If it was properly focussed the gain should be more. 2000 foot dish seems somewhat odd, probably based on a "straight" wavelength and not a small volume in equilibriumas the directer right? Art |
Light,Lazers and HF
On Sep 10, 9:23*pm, Art Unwin wrote:
On Sep 10, 8:45*pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. So my antenna which is physically small can be focussed on a dish which would provide straight line radiation or a radiation beam? Working on a single element on the ground with a optimizer instead of a half sphere I got a straight vertical line at the sides which suggested a gun barrel radiation with a perfect earth as the reflector. Gain was around 8db vertical which is why the question regarding focussing! If it was properly focussed the gain should be more. 2000 foot dish seems somewhat odd, probably based on a "straight" wavelength and not a small volume in equilibriumas the directer right? Art Let me ask the question another way. Whether it is believed or not, if a 80 Metre antenna was compressed to the size of a couple of shoe boxes would the dish be reduced in size accordingly? Regagards Art |
Light,Lazers and HF
"Art Unwin" wrote in message ... What is the main factor that prevents HF radiation from focussing for extra gain? HF can be focused for gain. Main factor is that it takes a big antenna to focus a signal on 3.5 MHz or so. Even a 2 or 3 element beam is too large for most people , but it has been done. To get any gain from a dish at that frequency would take a dish larger than 400 to 500 feet in diameter, maybe much larger. Hard to put that up a tower. |
Light,Lazers and HF
Art Unwin wrote:
On Sep 10, 8:45?pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
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Light,Lazers and HF
On Sep 10, 10:29*pm, Art Unwin wrote:
On Sep 10, 9:23*pm, Art Unwin wrote: On Sep 10, 8:45*pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. So my antenna which is physically small can be focussed on a dish which would provide straight line radiation or a radiation beam? Working on a single element on the ground with a optimizer instead of a half sphere I got a straight vertical line at the sides which suggested a gun barrel radiation with a perfect earth as the reflector. Gain was around 8db vertical which is why the question regarding focussing! If it was properly focussed the gain should be more. 2000 foot dish seems somewhat odd, probably based on a "straight" wavelength and not a small volume in equilibriumas the directer right? Art Let me ask the question another way. Whether it is believed or not, if a 80 Metre antenna was compressed to the size of a couple of shoe boxes would the dish be reduced in size accordingly? Regagards Art- Hide quoted text - - Show quoted text - No. The shoebox size antenna would approximate an isotropic if it did radiate. It would still have to be placed at the focal point of a very large parabola due to the size of the wave length. Such an antenna, I believe, on the island of Puerto Rico (the SETI antenna) although it is currently used primarily as a receiving antenna. That parabola is positioned to have a very high radiation angle and might not be be that good for terrestrial DX. |
Light,Lazers and HF
Roy Lewallen wrote:
wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Working backward from 47 I get a wavelength of 21 feet. -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
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Light,Lazers and HF
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Light,Lazers and HF
[Slaps self upside the head] 47 dB for a 2000 meter dish, 37 dB for a
2000 foot dish. And that's why I didn't choose bridge design for a career. . . Roy Lewallen, W7EL wrote: Roy Lewallen wrote: wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Working backward from 47 I get a wavelength of 21 feet. |
Light,Lazers and HF
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Light,Lazers and HF
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Light,Lazers and HF
On Sep 10, 11:56*pm, wrote:
On Sep 10, 10:29*pm, Art Unwin wrote: On Sep 10, 9:23*pm, Art Unwin wrote: On Sep 10, 8:45*pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. So my antenna which is physically small can be focussed on a dish which would provide straight line radiation or a radiation beam? Working on a single element on the ground with a optimizer instead of a half sphere I got a straight vertical line at the sides which suggested a gun barrel radiation with a perfect earth as the reflector. Gain was around 8db vertical which is why the question regarding focussing! If it was properly focussed the gain should be more. 2000 foot dish seems somewhat odd, probably based on a "straight" wavelength and not a small volume in equilibriumas the directer right? Art Let me ask the question another way. Whether it is believed or not, if a 80 Metre antenna was compressed to the size of a couple of shoe boxes would the dish be reduced in size accordingly? Regagards Art- Hide quoted text - - Show quoted text - No. The shoebox size antenna would approximate an isotropic if it did radiate. It would still have to be placed at the focal point of a very large parabola due to the size of the wave length. Such an antenna, I believe, on the island of Puerto Rico (the SETI antenna) although it is currently used primarily as a receiving antenna. That parabola is positioned to have a very high radiation angle and might not be be that good for terrestrial DX.- Hide quoted text - - Show quoted text - Is it possible to ploink threads based on the person who starts them? Jimmie |
Light,Lazers and HF
On Sep 11, 2:53*am, Jon Kåre Hellan wrote:
writes: Roy Lewallen wrote: wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Going a different way, I also get about 37. Aperture of a dish is the area, pi*r^2. r is about 14.2 wl, so area is about 635 sq. wl. Aperture of a dipole is 1/4 * 1/2 wl = 1/8 sq. wl. That makes gain 635/(1/8) = 635*8, i.e about 5100 or just over 37 dBd. This assumes 100 % illumination of the dish, which we won't achieve. So make it 35 dBd or so, i.e. 37 dBi. Using the o.p.'s formula, I get 36.5 dBi. * It's odd that pi is squared in the formula. The squared part must be to account for the area of the dish, which is pi*r^2. Obviously, this can has been compensated for by the choice of 'k'. Whoaaa guys............! Let us think a bit more regarding the basics presented instead of parrotting dish's as used in the present state of the art. Isn't a dish built around phase change of a half wave dipole in inter magnetic coupling? If I have a flash light that is focussed does this wavelength aproach still apply? I thought it would be a question of action and reaction. Trow a ball against the wall and it bounces back in a reflective manner to the angle of velocity. A dish as presently used changes the phase of a given signal to reverse it's direction. In physics we can also talk about mechanical force that rebound and rebound has nothing to do with wavelength! If we consider radiation as being the projection of particles instead of wavelike oscillation then surely the size of the reflector is solely based on what can be collected from the emmitter such that it rebounds to a point or a focussed form ? I ask the question as I know nothing about the reflective phenomina of dish's tho I have visited the one in P.R. where the dish is formed with the knoweledge that the radiation spreads out according to the emmiter used and thus when it reaches the reflector the unit strength is weaker which the dish attempts to reverse by refocussing. But then I could be totally in error thus the question to the experts Best regards Art Unwin KB9MZ .. |
Light,Lazers and HF
On Thu, 11 Sep 2008 05:20:58 -0700 (PDT), JIMMIE
wrote: Is it possible to ploink threads based on the person who starts them? Hi Jimmie, If you used Forte's Agent, yes. It would be thread wide and ignore all contributors, or you could simply kill-file (what it is called) one contributor. Other reader's offer some variant of this capacity. 73's Richard Clark, KB7QHC |
Light,Lazers and HF
On Thu, 11 Sep 2008 06:18:14 -0700 (PDT), Art Unwin
wrote: If I have a flash light that is focussed does this wavelength aproach still apply? The reflector (or magnifier lens, take your pick) is on order of at least 1 centimeter. The light wavelength is on order of 500 nanometers. Ratio = 20,000:1 Beam is generally no narrower than 15 degrees. At a distance of, say, 6 feet, that beam would cover a diameter of 18 inches. Nothing like a Lazer (sic) if that is the goal. 73's Richard Clark, KB7QHC |
Light,Lazers and HF
Jon K??re Hellan wrote:
writes: Roy Lewallen wrote: wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Going a different way, I also get about 37. Aperture of a dish is the area, pi*r^2. r is about 14.2 wl, so area is about 635 sq. wl. Aperture of a dipole is 1/4 * 1/2 wl = 1/8 sq. wl. That makes gain 635/(1/8) = 635*8, i.e about 5100 or just over 37 dBd. This assumes 100 % illumination of the dish, which we won't achieve. So make it 35 dBd or so, i.e. 37 dBi. Using the o.p.'s formula, I get 36.5 dBi. It's odd that pi is squared in the formula. The squared part must be to account for the area of the dish, which is pi*r^2. Obviously, this can has been compensated for by the choice of 'k'. The k is generally called the "efficiency factor" which is supposed to account for diversions from the theoretical optimum. From what I've read, it appears most real, well constructed and fed parabolas wind up with a k of around .55, which is why I used that number. -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
Roy Lewallen wrote:
[Slaps self upside the head] 47 dB for a 2000 meter dish, 37 dB for a 2000 foot dish. And that's why I didn't choose bridge design for a career. . . Roy Lewallen, W7EL wrote: Roy Lewallen wrote: wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Working backward from 47 I get a wavelength of 21 feet. It's always dangerous to do math in public. 73, Tom Donaly, KA6RUH |
Light,Lazers and HF
On Sep 11, 10:37*am, Richard Clark wrote:
On Thu, 11 Sep 2008 06:18:14 -0700 (PDT), Art Unwin wrote: If I have a flash light that is focussed does this wavelength aproach still apply? The reflector (or magnifier lens, take your pick) is on order of at least 1 centimeter. *The light wavelength is on order of 500 nanometers. Ratio = 20,000:1 Beam is generally no narrower than 15 degrees. *At a distance of, say, 6 feet, that beam would cover a diameter of 18 inches. *Nothing like a Lazer (sic) if that is the goal. 73's Richard Clark, KB7QHC I see no basis for the inclusion of wavelengths when one is not using a straight radiator A straight radiator requires one type of reflector an array that is condensed to a smaller volume requires a reflector that is based on the propagation from that radiator. If propagation flares out then you can calculate dish size via WL. If propagation is of a different form then the dish must be designed accordingly.The important factor as I see it is the mode of propagation and what area is required at a distance to account for tha propagation mode. If one starts with a lazer then the reflecting surface need not be larger than the initiating beam area assuming zero scattering. Your thinking is based solely on the state of the art via reading matter. You need to go back in physics to the four forces of the standard model to analyse this question on the basis of the unification theory which is all conclusive where one can determine relative ejection paths from the radiator. The latter may well gyrate to WL I suppose |
Light,Lazers and HF
On Sep 10, 10:56*pm, wrote:
On Sep 10, 10:29*pm, Art Unwin wrote: On Sep 10, 9:23*pm, Art Unwin wrote: On Sep 10, 8:45*pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. So my antenna which is physically small can be focussed on a dish which would provide straight line radiation or a radiation beam? Working on a single element on the ground with a optimizer instead of a half sphere I got a straight vertical line at the sides which suggested a gun barrel radiation with a perfect earth as the reflector. Gain was around 8db vertical which is why the question regarding focussing! If it was properly focussed the gain should be more. 2000 foot dish seems somewhat odd, probably based on a "straight" wavelength and not a small volume in equilibriumas the directer right? Art Let me ask the question another way. Whether it is believed or not, if a 80 Metre antenna was compressed to the size of a couple of shoe boxes would the dish be reduced in size accordingly? Regagards Art- Hide quoted text - - Show quoted text - No. The shoebox size antenna would approximate an isotropic if it did radiate. It would still have to be placed at the focal point of a very large parabola due to the size of the wave length. Such an antenna, I believe, on the island of Puerto Rico (the SETI antenna) although it is currently used primarily as a receiving antenna. That parabola is positioned to have a very high radiation angle and might not be be that good for terrestrial DX. The antenna at PR has a stable reflector and a moveable receiver thus the take off angle depends on the angular position of the receiver and the center of the reflector. The receiver is moved regularly so the sky can be traversed for listening. This was the idea when the antenna was set up initialy by Princeton University before they gave up possesion of it. With respect to WL no facts have been presented to support that fact. If you go back to the arbitrary border analysis a force thru the paper of the center of the border will present resultant forces around the outside of the border representing ripples on water in wave like fashion, that does not correlate to the ejection of a particle thru a fissure in the border. Mixing apples and oranges no less Nuf said |
Light,Lazers and HF
On Sep 10, 10:05*pm, wrote:
Art Unwin wrote: On Sep 10, 8:45?pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: Not so!, That is totally depended on the conditions assumed or assumptions made such as the shape and size of the emmitter from which scattering of radiation can be calculated i.e. the shape of the cone if the scattering is confined to a specific angle. If radiation is determined from all four forces of the standard model then the radiator can be any size, shape or elevation as long as it is in equilibrium, thus the "weak" force must be taken into consideration. Period . This also means one must think beyond the books where radiation is a mystery and not fully understood by the masses. Progress can only be made by following the Universal laws via first principles and not by selected extractions of formula from reading matter. Don't they parrot that in the Universities of the U.S.A.? Best regards unless you are in a nasty mood Art Unwin KB9MZ..........xg G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
JIMMIE wrote:
... Is it possible to ploink threads based on the person who starts them? Jimmie Thunderbird, with the addition of the addon "right click ignore" will pretty much do what you want; however, you must right-click and pick ignore for every thread you wish to ignore--a very minor inconvenience ... Regards, JS -- loudobbs.com -- you do have the power to be informed; but, first you have to use it. |
Light,Lazers and HF
Art Unwin wrote:
On Sep 10, 10:05?pm, wrote: Art Unwin wrote: On Sep 10, 8:45?pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: Not so!, Well, yes, I guess that's true as only those with an education in electromagnetics would know that. So I doubt many participants in rec.folk-dancing would know that, but this isn't rec.folk-dancing, though some posters here do seem to dance around a lot. -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
On Thu, 11 Sep 2008 09:38:46 -0700 (PDT), Art Unwin
wrote: On Sep 11, 10:37*am, Richard Clark wrote: On Thu, 11 Sep 2008 06:18:14 -0700 (PDT), Art Unwin wrote: If I have a flash light that is focussed does this wavelength aproach still apply? The reflector (or magnifier lens, take your pick) is on order of at least 1 centimeter. *The light wavelength is on order of 500 nanometers. Ratio = 20,000:1 Beam is generally no narrower than 15 degrees. *At a distance of, say, 6 feet, that beam would cover a diameter of 18 inches. *Nothing like a Lazer (sic) if that is the goal. I see no basis for the inclusion of wavelengths when one is not using a straight radiator Read your own question. There is no such thing as a "straight radiator" of light. There is everything to do with wavelength or you could never see light. 73's Richard Clark, KB7QHC |
Light,Lazers and HF
On Sep 11, 2:55*pm, Richard Clark wrote:
On Thu, 11 Sep 2008 09:38:46 -0700 (PDT), Art Unwin wrote: On Sep 11, 10:37*am, Richard Clark wrote: On Thu, 11 Sep 2008 06:18:14 -0700 (PDT), Art Unwin wrote: If I have a flash light that is focussed does this wavelength aproach still apply? The reflector (or magnifier lens, take your pick) is on order of at least 1 centimeter. *The light wavelength is on order of 500 nanometers. Ratio = 20,000:1 Beam is generally no narrower than 15 degrees. *At a distance of, say, 6 feet, that beam would cover a diameter of 18 inches. *Nothing like a Lazer (sic) if that is the goal. I see no basis for the inclusion of wavelengths when one is not using a straight radiator Read your own question. *There is no such thing as a "straight radiator" of light. *There is everything to do with wavelength or you could never see light. 73's Richard Clark, KB7QHC If you say so and are comfortable with that then stick with it ! My thoughts are with the reflector and it's design |
Light,Lazers and HF
On Sep 11, 2:05*pm, wrote:
Art Unwin wrote: On Sep 10, 10:05?pm, wrote: Art Unwin wrote: On Sep 10, 8:45?pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: Not so!, Well, yes, I guess that's true as only those with an education in electromagnetics would know that. So I doubt many participants in rec.folk-dancing would know that, but this isn't rec.folk-dancing, though some posters here do seem to dance around a lot. -- Jim Pennino Remove .spam.sux to reply. Yes Jim. Unless one accepts the weak force for what it is, what creaates it and what it does for overall vector angles discussion is moot. For instance the emmitter cannot be parallel to the axis of the reflector, it must be tilted per the recognition of the weak force otherwise the mathematic and symbols such as equal or zero are meaningless. You must begin with symetry or equilibrium. You surely must know Jim that many hams do not have an understanding of electromagnetics only on how a microphone is used or a particular part of ham radio where their interests are, The hobby is all inclusive and where one expertise does not necessarilly spill over to the other except only in the eyes of the speaker |
Light,Lazers and HF
On Sep 11, 2:55*pm, Richard Clark wrote:
On Thu, 11 Sep 2008 09:38:46 -0700 (PDT), Art Unwin wrote: On Sep 11, 10:37*am, Richard Clark wrote: On Thu, 11 Sep 2008 06:18:14 -0700 (PDT), Art Unwin wrote: If I have a flash light that is focussed does this wavelength aproach still apply? The reflector (or magnifier lens, take your pick) is on order of at least 1 centimeter. *The light wavelength is on order of 500 nanometers. Ratio = 20,000:1 Beam is generally no narrower than 15 degrees. *At a distance of, say, 6 feet, that beam would cover a diameter of 18 inches. *Nothing like a Lazer (sic) if that is the goal. I see no basis for the inclusion of wavelengths when one is not using a straight radiator Read your own question. *There is no such thing as a "straight radiator" of light. *There is everything to do with wavelength or you could never see light. 73's Richard Clark, KB7QHC If you say so and are comfortable with that then stick with it ! My thoughts are with the reflector and it's design |
Light,Lazers and HF
On Thu, 11 Sep 2008 13:21:15 -0700 (PDT), Art Unwin
wrote: Read your own question. *There is no such thing as a "straight radiator" of light. *There is everything to do with wavelength or you could never see light. If you say so and are comfortable with that then stick with it ! My thoughts are with the reflector and it's design Let's just confine this to light, wavelength, and reflection. Try looking at yourself in a full wavelength mirror. It would be somewhere between 450 and 650 nanometers wide or roughly the size of a virus or bacteria. Practicality demands a reflector vastly larger than that for simple and ordinary usage. I seriously doubt you have seen a mirror smaller than 20,000 times that size. Even so you wouldn't be able to see anything more than your eye in it - or with advanced optics, your face. Would that larger mirror have any more gain that one that was one thousandth its size? No, not to speak of in any practical sense. Texas Instruments invented the DMD for today's projection TV systems that use mirrors that small.... for one pixel of light. Their DMD chip has a vast array of at least 1000000 of these mirrors. Most of the light in the system is lost. Efficiency is thus very poor, but that is not an economic issue. In a way, it most conforms to the same issues of poor efficiency in a small radiator: most of the RF power is wasted before it gets into the sky. Unfortunately, for most practicing Hams, this is a very serious economic issue. Here's a practical challenge for the reader: Take a Christmas tree bulb of 7.5W. Employing every trick of the trade of optics, how much of that available power can you get into a 100 micron fiber optic? 73's Richard Clark, KB7QHC |
Light,Lazers and HF
Art Unwin wrote:
On Sep 11, 2:05?pm, wrote: Art Unwin wrote: On Sep 10, 10:05?pm, wrote: Art Unwin wrote: On Sep 10, 8:45?pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: Not so!, Well, yes, I guess that's true as only those with an education in electromagnetics would know that. So I doubt many participants in rec.folk-dancing would know that, but this isn't rec.folk-dancing, though some posters here do seem to dance around a lot. -- Jim Pennino Remove .spam.sux to reply. Yes Jim. Unless one accepts the weak force for what it is, what creaates it You mean the weak interaction which is often called the weak force or sometimes the weak nuclear force which is due to the exchange of W and Z bosons and which affects all left-handed leptons and quarks and whose typical field strength is 10^11 times less than that of the electromagnetic force? What about it? -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
On Sep 11, 4:05*pm, wrote:
Art Unwin wrote: On Sep 11, 2:05?pm, wrote: Art Unwin wrote: On Sep 10, 10:05?pm, wrote: Art Unwin wrote: On Sep 10, 8:45?pm, wrote: Art Unwin wrote: What is the main factor that prevents HF radiation from focussing for extra gain? Money. If you can afford to build a 20m parabola about 2,000 feet in diameter and the place to mount it, you'll get lots of gain. -- Jim Pennino Remove .spam.sux to reply. Then are you saying it is the antenna size that is the main factor?. Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: Not so!, Well, yes, I guess that's true as only those with an education in electromagnetics would know that. So I doubt many participants in rec.folk-dancing would know that, but this isn't rec.folk-dancing, though some posters here do seem to dance around a lot. -- Jim Pennino Remove .spam.sux to reply. Yes Jim. Unless one accepts the weak force for what it is, what creaates it You mean the weak interaction which is often called the weak force or sometimes the weak nuclear force which is due to the exchange of W and Z bosons and which affects all left-handed leptons and quarks and whose typical field strength is 10^11 times less than that of the electromagnetic force? What about it? -- Jim Pennino Remove .spam.sux to reply. No. You are referring to what Feynman brought about with his vector scheme which analyses the progression of partical format. The standard model of our Universe has four forces. Gravity which is the weakest The weak force a misnomer is the second weakest The electromagnetic force and the strong force. For a state of equilibrium all of these vectors must sum to zero. The weak force can be ascertained from the sum of the other vectors From Newtons law on action and reaction both the weak force and that which produces it is a combination of two forces that evolves from a single force. Thus when you apply a time varying current to a non magnetic radiator you also produce the weak force which is the Newton reaction force which is a rotating surface current which amateurs refer to as "skin depth" which is not a homogenous resistive skin but the Newton opposing current which is a requirment for equilibrium. When Yagi used a planar arrangement of parallel conductors parallel to the ground surface he does not include this weak force and just assumes that the arrangement is one opposing the gravitational pull. This is a good approximation but not totaly accurrate since the arrangement is not in equilibrium which is a requirement with respect to all the laws of the Masters including Maxwell. The inclusion of the weak force is the rotating force at right angles ie the Foucault current ala skin depth which is what a helicopter has at the rear to provide stabalization. Thus when this force vector is added to the gravitational force it tips the radiator as opposed to being equal and opposite to the gravitational force as is often surmised by physiscists. I t is this weak force that is directed away from a radiator which also produces a magnet field when in contact with a resting particle which has its own magnetic field which was imposed on entry to Earth and thus in conflict with the initial time varying field results in the parting of the ways in the form of levitation. When levitation is shown in experiments in high school you may remember the difficulty of achieving stabalization since the article levitated always want;'s to turn ala the circulating field. The above is How I see as the weak force in action with radiation tho you will not see it in books as the weak force has not been presented as I have above. Important note the two vectors of the magnetic fields imp[osed upon the partical creates a spinning motion as well as a elevating motion and it is this combination applied to a static particle that profides a straight line ejection to the particle which is straight like the bullet of a rifle and where the spin makes it impervious to gravity which is why some tem it as a anti gravity force All the above is a result of my work over the last few years and has not as yet been acknowledged as b eing correct in the scientific world unless an academic comes along with the same thinking for examination an impossibility based on the not invented here syndrome. A long answer to your question but a simple yes or no would not involve sharing which is what I alway strive for despite the loose mouths of naysayers Because of my above findings I am comfortable calling the particles neutrinos as nearly spent nuclear particals ejected from the suns border without spin which do arrive to alight on a diamagnetic material in the Universe with varying intensity according to the suns 11 year cycle Best regards Art Unwin KB9MZ.......XG |
Light,Lazers and HF
On Thu, 11 Sep 2008 15:07:37 -0700 (PDT), Art Unwin
wrote: ...the weak nuclear force which is due to the exchange of W and Z bosons and which affects all left-handed leptons and quarks and whose typical field strength is 10^11 times less than that of the electromagnetic force? The standard model of our Universe has four forces. Gravity which is the weakest The weak force a misnomer is the second weakest The electromagnetic force and the strong force. Try reading the two again. They are identical. The only difference is you don't know the magnitudes of those forces (the length of their vectors) like Jim obviously does. Gravity is abysmally pathetic where it needs several trillion tons of earth's mass to keep us glued to the surface. If you were an electron and earth was a proton, you couldn't survive being on the surface without being crushed by the staggering electromagnetic force. The Weak force, as Jim carefully explained, is only slightly more powerful than gravity - which is to say feeble to 11 decimal places. 73's Richard Clark, KB7QHC |
Light,Lazers and HF
On Sep 11, 5:33*pm, Richard Clark wrote:
On Thu, 11 Sep 2008 15:07:37 -0700 (PDT), Art Unwin wrote: ...the weak nuclear force which is due to the exchange of W and Z bosons and which affects all left-handed leptons and quarks and whose typical field strength is 10^11 times less than that of the electromagnetic force? The standard model of our Universe has four forces. Gravity which is the weakest The weak force a misnomer is the second weakest The electromagnetic force and the strong force. Try reading the two again. *They are identical. *The only difference is you don't know the magnitudes of those forces (the length of their vectors) like Jim obviously does. Gravity is abysmally pathetic where it needs several trillion tons of earth's mass to keep us glued to the surface. *If you were an electron and earth was a proton, you couldn't survive being on the surface without being crushed by the staggering electromagnetic force. The Weak force, as Jim carefully explained, is only slightly more powerful than gravity - which is to say feeble to 11 decimal places. 73's Richard Clark, KB7QHC I don't know what you are talking about At the top I stated Gravity was the weakest force .At the bottom of your post you state gravity was the weakest force and the weak force was a bit stronger, again what I said. So what are you talking about, a bunch of IFs. What exactly do you want me to confirm or deny? |
Light,Lazers and HF
There is obviously a lot of confusion between some of the posters that
need to be corrected Mention has been made of a bosun' and higgs field as something as being factual. In fact it is very contraversal an d is only a theory that has not been confirmed™ CERN experiments are trying to put something substantial behind this theory but nobody really knows the extent of a Higg field and nobody has caught a bosun' Feynman with his vectors took the notion that a additional particle combination provided mass, this at a time that neutrons were considered without mass. Feymans assumption lingers on inspite of the fact that it is now proven that neutrinos really do have mass. All of this talk is based around something that is not present on this earth, not seen thus not counted just names searching for a subject to be tagged upon. Now we come to the subject of "wave length" as in radiation , the subject of this post. Wavelength only has meaning if a radiator only has two degrees of freedom which means "straight". But a wavelength can move in many directions and elevations such that it has a shape of a sphere or worse. To talk of something of" such and such" a wavelength does not pertain to a straight line or a three dimensional shape such as a cube or sphere so the idea of refering to a wavelength as a linear length is absolutely meaningles because one is using a three dimensional object to describe a two dimensional linear dimention. And for the last one I refer to Newtons law of action and reaction. On this earth of ours there is no such thing as a single force which is why Newton refers to "action": If one tries to pull a piece of caramel apart there is not just one force at play but four fources since one must include the right angle forces that is "necking" the caramel at the center. Thus a force cannot exist in a straight line but must include a rotational force for equilibrium. It is that action which Newton is referring to and not a single straight vector The confusion comes about when Newtons laws are paraphrased as a "force" when it must state an "action" My posting is clearly placed within the Earth's boundary so talk of Quarks ,Bosun" Higgs field etc is clearly irrevalent to the subject of radiation unless it is a attempt to bait me or to create confusion about the subject of radiation when its aim should be education and debate. Art Unwin KB9MZ....xg |
Light,Lazers and HF
Art Unwin wrote:
There is obviously a lot of confusion between some of the posters that need to be corrected Only one that I've seen. Mention has been made of a bosun' and higgs field as something as Bosun? Are we in the Navy now? -- Jim Pennino Remove .spam.sux to reply. |
Light,Lazers and HF
On Sep 11, 4:02*am, Jon Kåre Hellan wrote:
writes: On Sep 10, 10:29*pm, Art Unwin wrote: No. The shoebox size antenna would approximate an isotropic if it did radiate. It would still have to be placed at the focal point of a very large parabola due to the size of the wave length. Such an antenna, I believe, on the island of Puerto Rico (the SETI antenna) although it is currently used primarily as a receiving antenna. That parabola is positioned to have a very high radiation angle and might not be be that good for terrestrial DX. I believe that hams once were allowed to use Arecibo for EME on 80m. I wonder what the used at the focal point. Assuming a yago directed to the center was impractical, next best choice would be a full wave loop (in my opinion). |
Light,Lazers and HF
On Sep 11, 9:18*am, Art Unwin wrote:
On Sep 11, 2:53*am, Jon Kåre Hellan wrote: writes: Roy Lewallen wrote: wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Going a different way, I also get about 37. Aperture of a dish is the area, pi*r^2. r is about 14.2 wl, so area is about 635 sq. wl. Aperture of a dipole is 1/4 * 1/2 wl = 1/8 sq. wl. That makes gain 635/(1/8) = 635*8, i.e about 5100 or just over 37 dBd. This assumes 100 % illumination of the dish, which we won't achieve. So make it 35 dBd or so, i.e. 37 dBi. Using the o.p.'s formula, I get 36.5 dBi. * It's odd that pi is squared in the formula. The squared part must be to account for the area of the dish, which is pi*r^2. Obviously, this can has been compensated for by the choice of 'k'. Whoaaa guys............! *Let us think a bit more regarding the basics presented instead of parrotting dish's as used in the present state of the art. Isn't a dish built around phase change of a half wave dipole in inter magnetic coupling? If I have a flash light that is focussed does this wavelength aproach still apply? *I thought it would be a question of action and reaction. Trow a ball against the wall and it bounces back in a reflective manner to the angle of velocity. A dish as presently used changes the phase of a given signal to reverse it's direction. In physics we can also talk about mechanical force that rebound and rebound has nothing to do with wavelength! * * *If we consider radiation as being the projection of particles instead of wavelike oscillation then surely the size of the reflector is solely based on what can be collected from the *emmitter such that it rebounds to a point or a focussed form ? *I ask the question as I know nothing about the reflective phenomina of dish's tho I have visited *the one in P.R. where the dish is formed with the knoweledge that the radiation spreads out according to the emmiter used and thus when it reaches the reflector the unit strength is weaker which the dish attempts to reverse by refocussing. But then I could be totally in error thus the question to the experts Best regards Art Unwin KB9MZ .- Hide quoted text - - Show quoted text - I think you cannot use the particle analogy with HF when dish size is not greater than wavelength. For a small dish at HF, the waves will simply bend around the dish and act as if it wasn't there. At much higher frequencies, particle concepts become more accurate. |
Light,Lazers and HF
On Sep 11, 12:28*pm, "Tom Donaly" wrote:
Roy Lewallen wrote: [Slaps self upside the head] 47 dB for a 2000 meter dish, 37 dB for a 2000 foot dish. And that's why I didn't choose bridge design for a career. . . Roy Lewallen, W7EL wrote: Roy Lewallen wrote: wrote: Of course. Everyone knows the gain of a parabola is directly proportional to the size in wavelengths, or: G=10*log k(pi*D/L)^2 Where G= gain in DB over an isotropic, k ~ .55 for most real parabolas, D is the diameter, and L is the wavelength (wavelength and diameter in the same units. So a 2,000 foot parabola on 20m would have just about 58db gain. Hm. I get 47. Roy Lewallen, W7EL Hmm, when I use 14 Mhz and 6 decimal places I get 37; must have fat fingered it the first time. Working backward from 47 I get a wavelength of 21 feet. It's always dangerous to do math in public. 73, * * *Tom Donaly, KA6RUH- Hide quoted text - - Show quoted text - Yes! I think it is best to just give the formula and tell the reader to calculate! |
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