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Wes you are off on a tangent again. Go back the the initial posting on this
thread. It says nothing about your poor antenna or even my antenna as I do not have one. It refers to gain and front to rear at the same frequency It does not refer to an actual physical antenna. None of your postings refer in any sense can be seen as a technical response that directly refutes the accuracy of what I stated. In your responces I see nothing but snide remarkes or deviation from the posed subject by introducing your personal antenna exploits with your own particular antenna which I say is at an incorrect height. There is nothing in the initiating post that refers to an actual antenna or even ones that are at an incorrect height. The true facts behind that initial posting that I had a NEC derived model with extra ordinary back to front figures which made other people suspicious including me when I posted that info on another thread. .. I was looking for answers to my findings. This post consisted solely of presenting a theoretical analysis that reflected the possibility of max gain and max front to rear could appear at the same frequency. Nobody even tried to challenge the analogy becauuse everybody believes all is known about antennas so there was no point in even to attempt to understand the given analogy. Instead snide remarks were made and diversionary tactics in changing the subject to actual antennas such as yours. The subject and question of this thread was made in the hope that technically the analogy made was incorrect and thus allows me personally to discount the accurracy of my modelling or on the other hand state they can find no fault with my analogy. What did I get ? Knee jerk reaction and mirth at the possibility that something new had possibly been found when all had taken the position that it is safe to debunk because every thing is known. Not one person itemised a particular line that gave them particular problems electing to pursue different issues that they have. and not to respond to the initial request such as you bring up your own personal anternna. And remember, in an effort to circumvent this "roast" aproach I offered to share everything I had with you but you preferred to continue with The "roast " aproach. Your antenna and your personal achievements are the same as what Roy did when he introduced his past achievements which again does nothing to vote pro or con to my theoretical analogy in a technical way. Don't you realise that other silent viewers around the world are wondering why the few are having difficulty with the question. I sure hope that there are many hams reading how the so called gurus are dismissing everything other say. Is this the new way America feels about those outside of these borders? Regards Art....KB9MZ.......XG "Wes Stewart" wrote in message ... On Thu, 10 Mar 2005 22:56:37 GMT, " wrote: Oh come on Wes look at your last posting where you poked fun at the idea of a polygon phasor array. And look at the other postings where it was obvious that many were not familiar with the same and needed more direction. Look at Roy, he admitted he knows nothing about the subject He did no such thing. Not only are you having difficulty expressing yourself, you have similar difficulty understanding what others are trying to tell you. I'm not trying to be cruel or harsh, but that's just the way it is. which when he next argues with the like of Cecil and others I will now have to think twice instead of accepting his typical riposte that he supplies. But I give Roy credit for being honest in the face of personal embarassment regarding his lack of knoweledge You say it was not necesary to provide a long convoluted pseudo treatise on vectors but many asked for it and you made a joke of the idea, Regarding front to rear occuring at the same frequency. An operator wants as much gain as possible when communicating so he does not need to resort to more power than needed. For best communication it is nice to block of interference to the rear and thus he needs best front to rear at the frequency of communication even tho it is of interest that he had better rejection at a lower frequency. The fact of the matter is that it is not the frequency being used, he has to live with a lesser value of rejection, your opinion may well be different. So if I understand you correctly ( a *really* dubious proposition) I would have much better success with my 20 meter antenna if I embraced your philosophy. My current antenna is of my design, a three-element monoband Yagi-Uda parasitic array. You can see it in the picture on qrz.com. It is an honest to goodness actual antenna. I have 310 countries confirmed on 20 meters most of them (The hard ones) worked with this antenna. All at the "too-low" height (according to you) of 45' above ground. I would be delighted to send you an EZNEC, Multinec, or NEC file that describes the antenna. The model accounts for boom to mast connection, element taper, etc. (per Leeson, "Physical Design of Yagi Antennas."), includes the stub matching feed system and appears to accurately describe the antenna to the best of my limited capability to measure it. Over the band of interest, 14.0 to 14.25 MHz., the modeled free-space FB exceeds 20 dB and the gain varies from ~ 7.9 to 8.15 dBi. The FB peaks at ~ 14.12 MHz and the gain is maximum at 8.15 dBi at 14.25 MHz. Pray tell, what operational advantage am I giving up because the gain at 14.12 MHz (the FB peak) is *only* about 8.0 dBi instead of 8.15 dBi? Now you also remarked that you do not want explanations, just the meat. I gave what you call a "treatise" that explained the theoretical underpinnings of what I have stated. It would be unwise at this point to declare success without not only having a NEC model to confirm it but also a 20 meter antenna and not say a 144 meg equivalent. Today we had snow, wind and rain so I could not complete the job.If by chance the antenna gives a third aproval i.e.Nec model then polygon discussion plus the antenna then I will forward it to RADCOM for peer review. It is at that time you can vent your displeasure that you rejected my offer to share the actual mathematical and physical findings. If you were looking for a way to undermine what I had stated then my " treatise" now arms you with the knoweledge to disprove what I have stated as it is one factor that convinces me of my origonal findings. If you need more information regarding vectors I will be happy to aid you in your quest No, I don't needed any more of your help with vectors. I wish you every success with your RADCOM paper. |
Art Unwin wrote:
"I have just come to realise that if one drew a polygon of element phases in an array and all elements were 180 degrees to its companion element and excluding the driven elemment, the max gain and max front to back will occur at the same frequency!" Would an antenna made entirely of pairs of identical out of phase elements be a good antenna? A "polygon of element phases" must refer to the resultant current in each element and their combined effect at a point (P) for example in the far field. Art must have resolved and composed vectors or phasors at some time. The resultant of any number of vectors can all add to zero or to some other number and direction. A zero sum often happens in physics when systems are in equiblirium. Newton said that any action results in an equal and opposite reaction. Application of a new force often causes no loss in equilibrium, just a corresponding added reaction. The reflected wave from an antenna may change in magnitude in proportion to an incidebt wave yet be nearly exactly equal in magnitude and 180-degrees out of phase with the incident wave, if the reflection is perfect. A polygon is a closed plane bounded by straight sides. It can represenht forces. Art asked if there were anything written about complete front to back cancellation in two radiators carrying oppositely directed signals if I understood the question. Indeed Kraus of W8JK fame has a lot to say about the possibility. Kraus writes about an "Array of Two Driven 1/2-wavelength El;ements. General Case with Equal Currents of Any Phase Relation." in his 1950 edition of "Antennas". It includes on page 294, field patterns for physical spacings and feed phasings. For example, at a spacing of 1/8-wavelength and a phasing of 135-degrees, there is complete cancellation in one direction while there is maximum radiation in the opposite direction. That`s the good news. Now the bad. On page 297 Kraus says: "However, in the flat-top (an advantage placing all elements at maximum height) antenna such losses may have considerable effect on the gain (as the feedpoint resistance is very low). Therefore, the question of losses and of radiating efficiency will be treated in this section in connection with a discussion of arrays of two closely spaced, out-of-phase elements. The term "closely-spaced" will be taken to mean that the elements are spaced 1/4 wavelength or less." Then, Kraus shows another fly in the ointment on page 300: "Hence the Q for 1/8 wavelength spacing is about four times the Q for 1/4 wavelength spacing. Very large Q indicates a large amount of stored energy near the antenna in proportion to the energy radiated per cycle. This also means that the antenna acts like a sharply tuned circuit." So much for bandwidth! Best regards, Richard Harrison, KB5WZI |
Richard
So the principle is good tho in Kraus case he used two feeds instead of one. Doing it his way with just 2 elements makes it very sensirive to frequency which obviously not a good thing as you point out. Your post does have my interest as I would like to see what gain he arrived at by placig all radiation to the front. In my case the gain just fell short of 16dbi I will look it up in the antenna books, thanks for pointing that one out Best regards Art KB9MZ......XG "Richard Harrison" wrote in message ... Art Unwin wrote: "I have just come to realise that if one drew a polygon of element phases in an array and all elements were 180 degrees to its companion element and excluding the driven elemment, the max gain and max front to back will occur at the same frequency!" Would an antenna made entirely of pairs of identical out of phase elements be a good antenna? A "polygon of element phases" must refer to the resultant current in each element and their combined effect at a point (P) for example in the far field. Art must have resolved and composed vectors or phasors at some time. The resultant of any number of vectors can all add to zero or to some other number and direction. A zero sum often happens in physics when systems are in equiblirium. Newton said that any action results in an equal and opposite reaction. Application of a new force often causes no loss in equilibrium, just a corresponding added reaction. The reflected wave from an antenna may change in magnitude in proportion to an incidebt wave yet be nearly exactly equal in magnitude and 180-degrees out of phase with the incident wave, if the reflection is perfect. A polygon is a closed plane bounded by straight sides. It can represenht forces. Art asked if there were anything written about complete front to back cancellation in two radiators carrying oppositely directed signals if I understood the question. Indeed Kraus of W8JK fame has a lot to say about the possibility. Kraus writes about an "Array of Two Driven 1/2-wavelength El;ements. General Case with Equal Currents of Any Phase Relation." in his 1950 edition of "Antennas". It includes on page 294, field patterns for physical spacings and feed phasings. For example, at a spacing of 1/8-wavelength and a phasing of 135-degrees, there is complete cancellation in one direction while there is maximum radiation in the opposite direction. That`s the good news. Now the bad. On page 297 Kraus says: "However, in the flat-top (an advantage placing all elements at maximum height) antenna such losses may have considerable effect on the gain (as the feedpoint resistance is very low). Therefore, the question of losses and of radiating efficiency will be treated in this section in connection with a discussion of arrays of two closely spaced, out-of-phase elements. The term "closely-spaced" will be taken to mean that the elements are spaced 1/4 wavelength or less." Then, Kraus shows another fly in the ointment on page 300: "Hence the Q for 1/8 wavelength spacing is about four times the Q for 1/4 wavelength spacing. Very large Q indicates a large amount of stored energy near the antenna in proportion to the energy radiated per cycle. This also means that the antenna acts like a sharply tuned circuit." So much for bandwidth! Best regards, Richard Harrison, KB5WZI |
Richard
I looked thru The ARRL antenna book and I cannot find any antenna let alone the two element phased array that showed ZERO radiation to the rear of the feed point. Is it possible you are pointing to F/B for minimum radiation where I am refering to zero front to rear: Regards Art "Richard Harrison" wrote in message ... Art Unwin wrote: "I have just come to realise that if one drew a polygon of element phases in an array and all elements were 180 degrees to its companion element and excluding the driven elemment, the max gain and max front to back will occur at the same frequency!" Would an antenna made entirely of pairs of identical out of phase elements be a good antenna? A "polygon of element phases" must refer to the resultant current in each element and their combined effect at a point (P) for example in the far field. Art must have resolved and composed vectors or phasors at some time. The resultant of any number of vectors can all add to zero or to some other number and direction. A zero sum often happens in physics when systems are in equiblirium. Newton said that any action results in an equal and opposite reaction. Application of a new force often causes no loss in equilibrium, just a corresponding added reaction. The reflected wave from an antenna may change in magnitude in proportion to an incidebt wave yet be nearly exactly equal in magnitude and 180-degrees out of phase with the incident wave, if the reflection is perfect. A polygon is a closed plane bounded by straight sides. It can represenht forces. Art asked if there were anything written about complete front to back cancellation in two radiators carrying oppositely directed signals if I understood the question. Indeed Kraus of W8JK fame has a lot to say about the possibility. Kraus writes about an "Array of Two Driven 1/2-wavelength El;ements. General Case with Equal Currents of Any Phase Relation." in his 1950 edition of "Antennas". It includes on page 294, field patterns for physical spacings and feed phasings. For example, at a spacing of 1/8-wavelength and a phasing of 135-degrees, there is complete cancellation in one direction while there is maximum radiation in the opposite direction. That`s the good news. Now the bad. On page 297 Kraus says: "However, in the flat-top (an advantage placing all elements at maximum height) antenna such losses may have considerable effect on the gain (as the feedpoint resistance is very low). Therefore, the question of losses and of radiating efficiency will be treated in this section in connection with a discussion of arrays of two closely spaced, out-of-phase elements. The term "closely-spaced" will be taken to mean that the elements are spaced 1/4 wavelength or less." Then, Kraus shows another fly in the ointment on page 300: "Hence the Q for 1/8 wavelength spacing is about four times the Q for 1/4 wavelength spacing. Very large Q indicates a large amount of stored energy near the antenna in proportion to the energy radiated per cycle. This also means that the antenna acts like a sharply tuned circuit." So much for bandwidth! Best regards, Richard Harrison, KB5WZI |
wrote:
Richard I looked thru The ARRL antenna book and I cannot find any antenna let alone the two element phased array that showed ZERO radiation to the rear of the feed point. In my ARRL Antenna Book, 15th edition, page 8-6: Two phased verticals with 1/8WL spacing and phased at 135 degrees shows a perfect cardioid with zero radiation in a direction 180 degrees from the direction of maximum gain, i.e. directly to the rear. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- |
Yes Cecil, a cardioid pattern ,which cannot produce zero radiation at the
rear 180 degrees of the feed point. Remember we started of with a figure 8 or two balloon pattern so for total reversal of radiation the front lobe must finish up as a perfect circle . Said another way, the two ballons are merged thus making a larger single balloon Best Regards Art "Cecil Moore" wrote in message ... wrote: Richard I looked thru The ARRL antenna book and I cannot find any antenna let alone the two element phased array that showed ZERO radiation to the rear of the feed point. In my ARRL Antenna Book, 15th edition, page 8-6: Two phased verticals with 1/8WL spacing and phased at 135 degrees shows a perfect cardioid with zero radiation in a direction 180 degrees from the direction of maximum gain, i.e. directly to the rear. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- |
Art, KB9MZ wrote:
"---I would like to see the gain he arrives at---." Kraus gives the W8JK close-spaced beam (spacing:1/8-wavelength) a gain of 5.8 dBi on page 552 in his 2002 3rd edition of "Antennas". A dipole in free-space has a gain of 2.14 dB over an isotropic, so the W8JK has a gain of 3.66 dBd. This makes the W8JLK comparable in gain to other 2-element beams in Arnold B. Bailey`s "TV and Other Receiving Antennas" catalog. Best regards, Richard Harrison, KB5WZI |
Art, KB9MZ wrote:
"I looked through the ARRL book and I cannot find any antenna let alone the two element phased array that showed zero radiation to the rear of the feed point." I was quoting the patterns in Kraus` 1950 edition of "Antennas" on page 294. However, there is a measured by D.C. Cleckner of Ohio State University pattern of a 3-element Yagi-Uda with more than 7 dB gain and almost zero radiation in the direction of 180-degrees from the maximum. It is on page 246. This has 0.1-wavelength spacing between elements. Best regards, Richard Harrison, KB5WZI |
A cardioid pattern has radiation in the 180 degree portion behind the feed
point Regards Art "Gene Fuller" wrote in message ... Art, Why not? The cardioid pattern from a two-element array was reported back as least as far as 1937, by the famous George H. Brown. In the ideal case (free space, no losses, etc.) the radiation directly to the rear is precisely zero. If you add various real world effects then the back lobe is not precisely zero, and this is shown in the ARRL Antenna Book referenced by Cecil. A detailed description of all of this is in Kraus' Antennas, 2nd Ed., in Chapter 11. He uses equations, and he does not mention coordination of balloon patterns, so perhaps you have another new invention. 73, Gene W4SZ wrote: Yes Cecil, a cardioid pattern ,which cannot produce zero radiation at the rear 180 degrees of the feed point. Remember we started of with a figure 8 or two balloon pattern so for total reversal of radiation the front lobe must finish up as a perfect circle . Said another way, the two ballons are merged thus making a larger single balloon Best Regards Art "Cecil Moore" wrote in message ... wrote: Richard I looked thru The ARRL antenna book and I cannot find any antenna let alone the two element phased array that showed ZERO radiation to the rear of the feed point. In my ARRL Antenna Book, 15th edition, page 8-6: Two phased verticals with 1/8WL spacing and phased at 135 degrees shows a perfect cardioid with zero radiation in a direction 180 degrees from the direction of maximum gain, i.e. directly to the rear. -- 73, Cecil http://www.qsl.net/w5dxp ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-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 =---- |
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