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Max F/b and max gain at same freq.
I have just come to realise that if one drew a polygon of element phases in
a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art |
On Fri, 04 Mar 2005 05:41:29 GMT, "
wrote: I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art OK Art, This posting has been swinging in the wind for a couple of days now. Given that you threw your frustration in my face that no one shows any interest in it. Stop blaming them for their failure to recognize your genius and get down from Calvary - blame me instead! ;-) WTF do you mean by if one drew a polygon of element phases in a array and WTF should we care? 73's Richard Clark, KB7QHC |
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On Mon, 07 Mar 2005 01:02:18 GMT, "
wrote: It would appear that I have come across something new. No wonder no one came to this party. 73's Richard Clark, KB7QHC |
On Sun, 06 Mar 2005 17:21:26 -0800, Richard Clark
wrote: |On Mon, 07 Mar 2005 01:02:18 GMT, " wrote: | |It would appear that I have come across something new. | |No wonder no one came to this party. It could be new, but he can't tell us about, so how do we know? |
Wes,
I described a polygon of element phases where pairs of elements were equal and opposite and where the director was either alone or was joined by another element of the same phase. This polygon aproach was used often before the computor era A polygon as described above not only makes for a wide single direction lobe but enforces among other things the same frequency for both parameters i.e. gain and f/b If such a polygon can be drawn as stated above it shows that it is possible. I don't see how anything can be added to the above to emphasise the point I am making which is why I asked if anybody knew of any book references to the above. If you are not aware of the phase polygon aproach I can find you a reference. or, if you prefer; a simulated diagram of a polygon that illustrates my point . If that is beyond your ken I could also mail to you a computor compilation of phase and currents of an array that also illustrates my point. But my main question still remains a pointer to a technical article that discusses the possibility or impossibility of what I have stated. If you have a deeper interest in the subject I could supply to you alone the whole computor model of such an antenna and a photograph of the actual antenna which is for 20 meters. All I would ask for is complete privacy of what I provide as I have a further pursuit connected with the above. Regards Art Stewart" *n7ws*@ yahoo.com wrote in message ... On Sun, 06 Mar 2005 17:21:26 -0800, Richard Clark wrote: |On Mon, 07 Mar 2005 01:02:18 GMT, " wrote: | |It would appear that I have come across something new. | |No wonder no one came to this party. It could be new, but he can't tell us about, so how do we know? |
Art Unwin wrote:
"But my main question still remains a pointer to a technical article that discusses the possibility or impossibility of what I have stated." I don`t get the question, but it seems to me, Art wants to know if anyone has written of a method to make maximum gain correspond with maximum front-to-back ratio in a Yagi. I haven`t seen it. There is a third factor in the compromise, 50-ohm feedpoint (or some other convenient impedance). Kraus gives the Yagi-Uda story in "Antennas" There has been much experimentation and the tradeoffs still exist. Don`t close the patent office yet. Almost everything can be improved. Art may be implying that he thinks he has a way to make a better Yagi. I hope so. The "ARRL Antenna Book" is a good place to see where the art was at the time of publication. The Antenna Book devotes a chapter to the Yagi, No. 11 in my 19th edition. The directional patterns show a pair of troublesome sidelobes in addition to the mainlobe. It`s the sidelobes which are suppressed at the sacrifice of a little gain. Parasitic arrays are close-spaced for significant excitation. Close-spacing means close-coupling which lowers the drivepoint impedance. It`s a tradeoff again because low impedance eventually limits the antenna`s efficiency. Best regards, Richard Harrison, KB5WZI |
There's yet another tradeoff -- bandwidth, of both the pattern and the
impedance. Close spacing, in particular, reduces the range of frequencies over which the pattern is acceptable ("acceptable" being in itself subject to compromise) and over which the SWR is acceptable. But close spaced or not, it's much easier to tweak a design to work perfectly at a single frequency than make one that will retain some semblance of that perfection over a wider range of frequencies. Roy Lewallen, W7EL Richard Harrison wrote: Art Unwin wrote: "But my main question still remains a pointer to a technical article that discusses the possibility or impossibility of what I have stated." I don`t get the question, but it seems to me, Art wants to know if anyone has written of a method to make maximum gain correspond with maximum front-to-back ratio in a Yagi. I haven`t seen it. There is a third factor in the compromise, 50-ohm feedpoint (or some other convenient impedance). Kraus gives the Yagi-Uda story in "Antennas" There has been much experimentation and the tradeoffs still exist. Don`t close the patent office yet. Almost everything can be improved. Art may be implying that he thinks he has a way to make a better Yagi. I hope so. The "ARRL Antenna Book" is a good place to see where the art was at the time of publication. The Antenna Book devotes a chapter to the Yagi, No. 11 in my 19th edition. The directional patterns show a pair of troublesome sidelobes in addition to the mainlobe. It`s the sidelobes which are suppressed at the sacrifice of a little gain. Parasitic arrays are close-spaced for significant excitation. Close-spacing means close-coupling which lowers the drivepoint impedance. It`s a tradeoff again because low impedance eventually limits the antenna`s efficiency. Best regards, Richard Harrison, KB5WZI |
Yes Richard that is exactly the case.
I have a case where F/B is at the same frequency as max gain and I have not come across that before so I asked those well versed in antenna design if this had been discussed before, Yes, it is an alternative to a yagi but nowhere as simplistic to build, for that the yagi is hard to beat, As it happens the feed point impedance of less than 2:1 at 50 ohms is easily obtained across the 20 meter band , the primary design It compares to a 60 foot boom yagi and change of feed point can produce higher impedance but its beam width is not as narrow , the elevation angle for max gain (TOA) is 10 degrees which is some what lower than the norm .. I have been working on this design for some time now and have all the parts made for a actual antenna, The winter has been very harsh in the midwest but with good weather tomorrow I should be able to put it together and put it up as there is no need to use the prop pitch rotor which is hard to install in cold or blustery weather as I get older. .. The turning radius by the way is somewhat less than a tight two element yagi and is of a design where frontal side lobes have not come into play. Because of mechanical difficulties I do not see it replacing a yagi but that was not the intent in the first place, I just like to explore and experiment and try to work from first principles rather than be tied to well known paths of the past As a point of interest Roy I use 300 segments per halfwave length. to double check my designs but who knows ,it may still be a case of garbage! If the antenna is not broken then I have not tried hard enough and I have broken many antennas in my time As a point of interest I would direct you to past postings where I describe close coupling to the driven element to attain for an impedance of choice and can be adapted for use in any array.You may remember Roy checking out one of my designs on his page ( 13 elements on a 60 or 80 foot boom ) ere coupling achieved the 50 oihm feed as desired Regards Art |
Roy
I understand where you are coming from but your points are all based around a Yagi with standard feeds !. In my past postings over the years I have pointed out other methods of feeds that not only broaden the bandwidth but uses a high impedance, this done by extreme "close" coupling, in the order of a inch or so upwards to about 12 inches which I also wrote up in a patent some years ago just for kicks. I myself ,choose not to go less than 26 ohms when designing. and tho I can make them with very high impedance it is not really required as the ham bands are quite narrow. Where I really concentrate upon is to move away from "mutual" coupling ( what ever that means) which is commonly described with yagi antennas, to "close" coupling designs which is an entirely new world when dealing with feed impedances, as Richards post on coupling some months ago described so much better than I have done. Regards Art "Roy Lewallen" wrote in message ... There's yet another tradeoff -- bandwidth, of both the pattern and the impedance. Close spacing, in particular, reduces the range of frequencies over which the pattern is acceptable ("acceptable" being in itself subject to compromise) and over which the SWR is acceptable. But close spaced or not, it's much easier to tweak a design to work perfectly at a single frequency than make one that will retain some semblance of that perfection over a wider range of frequencies. Roy Lewallen, W7EL Richard Harrison wrote: Art Unwin wrote: "But my main question still remains a pointer to a technical article that discusses the possibility or impossibility of what I have stated." I don`t get the question, but it seems to me, Art wants to know if anyone has written of a method to make maximum gain correspond with maximum front-to-back ratio in a Yagi. I haven`t seen it. There is a third factor in the compromise, 50-ohm feedpoint (or some other convenient impedance). snip. Best regards, Richard Harrison, KB5WZI |
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I do not know of any designs
by K1FO, can you elaborate? Art "Tom Ring" wrote in message . .. wrote: bandwidth but uses a high impedance, this done by extreme "close" coupling, in the order of a inch or so upwards to about 12 inches which I also wrote up in a patent some years ago just for kicks. You mean like like the K1FO design? Or something else? tom K0TAR |
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On Fri, 04 Mar 2005 05:41:29 GMT, "
wrote: I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, this leaves a rather wide variety of shapes. Is this referencing vertical or horizontal elements? With the 180 degree element comparisons, I assume you are dealing with an equal number of sides on each polygon, or in case of verticals, at least an equal number of elements.. Is there any more you can tell us? -- 73 for now Buck N4PGW |
"Buck" wrote in message ... On Fri, 04 Mar 2005 05:41:29 GMT, " wrote: I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, It does! then I have used the incorrect term. In a yagi type diagram you can calculate the current and phase of each elemrnt but what one is interested in is the summation of the whole array and you can do this in the same way as you would do a vector diagram of forces. With the yagi array you would first start with the reflector and draw to scale a line reflecting both phase angle and magnitude. You then add lines in cosecutive order for all other elements in the array. The end of this 'toe to tail' some what erratic line will finish up some distance from the starting point, but this distance, if drawn, represents the phase and magnitude of the array as a whole. As a former mechanical engineer but now nothing ,I was taught the term "polygon of forces" which is a cumulative vector array but the shape did not necessarily consist of "equal "sides as you stated.. But then I am English born and it is known that Americans completely messed up the Elizabethan era language which a true cockney still adheres to , where as others in the same country have learned to talk in such a way it sounds as if they are trying to retain a marble in their mouth.without swallowing it. Regards Art this leaves a rather wide variety of shapes. Is this referencing vertical or horizontal elements? With the 180 degree element comparisons, I assume you are dealing with an equal number of sides on each polygon, or in case of verticals, at least an equal number of elements.. Is there any more you can tell us? -- 73 for now Buck N4PGW |
On Tue, 08 Mar 2005 05:29:03 GMT, "
wrote: "Buck" wrote in message .. . On Fri, 04 Mar 2005 05:41:29 GMT, " wrote: I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, It does! then I have used the incorrect term. In a yagi type diagram you can calculate the current and phase of each elemrnt but what one is interested in is the summation of the whole array and you can do this in the same way as you would do a vector diagram of forces. With the yagi array you would first start with the reflector and draw to scale a line reflecting both phase angle and magnitude. You then add lines in cosecutive order for all other elements in the array. The end of this 'toe to tail' some what erratic line will finish up some distance from the starting point, but this distance, if drawn, represents the phase and magnitude of the array as a whole. As a former mechanical engineer I am not ... You may be using a term familiar to your trade and I am unfamiliar with. I would be a layman in respect ... that could be the misunderstanding. I was trying to envision the antenna you were describing... can you imagine what I was seeing in my mind? :) but now nothing ,I was taught the term "polygon of forces" which is a cumulative vector array but the shape did not necessarily consist of "equal "sides as you stated.. But then I am English born and it is known that Americans completely messed up the Elizabethan era language which a true cockney still adheres to , where as others in the same country have learned to talk in such a way it sounds as if they are trying to retain a marble in their mouth.without swallowing it. Actually, I like the UK accents. As I believe my misunderstanding has nothing to do with the queen's English, but rather techno-speak for your trade, I will pack up my octagon shaped array of dipole antennas and gracefully move on to another topic. Good luck and I'll catch you in another thread. Buck Regards Art -- 73 for now Buck N4PGW |
Buck,
I agree with you. I too cannot figure out what Art is trying to say. However, your response containing the definition of a polygon is incorrect. There is no requirement for equal sides or angles. 73, Gene W4SZ Buck wrote: Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, this leaves a rather wide variety of shapes. |
On Tue, 08 Mar 2005 15:46:24 GMT, Gene Fuller
wrote: Buck, I agree with you. I too cannot figure out what Art is trying to say. However, your response containing the definition of a polygon is incorrect. There is no requirement for equal sides or angles. 73, Gene W4SZ Right. Webster says a plane polygon is a closed figure bounded by straight lines. No mention of number, length or angles, although it seems to me that you best have at least three sides, although Art might have a new polyglot method that uses only two. [g] Buck wrote: Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, this leaves a rather wide variety of shapes. |
A polygon which has equal sides and angles is a special case of polygon,
known as a "regular polygon". Roy Lewallen, W7EL Wes Stewart wrote: On Tue, 08 Mar 2005 15:46:24 GMT, Gene Fuller wrote: Buck, I agree with you. I too cannot figure out what Art is trying to say. However, your response containing the definition of a polygon is incorrect. There is no requirement for equal sides or angles. 73, Gene W4SZ Right. Webster says a plane polygon is a closed figure bounded by straight lines. No mention of number, length or angles, although it seems to me that you best have at least three sides, although Art might have a new polyglot method that uses only two. [g] Buck wrote: Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, this leaves a rather wide variety of shapes. |
On Tue, 08 Mar 2005 12:58:06 -0800, Roy Lewallen
wrote: A polygon which has equal sides and angles is a special case of polygon, known as a "regular polygon". I stand corrected.... Roy Lewallen, W7EL -- 73 for now Buck N4PGW |
I need to add a clarifier to this post.
If the phases and and magnitudes of the paired elements are exactly the same, then radiation to the rear is zero. In the real world this is difficult if not impossible to do. It certainly cannot be done with a yagi unless possibly, when elements are contorted to ensure pure resistance feed at the appropiate frequency However, what is possible with a alternate design is to have maximum front to back at max gain when the max gain is constant over a range of frequencies such that the max front to back which is usually a peak, can appear at a point where the gain is still at a maximum. Regards Art .........KB9MZ " wrote in message news:dySVd.30807$r55.174@attbi_s52... I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art |
Gene Fuller wrote: Buck, I agree with you. I too cannot figure out what Art is trying to say. Don't feel like the lone ranger...I've been following this thread for a week, and I still don't have a clue what he is trying to describe. 73, Gene W4SZ Buck wrote: Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) What he said.... |
Buck
If your background is not in science then it is natural that you would have difficulty with what I stated. If your background was in science then this stuff would be studied in 101 i.e from first principles. With a firm understanding of scalar quantities you are then fully armed to deal with antenna "curl" and other interesting facets of antennas. It would appear to me that many of this group do not have a science background but have got by in life because of a good memory and where knoweledge of first principles is not a requirement. Ofcourse age can take that advantage away which appears to have happened with past engineers of this group.........amazing! Regards Art "Buck" wrote in message ... On Tue, 08 Mar 2005 05:29:03 GMT, " wrote: "Buck" wrote in message . .. On Fri, 04 Mar 2005 05:41:29 GMT, " wrote: I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art Art, Your description is too vague for someone who doesn't have some form of reference (maybe this is a continuation of a discussion from elsewhere?) Anyway, since a polygon is any shape with more than two sides in which all sides and angles are equal, It does! then I have used the incorrect term. In a yagi type diagram you can calculate the current and phase of each elemrnt but what one is interested in is the summation of the whole array and you can do this in the same way as you would do a vector diagram of forces. With the yagi array you would first start with the reflector and draw to scale a line reflecting both phase angle and magnitude. You then add lines in cosecutive order for all other elements in the array. The end of this 'toe to tail' some what erratic line will finish up some distance from the starting point, but this distance, if drawn, represents the phase and magnitude of the array as a whole. As a former mechanical engineer I am not ... You may be using a term familiar to your trade and I am unfamiliar with. I would be a layman in respect ... that could be the misunderstanding. I was trying to envision the antenna you were describing... can you imagine what I was seeing in my mind? :) but now nothing ,I was taught the term "polygon of forces" which is a cumulative vector array but the shape did not necessarily consist of "equal "sides as you stated.. But then I am English born and it is known that Americans completely messed up the Elizabethan era language which a true cockney still adheres to , where as others in the same country have learned to talk in such a way it sounds as if they are trying to retain a marble in their mouth.without swallowing it. Actually, I like the UK accents. As I believe my misunderstanding has nothing to do with the queen's English, but rather techno-speak for your trade, I will pack up my octagon shaped array of dipole antennas and gracefully move on to another topic. Good luck and I'll catch you in another thread. Buck Regards Art -- 73 for now Buck N4PGW |
Good point ! But I have already checked this out even
wit "Dave Platt" wrote in message ... In article k1FXd.109090$tl3.58979@attbi_s02, wrote: I need to add a clarifier to this post. If the phases and and magnitudes of the paired elements are exactly the same, then radiation to the rear is zero. In the real world this is difficult if not impossible to do. It certainly cannot be done with a yagi unless possibly, when elements are contorted to ensure pure resistance feed at the appropiate frequency You might want to take a look at systems which use two or more directly-driven radiators (rather than a driven radiator and a parasitic element), with a chosen physical offset and phase offset between them.e phase Good point! I tried this with a radiator that was of opposite phase but the origanal feed method still came out best. That method has not been tested for other bands This is a classic way to get a 180-degree-only pattern. It's often used with vertical antennas. I took a quick glance at Arnold Bailey's "TV and other receiving antennas" text (written in 1950) and he shows a similar sort of antenna using two horizontal half-wave dipoles, connected together via a transmission line and fed at the center of the rear dipole. Very clean 180-degree pattern. This sort of arrangement might be a good starting point for your "move all of the energy from the rear lobes into the forward half" quest. You might be able to combine this sort of dual-driven-radiator unidirectional beamer with additional parasisic elements, to create more forward gain. A bunch of directors out in in the front would be the obvious choice for a first experiment But that defeats the issue where boom length can be erradicatred as an issue. There's a gotcha to this, though... the 180-degree pattern from a pair of phased radiators depends on the radiators being driven with equal currents, which (in this simple arrangement) requires that they have equal feedpoint impedances. Stick a bunch of parasitic directors out in front, and the feedpoint impedance of the forward radiator is going to change (drop, most likely) and affect the current relationship between the two radiators, and thus mess up the pattern. I can think of a couple of possible ways to compensate for this: - Matching network at the forward radiator (maybe shorten it a bit and use a hairpin inductor match)? I always require a near 50 ohm feed that does not require matching. - Tapered transmission-line section between the two radiators? - Try installing some parasitic elements behind the rear driven element... possibly in a corner-reflector arrangement? This might tweak the rear element's feedpoint Z enough to make it easier to match the two, might also help suppress any rear lobes which develop as a result of the mismatch. A corner reflector does not have true reflectors as all elements are of the same length and equaly spaced, they also carry low but similar current flow. I have my doubts as to whether all of this work will pay off with enough of an increase in forward gain, F/B ratio, cleanliness of pattern, reduction in lobes, broadening of bandwidth, etc. to be worth the effort over a classic Yagi, but I'm certainly willing to be proven wrong. This cannot beat the simplicity of a yagi. Good for you Dave, you have an open mind despite the massive studies over the years. But there is no way of convincing the masses who demand expensive trials and measurements which if conclusive ,changes the mode of attack to the method of testing, This is usually the method taken by even educated engineers who with huge experience in the field refuse to believe they could have passed over something. As for this antenna it is purely to satisfy me. Regards Art .. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
wrote:
If the phases and and magnitudes of the paired elements are exactly the same, then radiation to the rear is zero. If you rotate the elements by 90 degrees, can you make the radiation toward the ground zero? -- 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! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Interesting question Cecil, and I suspect the answer is yes
if you are refering to the array pointing upwards. If you are referring to turning the array sideways i.e vertical polarisation then I doubt rear radiation could be zero because the earth has more influence over vertical polarisation compared to horizontal at one wave length high. For instance pairs of elements could not have equality. You can ofcourse accomplish such if the array was reflective as with a dish but not with normal coupling and resonances where the focussing aproach is absent. Best regards Art "Cecil Moore" wrote in message ... wrote: If the phases and and magnitudes of the paired elements are exactly the same, then radiation to the rear is zero. If you rotate the elements by 90 degrees, can you make the radiation toward the ground zero? -- 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! 100,000 Newsgroups ---= East/West-Coast Server Farms - Total Privacy via Encryption =--- |
Dave Platt wrote:
"This is a classic way (2-element quarter-cycle phased array) to get 180 degree-only pattern. It`s often used with vertical antennas. I took a look at Arnold Bailey`s :TV and other receiving antennas" text (written in 1950) and he shows a similar sort of antenna using two horizontal half-wave dipoles, connected together via a transmission line (open-wire) and fed at the center of the rear dipole. Very clean 180 degree-only pattern." Yes. The directional patterns on pages 477 and 478 are excellent. This antenna also appears in Bailey`s catalog of antennas on page 521 as "Half-Wave Antenna and Connected Reflector". Its resistance at center frequency is 50 ohms where its gain is 4 dBd. Bandwidth is 60% for 3 dB down. I wonder why everybody isn`t using this antenna? Best regards, Richard Harrison, KB5WZI |
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This sounds like a switchable three element array that I once used
for CB ( As an alien I wasn't allowed a amateur license) I copied the design from a commercial antenna and with a switch box was able to point it in any one of three directions. The coax between them was a 1/4 wavelength I believe but the physical distance was much less than that. I believe I lost it when it iced up and broke the topsides of the vertical dipoles.. Regards Art "Richard Harrison" wrote in message ... Dave Platt wrote: "This is a classic way (2-element quarter-cycle phased array) to get 180 degree-only pattern. It`s often used with vertical antennas. I took a look at Arnold Bailey`s :TV and other receiving antennas" text (written in 1950) and he shows a similar sort of antenna using two horizontal half-wave dipoles, connected together via a transmission line (open-wire) and fed at the center of the rear dipole. Very clean 180 degree-only pattern." Yes. The directional patterns on pages 477 and 478 are excellent. This antenna also appears in Bailey`s catalog of antennas on page 521 as "Half-Wave Antenna and Connected Reflector". Its resistance at center frequency is 50 ohms where its gain is 4 dBd. Bandwidth is 60% for 3 dB down. I wonder why everybody isn`t using this antenna? Best regards, Richard Harrison, KB5WZI |
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I wonder why everybody isn`t using this antenna? .......
Because a rotatable yagi is usually better in most cases. But people do run those...Probably more set them up to be switchable, or even steerable, instead of just one direction. I ran phased dipoles on 40m, and they worked quite well. I switched direction by changing feedline lengths. Some use the "l/c" phaser boxes...But I can throw up my A4 real quick, and do about 7 dbd?? or so, in any direction. Kinda makes the phased dipoles a mute point, except for maybe the lower bands. If you connect with a harness, which I didn't do, you need to transpose the feed for the 2nd antenna. IE: reverse the feedline...That ladder line will have a single twist if I remember correctly. MK |
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O.K..O..K Seems like everybody has forgotton the basics of the polygon of
forces and other uses of vector so I will go over the basics. At the age of 14 yearsI entered the School of Engineering and Navigation where they hashed things from first principles, Since I had little schooling during those war years it gave me an accelerated course on what I had missed during those schoolless years which meant a lot of homework and I had to work like hell. From the name of the school it was evident that I would get a quick introduction on vectors for forces and navigation .. This went as follows: When you swim across a swimming pool then you can swim point to point. If you swim across a river and tried to swim point to point you finish up on the other side but down, stream thus to get to the original point of the endeavor you must swim upstream. If you are a ship or a plane it is obvious that you must have enought fuel to get from point to point so this becomes very important. Thus going back to the river swim you can draw a vector or line that follows the path you took first to cross the river. Since you have units such as time and distance you can draw that line in scalar form. Then you add on to the tail end of the line the journey upstream again in scalar form which will be something less than a 90 degree angle. If you then look back at the point that you started from it becomes obvious that when you swim across stream the angle you must follow is the angle which is shown from the beginning of the triangle to the point that you finished up. Next time you are on a plane look downwards and pick up the flight pattern of small private planes and you will see that their flight path is different from the angle projected by the fuselage All this is in accordance with Newton's law that 'every action has an equal and opposite reaction.' Now look below at my original post to what I said and you will see that I applied a scalar drawing that consisted of many scalae directions in the same way a sailing ship would do if it had to keep changing direction to get to shore. The first vector drawn for an element with known phase and current was drawn which happened to be a vertical line of known length. The next line was then added at the end to reflect the current and phase of the next element chosen and then onto the next element chosen. But this element presented a phase and current that was equal and opposite to the one previously drawn which meant that I was back to the tail end of my first vector chosen ! Thes two elements are termed destructive In fact this happened several times where vectors cancelled each other so we are just left with a singe vector in our scalar drawing .This meant to get back to the point of origin and remembering Newton's law previously alluded to the scalar drawing it represents a vector that is equal to the starting vector drawn, THE SAME PHASE and same CURRENT. Thus the polygon reflects an array where the phase is constant but the currents are ADDITIVE This represents the radiation pattern of a figure eight EXCEPT all the radiation is now to one side of the feed point and comprising of a single and larger circle. All of this reflects exactly what I stated below except I assumed that the pologon phase drawing was already known to all, for which I apologise. With NEC I constructed a model that closely followed this format though the real world did not make elements exactly equal but when I rehashed in my mind the basic priciples the polygon aproach verified that this aproach does give extraordinary front to back/rear figures that gave rise to mistrust of the softwear being used where you may remember that I commented on a model that I made and where the response was that the f/b was to high a point that had troubled me for many a month. Sorry for the long winded response which reflects what I have gone thru with my postings which apparently projected me as a total fool that gave rise to dirisive comments. Now I ask again, is there any written work that pertains to max gain and f to b/rear being on the same frequency? Best regards to all, no hard feelings Art KB9MZ................XG " wrote in message news:dySVd.30807$r55.174@attbi_s52... I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art |
Art If your question is "is there any written work that pertains to how gain and sidelobes are related", the answer is Yes. I dont know where back issues of the IRE Proceedings can be found. But, the Proceedings of the Professional Group on Antennas will have so much information on current distribution on a planer array that you may not have enough time left to read it all. The current distribution across an antenna aperature has been studdied very seriously. I am not qualified to discuss phased arrays. I am convinced that max gain will not be acheived with the same current distribution as for minimum side lobes. I realize that you write only "back lobes". But, thats a side lobe at that special angle I am rather simple minded when it comes to phased arrays. I use Referance Data For Radio Engineers as a referance book. It has alot of information on phased arrays. I suspect all the information I have has already been concidered by you. Jerry " wrote in message news:2w_Xd.52445$Ze3.8223@attbi_s51... O.K..O..K Seems like everybody has forgotton the basics of the polygon of forces and other uses of vector so I will go over the basics. At the age of 14 yearsI entered the School of Engineering and Navigation where they hashed things from first principles, Since I had little schooling during those war years it gave me an accelerated course on what I had missed during those schoolless years which meant a lot of homework and I had to work like hell. From the name of the school it was evident that I would get a quick introduction on vectors for forces and navigation . This went as follows: When you swim across a swimming pool then you can swim point to point. If you swim across a river and tried to swim point to point you finish up on the other side but down, stream thus to get to the original point of the endeavor you must swim upstream. If you are a ship or a plane it is obvious that you must have enought fuel to get from point to point so this becomes very important. Thus going back to the river swim you can draw a vector or line that follows the path you took first to cross the river. Since you have units such as time and distance you can draw that line in scalar form. Then you add on to the tail end of the line the journey upstream again in scalar form which will be something less than a 90 degree angle. If you then look back at the point that you started from it becomes obvious that when you swim across stream the angle you must follow is the angle which is shown from the beginning of the triangle to the point that you finished up. Next time you are on a plane look downwards and pick up the flight pattern of small private planes and you will see that their flight path is different from the angle projected by the fuselage All this is in accordance with Newton's law that 'every action has an equal and opposite reaction.' Now look below at my original post to what I said and you will see that I applied a scalar drawing that consisted of many scalae directions in the same way a sailing ship would do if it had to keep changing direction to get to shore. The first vector drawn for an element with known phase and current was drawn which happened to be a vertical line of known length. The next line was then added at the end to reflect the current and phase of the next element chosen and then onto the next element chosen. But this element presented a phase and current that was equal and opposite to the one previously drawn which meant that I was back to the tail end of my first vector chosen ! Thes two elements are termed destructive In fact this happened several times where vectors cancelled each other so we are just left with a singe vector in our scalar drawing .This meant to get back to the point of origin and remembering Newton's law previously alluded to the scalar drawing it represents a vector that is equal to the starting vector drawn, THE SAME PHASE and same CURRENT. Thus the polygon reflects an array where the phase is constant but the currents are ADDITIVE This represents the radiation pattern of a figure eight EXCEPT all the radiation is now to one side of the feed point and comprising of a single and larger circle. All of this reflects exactly what I stated below except I assumed that the pologon phase drawing was already known to all, for which I apologise. With NEC I constructed a model that closely followed this format though the real world did not make elements exactly equal but when I rehashed in my mind the basic priciples the polygon aproach verified that this aproach does give extraordinary front to back/rear figures that gave rise to mistrust of the softwear being used where you may remember that I commented on a model that I made and where the response was that the f/b was to high a point that had troubled me for many a month. Sorry for the long winded response which reflects what I have gone thru with my postings which apparently projected me as a total fool that gave rise to dirisive comments. Now I ask again, is there any written work that pertains to max gain and f to b/rear being on the same frequency? Best regards to all, no hard feelings Art KB9MZ................XG " wrote in message news:dySVd.30807$r55.174@attbi_s52... I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art |
Thank you for your polite response. Hopefully the written description of my
thought processes will satisfy a few tho not probably all Regards Art " wrote in message news:dySVd.30807$r55.174@attbi_s52... I have just come to realise that if one drew a polygon of element phases in a array and all elements were 180 degrees to its companion element and excluding the driven element, the max gain and max front to back will occur at the SAME frequency! Until now I was of the understanding that these two max figures could not occur at the same frequency. Is there anything written about this possibility? Regards Art |
Sorry, Art, but the reason I don't appreciate your ideas isn't because I
don't understand vectors or analysis from first principles or because I have some sort of prejudice against something in your background. It's simply that you're unable to communicate your ideas in a way I can understand them and, for all your many postings, I've yet to see any data that show you've done something extraordinary. I can only speak for myself, but suspect that some others might be in the same boat. Roy Lewallen, W7EL wrote: O.K..O..K Seems like everybody has forgotton the basics of the polygon of forces and other uses of vector so I will go over the basics. At the age of 14 yearsI entered the School of Engineering and Navigation where they hashed things from first principles, Since I had little schooling . . . |
Well we shall see Roy, but I find it hard to believe that you
with your antenna knoweledge plus being an engineer do not understand vectors. I can only believe that American education skirts this issue but then all of my engineering books including those by known antenna engineering gurus dwell upon it as well as authors in subjects such as classical electromechanical fields. Frankly, I see you as an expert in the field with long experience and as such feel that all is known about antennas and you cannot contemplate the idea that this is not so and you of all people missed the importance of what I stated. This is very much like the editing of a movie when it is found that the most interesting parts finished up on the cutting room floor as it was deemed insignificant. If what I state is confirmed then I will present it to the Radcom people since QST is now firmly in the hands of experts that believe all is known and has lost touch with the experimentor to which many of the ham fraternity still belong. I am aware that to some I am a poor communicator, but I went out of my way to clearly inform people on the subject of vectors and carefully tied the subject back to my original post such that those with a non science background can follow step by step the trend of thought of my original posting. Regards Art "Roy Lewallen" wrote in message ... Sorry, Art, but the reason I don't appreciate your ideas isn't because I don't understand vectors or analysis from first principles or because I have some sort of prejudice against something in your background. It's simply that you're unable to communicate your ideas in a way I can understand them and, for all your many postings, I've yet to see any data that show you've done something extraordinary. I can only speak for myself, but suspect that some others might be in the same boat. Roy Lewallen, W7EL wrote: O.K..O..K Seems like everybody has forgotton the basics of the polygon of forces and other uses of vector so I will go over the basics. At the age of 14 yearsI entered the School of Engineering and Navigation where they hashed things from first principles, Since I had little schooling . . . |
On Thu, 10 Mar 2005 20:30:15 GMT, "
wrote: Well we shall see Roy, but I find it hard to believe that you with your antenna knoweledge plus being an engineer do not understand vectors. This in response to Roy's post that states in part: "...but the reason I don't appreciate your ideas isn't because I don't understand vectors." [snip] I am aware that to some I am a poor communicator, Here is the problem, simply stated. but I went out of my way to clearly inform people on the subject of vectors and carefully tied the subject back to my original post such that those with a non science background can follow step by step the trend of thought of my original posting. We don't need a long convoluted pseudo treatise on vectors, give us some raw meat that simply states what it is that you're trying to/are doing. And, I have to ask since it is the subject, why is necessary or important to have max gain and F/B at the same frequency? |
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 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. 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 Regards Art...KB9MZ....XG "Wes Stewart" wrote in message ... On Thu, 10 Mar 2005 20:30:15 GMT, " wrote: Well we shall see Roy, but I find it hard to believe that you with your antenna knoweledge plus being an engineer do not understand vectors. This in response to Roy's post that states in part: "...but the reason I don't appreciate your ideas isn't because I don't understand vectors." [snip] I am aware that to some I am a poor communicator, Here is the problem, simply stated. but I went out of my way to clearly inform people on the subject of vectors and carefully tied the subject back to my original post such that those with a non science background can follow step by step the trend of thought of my original posting. We don't need a long convoluted pseudo treatise on vectors, give us some raw meat that simply states what it is that you're trying to/are doing. And, I have to ask since it is the subject, why is necessary or important to have max gain and F/B at the same frequency? |
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