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How can I measure or observe my hf antenna's take off angle?
Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about
antenna modeling but is there any way to do a real world take off angle measurement??? -- Charlie Ham Radio - AD5TH www.ad5th.com Live Blues Music www.492acousticblues.com |
"Charlie" wrote
Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there any way to do a real world take off angle measurement??? It will take a lot of thrust, that 5-BTV might require 2 propane tanks ;-) Be sure to disconnect the radials first! Sorry, couldn't resist that. Jack |
Charlie wrote:
Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there any way to do a real world take off angle measurement??? Sure, just rent a helicopter and make field strength measurements. -- 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 =--- |
wind a small RX i.e.: a field strength coil and LED indicator, or buy one of
them cheap 'bug detectors', stick on a gas filled WX balloon, get a hand held radio or mobile phone, and place a RX next to the radio Mic, put your radio on VOX and key from out side, by talking into the hand held, drag the balloon round with long a string observing the bug detector as a led field strength meter by viewing the LED barographs twinkling light, with a binocular. Easier at night. |
Thanks for all those helpful remarks..I have the LED ready along with the
balloon. I really liked the helicopter idea....you guys are so helpful!! LOL!!! -- Charlie Ham Radio - AD5TH www.ad5th.com Live Blues Music www.492acousticblues.com wrote in message ... wind a small RX i.e.: a field strength coil and LED indicator, or buy one of them cheap 'bug detectors', stick on a gas filled WX balloon, get a hand held radio or mobile phone, and place a RX next to the radio Mic, put your radio on VOX and key from out side, by talking into the hand held, drag the balloon round with long a string observing the bug detector as a led field strength meter by viewing the LED barographs twinkling light, with a binocular. Easier at night. |
Charlie............I read the posts with humor as well. Sounds
like you would like to do some serious field measurements. I will say that one year for field day two friends and myself put up a 4BTV, with 32 radials out. We got out so well with it we took the 40M dipole down. We worked quite a bit of DX as well, this was from a mountain top. I think too many people sell the verticles short...............and I will bow out at this point. 73, WB7FFI "Charlie" wrote in message ... Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there any way to do a real world take off angle measurement??? |
Charlie wrote:
"Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there a way to do a real world take off angle measurement?" Make a small physical model. Then use a field strength meter without a helicopter. Best regards, Richard Harrison, KB5WZI |
Hi John and thx for the reply. I too used to sell verticals short and I was
mystified why anyone would admit to having a "ground mounted" vertical of all kinds. But with a well built vertical and plenty of radials one can bust pileups in DX...I am so pleased with my 5-BTV. -- Charlie Ham Radio - AD5TH www.ad5th.com Live Blues Music www.492acousticblues.com "John Franklin" wrote in message ink.net... Charlie............I read the posts with humor as well. Sounds like you would like to do some serious field measurements. I will say that one year for field day two friends and myself put up a 4BTV, with 32 radials out. We got out so well with it we took the 40M dipole down. We worked quite a bit of DX as well, this was from a mountain top. I think too many people sell the verticles short...............and I will bow out at this point. 73, WB7FFI "Charlie" wrote in message ... Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there any way to do a real world take off angle measurement??? |
Hi Richard thx for the reply but in thinking it over it would seem an
unlikely possibility that I could accurately model the 5-BTV with it's traps. Did I miss something there? -- Charlie Ham Radio - AD5TH www.ad5th.com Live Blues Music www.492acousticblues.com "Richard Harrison" wrote in message ... Charlie wrote: "Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there a way to do a real world take off angle measurement?" Make a small physical model. Then use a field strength meter without a helicopter. Best regards, Richard Harrison, KB5WZI |
"Cecil Moore" Charlie wrote: Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there any way to do a real world take off angle measurement??? Sure, just rent a helicopter and make field strength measurements. ============================== What use would he make of take-off angle if he ever gets to know it. |
Reg Edwards wrote:
"Cecil Moore" Sure, just rent a helicopter and make field strength measurements. What use would he make of take-off angle if he ever gets to know it. Maybe it would make him feel good? Sorta like your Cabernet? :-) -- 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 =---- |
Charlie wrote: Hi Richard thx for the reply but in thinking it over it would seem an unlikely possibility that I could accurately model the 5-BTV with it's traps. Did I miss something there? Hi Charlie, A 5-BTV with 72 radials will have about the same take off angle as a full size vertical with 72 radials on a given band. This is assuming the 5-BTV is operated as a 1/4 wave, current fed vertical on all bands. If it is used as something else, say a 1/2 wave voltage fed vertical on a given band, then the TOA should be about the same as a full size 1/2 wave vertical. As you can tell by other posts, actually measuring the TOA will be difficult. If you could model full size versions of the 5-BTV on the bands of interest on a program such as Eznec, you could find out your TOA. As Reg asked, when you do find it out, what are you gonna do then? Gary N4AST |
Cecil Moore wrote:
Reg Edwards wrote: "Cecil Moore" Sure, just rent a helicopter and make field strength measurements. What use would he make of take-off angle if he ever gets to know it. Maybe it would make him feel good? Sorta like your Cabernet? :-) I want to measure the Cabernet of my antenna!!! - Mike KB3EIA - |
Reg
If he knew the TOA could he not ascertain the height of the reflecting layer using your "hop distance" program:. I suspect that your program on the same subject has a similar use so perhaps you could answer your own question. With my antenna having a TOA of 10 degrees I could work out backwards a whole mine of information all based around your program, assuming your input data is correct. Grin Cheers Art "Reg Edwards" wrote in message ... "Cecil Moore" Charlie wrote: Using a Hustler 5-BTV ground mounted with 72 radials. I have heard about antenna modeling but is there any way to do a real world take off angle measurement??? Sure, just rent a helicopter and make field strength measurements. ============================== What use would he make of take-off angle if he ever gets to know it. |
On Fri, 04 Mar 2005 05:24:23 GMT, "
wrote: With my antenna having a TOA of 10 degrees Hi Art, All antennas have a TOA of 10 degrees. That is possibly why Reggie (and others) generally advise that worshiping at the altar of TOA is illusory. Without some real data, like 0.2 dBi @ 10°, simply saying you have a TOA of 10 degrees is like trying to sell this wonderful car because it has brakes that work. 73's Richard Clark, KB7QHC |
TOA is deemed to be the angle at which maximum gain occurs.
Seems like you are fishing for something, but you will not get it from me. Art "Richard Clark" wrote in message ... On Fri, 04 Mar 2005 05:24:23 GMT, " wrote: With my antenna having a TOA of 10 degrees Hi Art, All antennas have a TOA of 10 degrees. That is possibly why Reggie (and others) generally advise that worshiping at the altar of TOA is illusory. Without some real data, like 0.2 dBi @ 10°, simply saying you have a TOA of 10 degrees is like trying to sell this wonderful car because it has brakes that work. 73's Richard Clark, KB7QHC |
wrote:
TOA is deemed to be the angle at which maximum gain occurs. Seems like you are fishing for something, but you will not get it from me. The problem seems to be that the definition of TOA is not standardized. Literally, TOA can be any angle but has a special meaning when quoting EZNEC. Neither my antenna books nor "The IEEE Dictionary" define TOA. I did a search for "take off angle" and "TOA" on my ARRL Antenna Book CD with zero results. -- 73, Cecil, 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 =---- |
Exactly.
After all there is some gain at 0 degrees, very small of course, but would anybody consider that as the TOA.? It appears that many consider TOA of little importance, but just consider a antenna with a single feed point such as a big yagi for 20m with say a 60 foot boom. Even with the high gain its TOA is in the region of 13 degrees where smaller boom antennas will be about 14 degrees. Now say we have another antenna with a single feed that has a TOA of 10 degrees with the same gain as the big yagi !. Which antenna will OPEN the band ? They do NOT open at the same time even tho they have the same gain so where Reg states that no amount of changing or shaking the antennas is going to make a scrap of difference to the" hop" distance is patently incorrect. As an aside losses in a signal is directly related to the number of hops that it takes one hop less to communicate means a louder signal. You can design a single feed antenna with a TOA of +/- 25 percent from the norm which makes a terrific distance to the "hop " distance, especially if the lower contour of the main lobe is below the competition, as the lobe will be noticable thinner with a low TOA. You can ,ofcourse, lower the take off angle by using multiple antenna feeds ie stacking but that is another matter of discussion. Regards Art "Cecil Moore" wrote in message ... wrote: TOA is deemed to be the angle at which maximum gain occurs. Seems like you are fishing for something, but you will not get it from me. The problem seems to be that the definition of TOA is not standardized. Literally, TOA can be any angle but has a special meaning when quoting EZNEC. Neither my antenna books nor "The IEEE Dictionary" define TOA. I did a search for "take off angle" and "TOA" on my ARRL Antenna Book CD with zero results. -- 73, Cecil, 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 =---- |
On Fri, 04 Mar 2005 17:19:26 GMT, "
wrote: Now say we have another antenna with a single feed that has a TOA of 10 degrees with the same gain as the big yagi !. Hi Art, Simply using EZNEC's freely available yagi design, I can come up with a 11.4 dBi figure at 10 degrees. Can you say we have another antenna with a single feed that has a TOA of 10 degrees with more gain that this? 73's Richard Clark, KB7QHC |
I don't think there would be a problem in beating that!
I would expect many could come up with one better than that at a feed point height of 1 wave length. Isn't the max gain theoretical obtainable just short of 16dbi ? Allow for 0.5 db max losses seems like 15.5 dbi is obtainable. ( using perfect flat terrain ofcourse with a 60 foot boom 'big' yagi) With all the experts that reside on this group plus a zillion of antenna reference books I expect many to come up with antennas better than that. Isn';t all now known about antennas and placed in print? (Grin) It just needs is a bit of research or an expert to share his knowledge with civility. Art "Richard Clark" wrote in message ... On Fri, 04 Mar 2005 17:19:26 GMT, " wrote: Now say we have another antenna with a single feed that has a TOA of 10 degrees with the same gain as the big yagi !. Hi Art, Simply using EZNEC's freely available yagi design, I can come up with a 11.4 dBi figure at 10 degrees. Can you say we have another antenna with a single feed that has a TOA of 10 degrees with more gain that this? 73's Richard Clark, KB7QHC |
wrote:
You can ,ofcourse, lower the take off angle by using multiple antenna feeds ie stacking but that is another matter of discussion. Art, if you really want perfect control of your TOA, get a satellite tracking system. :-) -- 73, Cecil, 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 =---- |
On Fri, 04 Mar 2005 18:33:41 GMT, "
wrote: I expect many to come up with antennas better than that. Hi Art, Thanx, I just needed you to confirm that you, in fact, did not have such a design. 73's Richard Clark, KB7QHC |
Judging by newsgroup postings, I'd say the most common meaning of
"takeoff angle" is "that elevation angle at which an antenna radiates". For this to have any meaning, it's necessary to assume that the antenna radiates at only one angle and no others. Since this is a false assumption, the term "takeoff angle" as used by most amateurs is meaningless. I've never seen the term in any non-amateur publication -- it seems to be in the same category as "capture area" and "S unit", creations which only amateurs seem to have a need for. As you say, it has a precise definition as used in EZNEC. The first versions of ELNEC, incidentally, didn't report "takeoff angle" because I thought it to be unnecessary to point out what anyone can see from a glance at the pattern, and felt that the term would be misunderstood and misused. Turns out I was right -- it's misunderstood and misused, despite my best effort at explicitly defining it. But you've gotta give the customer what he wants, not what he needs. Roy Lewallen, W7EL Cecil Moore wrote: wrote: TOA is deemed to be the angle at which maximum gain occurs. Seems like you are fishing for something, but you will not get it from me. The problem seems to be that the definition of TOA is not standardized. Literally, TOA can be any angle but has a special meaning when quoting EZNEC. Neither my antenna books nor "The IEEE Dictionary" define TOA. I did a search for "take off angle" and "TOA" on my ARRL Antenna Book CD with zero results. -- 73, Cecil, W5DXP |
Do you really think that I wasn't wise to the games you play ?
You was gearing up for an augument so I gave you nothing you could argue about. Check mate ! Art "Richard Clark" wrote in message ... On Fri, 04 Mar 2005 18:33:41 GMT, " wrote: I expect many to come up with antennas better than that. Hi Art, Thanx, I just needed you to confirm that you, in fact, did not have such a design. 73's Richard Clark, KB7QHC |
Don't professionals use the term? Seems like it shows up in pro computor
programs. Doesn't the Antenna handbook refer to TOA ? I do know they made a graph of incoming RF ray angles which amounts to the same thing. What is wrong with the common perception that it is the angle of maximum gain? If you were designing a 'point to point' antenna would you not look for the angle of maximum gain? If so what would you call that angle ? If you are refering to an antenna lobe pattern could you not invoke the +/- 3 db points as used in many other places in antenna work? Methinks that people are looking for problems to argue about Art "Roy Lewallen" wrote in message ... Judging by newsgroup postings, I'd say the most common meaning of "takeoff angle" is "that elevation angle at which an antenna radiates". For this to have any meaning, it's necessary to assume that the antenna radiates at only one angle and no others. Since this is a false assumption, the term "takeoff angle" as used by most amateurs is meaningless. I've never seen the term in any non-amateur publication -- it seems to be in the same category as "capture area" and "S unit", creations which only amateurs seem to have a need for. As you say, it has a precise definition as used in EZNEC. The first versions of ELNEC, incidentally, didn't report "takeoff angle" because I thought it to be unnecessary to point out what anyone can see from a glance at the pattern, and felt that the term would be misunderstood and misused. Turns out I was right -- it's misunderstood and misused, despite my best effort at explicitly defining it. But you've gotta give the customer what he wants, not what he needs. Roy Lewallen, W7EL Cecil Moore wrote: wrote: TOA is deemed to be the angle at which maximum gain occurs. Seems like you are fishing for something, but you will not get it from me. The problem seems to be that the definition of TOA is not standardized. Literally, TOA can be any angle but has a special meaning when quoting EZNEC. Neither my antenna books nor "The IEEE Dictionary" define TOA. I did a search for "take off angle" and "TOA" on my ARRL Antenna Book CD with zero results. -- 73, Cecil, W5DXP |
On Fri, 04 Mar 2005 20:42:10 GMT, "
wrote: Do you really think that I wasn't wise to the games you play ? You was gearing up for an augument so I gave you nothing you could argue about. Now THAT sounds like playing games, when I ask for a technical specification in a technical newsgroup. Check mate ! as does that. Hi Art, It remains extremely difficult to separate these obscure postings which defy distinction between your work and your fantasies, Art. This recent introduction of TOA appears to have been fantasy. 73's Richard Clark, KB7QHC |
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"Roy Lewallen" wrote in message ... wrote: Don't professionals use the term? I don't believe so. snip The ARRL Antenna Book probably uses TOA. It's a publication intended for amateurs. No, a graph of incoming ray angles is not a graph of TOA as used by EZNEC and other programs. You've just given a good example of the misunderstanding and confusion that the term is subject to. They give an incoming angle not a spread What is wrong with the common perception that it is the angle of maximum gain? Nothing at all. It's just that a lot of people think it means something else. In some of your postings, in fact, I get the sense that you don't always use it with that meaning. For example, you sometimes seem to give a lot of weight to the TOA as a figure of merit, and none at all to the hing field strength or gain at the angle at which communication is taking place. So either you're using TOA in a different sense, or you have no interest in maximizing the ability of an antenna to communicate effectively. snip Roy, by now you must know that I experiment a lot using computor models and actual building. I built a 80 meter boom yagi which was neat because the underside of the first lobe captured a lot of signals as the band is opening. So was the next step to make even a longer boom yagi to drive the underside of the lobe lower, no ....because I am now too old and weaker. So I now pursue the object of a lower take of angle by using more elements with more coupling and one that can rotate in a circle equivalent to a two element beam. I believe this can be accomplished with the same gain and a lower take off angle than a 60 foot boom yagi. Thus TOA becomes the most important thing for me as well as the "thickness" of the lobe. That is the sense that your response questioned regarding my maximisation of antenna performance for which I use TOA. Best regards Art |
"Cecil Moore" wrote The problem seems to be that the definition of TOA is not standardized. ======================= Cecil, it's worse than that. TOA is almost meaningless. Whoever coined the phrase "Take Off Angle" in conjunction with Eznec-type radiation patterns should be made to provide a 5000-word written explanation before he went to bed on his wedding night. Another form of safe sex? In the first place, your suggestion to hire a helicopter to fly around the sky in the vicinity of an antenna to determine the TOA would provide a completely different TOA from that provided by Eznec. Especially at low angles, say less than 30 degrees. That's because the angle at which radiation is strongest in the vicinity of a vertical antenna, of height 5/8-wavelength or shorter, is ALWAYS at an angle of ZERO degrees. ie., it is strongest along the ground surface regardless of soil conditions. Distance from the antenna is too short for the ground wave to be appreciably attenuated. Somehow or other, Eznec manages to calculate relative field strength at some great distance from the antenna. Which is, of course, an ultimate worthwhile but unobtainable objective. Unfortunately, Eznec ignores what that distance may be, whether the receiver is at ground level or at aircraft height, or in the stratosphere. In the extreme state of uncertainty it ignores the height of the ionospheric reflecting layer and the number of hops. In other words, if the location of the receiving antenna in space or time of day are unknown then the Eznec TOA is meaningless. So why is so much importance or significance attached to an Eznec TOA? It is merely one of the infinite number of angles contained in a very broad lobe of a radiation pattern. The path actually taken by a particular radio wave is of far greater importance. And knowing the location on the Earth's surface of both transmitting and receiving antennas, the path taken, including elevation angle, is calculable purely by geometric means. It has nothing to do with the antenna, not even a G5RV. If the ballpark Eznec TOA, by chance, happens to crudely coincide with the actual radio path angle to a distant receiver then that's the best which can be expected. If not, then there's nothing you can do about it except change the antenna, all the soil in your back yard, or your geograhical location. Save yourself the going-rate per hour of the fee for hiring a helicopter. ;o) By the way, this assessment of the situation in no way demeans the value and usefulness of Roy's Eznec - an excellent practical, educational and free-issue program. My only criticism is that it requres a 4-week course of self-instruction, two hours per day, to understand how to use it. But I suppose, starting from scratch, this is inevitable. I imagine that simply to point to Eznec in response to an elementary query on this newsgroup can often lead to a waste of time down-loading it, disappointment and frustration. ---- Reg, G4FGQ |
On Sat, 05 Mar 2005 14:34:11 GMT, "
wrote: Thus TOA becomes the most important thing for me as well as the "thickness" of the lobe. That is the sense that your response questioned regarding my maximisation of antenna performance for which I use TOA. Hi Art, Back when fractal antennas ruled the sky - at least on paper - the bragging rights were carefully tailored to fit the design. Some of this was arguably targeted to a user population that would have enjoyed the advantage. Anyway, such an example is shown at: http://www.qsl.net/kb7qhc/antenna/fr...r/k2/index.htm The fractal flyer, and its superior, simpler cousin the H Flyer showed a real, improved, DX response at 10 degrees. This was not their best response angle which you call TOA. In fact, both designers studiously ignored what you call TOA because it was not particularly notable. So, as a bald statement, both designs constitute very small antennas that exhibit BETTER gain figures at a TOA of 10 degrees than a full sized dipole held at a comparable height. Also, these antennas show a F/B that is very much better than a full sized antenna. Further, both designs, but notably the H Flyer, show full band matching. However, having said that, sans actual response levels or context, is having said nothing. However, let's look at the full characteristics, not simply the claims: Best Response: Std Dipole 0 dBi @ 90° fractal flyer -0.81 dBi @ 39° H Flyer -0.6 dBi @ 45° 10 Deg. Response: Std Dipole -7.51 dBi fractal flyer -4.85 dBi H Flyer -4.75 dBi 2:1 Match Range: Std Dipole 0.85 MHz fractal flyer 0.5 MHz H Flyer 1.0 MHz As can be seen, the H Flyer was the best design across the board, IF you accepted the limitations originally imposed (very low, very small, and scrutinized at 10 degree take off). Does this qualify it as a good antenna? Depends on if you are space and height limited. One last point, as poor as a valuation of -5dBi is, there are very few designs (barring the two shown here) that can perform better and still fit in the box. So, let's return to claims, especially for the H Flyer: Smallest resonant antenna; Highest DX Gain; Widest Bandwidth: Best F/B; Not a Fractal. 73's Richard Clark, KB7QHC |
An equation that I find useful when starting to think about a tradeoff
between antenna height of a horizontally polarized antenna and performance is: Beta-N = ArcSin(N * 74.948/H * F) N is an integer. H is the height of a horizontal antenna above a flat, perfectly reflecting surface in meters. F is the frequency of operation in MHz. Beta-N is in degrees. For N = 0, 2, 4, 6 ..., Beta-N is the angle above the horizon of a (theoretical) null. For N = 1, 3, 5 ..., Beta-N is the angle above the horizon of a maximum. I store this equation in my calculator and can solve for any of the variables. Thus: at 18 MHz, it takes a height of 32.2 meters to have the first null (above the horizon itself) at 15 degrees (N=2) - and, at the same height, the first peak (N=1) will be at 7.4 degrees. Of course, the earth is not flat and is not perfectly reflecting (even for horizontally polarized waves) and so on ... However, this equation helps with a first cut. [For those who use feet, the coefficient is 245.89 rather than 74.948.] 73, Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: |
I really do not understand what you are getting at.
Your antennas are very small but are outside my interests. I am looking for as long a hop that I can get on 20 meters and ofcourse it must accept power.Beyond a 80 foot boom I am constricted , thus I work backwards and start off with a smaller antenna to which I apply changes in design to obtain the equivalent of a 60 foot antenna based on the contour of the main lobe bottom. ( this includes changing the structure so that the gain and front to back maximises at the same frequency which is where the f/b is really meaningfull ) This is a long, long way from what you are describing and I might add that my antenna design must be multi banded when I have attained the 60 foot boom equivalency. Armed with this achievement I can now proceed to attacking the problem of exceeding the 60 foot boom yagi performance by using the now freed up land space Can you re phrase your posting, possibly from a different direction, exacty what you are trying to add to this thread especially where it affects what I have posted. Regards Art ard Clark" wrote in message ... On Sat, 05 Mar 2005 14:34:11 GMT, " wrote: Thus TOA becomes the most important thing for me as well as the "thickness" of the lobe. That is the sense that your response questioned regarding my maximisation of antenna performance for which I use TOA. Hi Art, Back when fractal antennas ruled the sky - at least on paper - the bragging rights were carefully tailored to fit the design. Some of this was arguably targeted to a user population that would have enjoyed the advantage. Anyway, such an example is shown at: http://www.qsl.net/kb7qhc/antenna/fr...r/k2/index.htm The fractal flyer, and its superior, simpler cousin the H Flyer showed a real, improved, DX response at 10 degrees. This was not their best response angle which you call TOA. In fact, both designers studiously ignored what you call TOA because it was not particularly notable. So, as a bald statement, both designs constitute very small antennas that exhibit BETTER gain figures at a TOA of 10 degrees than a full sized dipole held at a comparable height. Also, these antennas show a F/B that is very much better than a full sized antenna. Further, both designs, but notably the H Flyer, show full band matching. However, having said that, sans actual response levels or context, is having said nothing. However, let's look at the full characteristics, not simply the claims: Best Response: Std Dipole 0 dBi @ 90° fractal flyer -0.81 dBi @ 39° H Flyer -0.6 dBi @ 45° 10 Deg. Response: Std Dipole -7.51 dBi fractal flyer -4.85 dBi H Flyer -4.75 dBi 2:1 Match Range: Std Dipole 0.85 MHz fractal flyer 0.5 MHz H Flyer 1.0 MHz As can be seen, the H Flyer was the best design across the board, IF you accepted the limitations originally imposed (very low, very small, and scrutinized at 10 degree take off). Does this qualify it as a good antenna? Depends on if you are space and height limited. One last point, as poor as a valuation of -5dBi is, there are very few designs (barring the two shown here) that can perform better and still fit in the box. So, let's return to claims, especially for the H Flyer: Smallest resonant antenna; Highest DX Gain; Widest Bandwidth: Best F/B; Not a Fractal. 73's Richard Clark, KB7QHC |
On Sun, 06 Mar 2005 04:25:06 GMT, "
wrote: Can you re phrase your posting, possibly from a different direction, exacty what you are trying to add to this thread especially where it affects what I have posted. = both designs exhibit BETTER gain figures at a TOA of 10 degrees than a full sized dipole held at a comparable height. However, having said that, sans actual response levels or context, is having said nothing. If you neglect giving us response levels, or context (like height, length, frequency, ground conditions) then telling us you have a great 10 degree TOA is meaningless. More to the matter of the thread, it you cannot tell us antenna location and that location of the intended DX, and the height of the skip layer, then a great 10 degree TOA could easily be useless. If this is simply about bragging rights that knowing the DX location is inconsequential because you will hit somebody, that could as easily be said about a great 20 degree TOA antenna which makes the great 10 degree TOA antenna another face in the crowd. 73's Richard Clark, KB7QHC |
Beta-N = ArcSin(N * 74.948/H * F)
The equation is not doubted. Could somebody please check that Eznec nulls at N=2 and N=4 agree with it above a perfect ground. ---- Reg, G4FGQ |
"J. Mc Laughlin" wrote Beta-N = ArcSin(N * 74.948/H * F) ========================= Mac, you are of the same heart as myself. If you have an equation simple enough to write here which computes the relative magnitudes of the maximums, could you please oblige? I could write a program which incorporates it. ---- Reg, G4FGQ |
"J. Mc Laughlin" wrote Beta-N = ArcSin(N * 74.948/H * F) ========================= There are two typing errors in the above equation. Beta-N does not mean Beta minus N. It just means the N'th value of Beta. And the intended equation should be - Beta = ArcSin(74.948*N/H/F) degrees. Alternatively, Sin(Beta) = 74.948*N/H/F degrees. That is, divide by F, NOT multiply by F. ---- Reg, G4FGQ |
Now I understand where you are coming from !.
I've given a lot of info out about the antenna and its attributes, many of which are unique. Also why I am following this path I do not consider these posts mention of the attributes such as feed point height or details regarding F/B as meaningless and certainly not points about which to argue. I did ask on another posting if there was anything written on a particular subject regarding a particular feature but there was no response so there is not a lot of interest in some aspects If I have declared something that is impossible I would be happy to debate it but at this point I am not ready to publish all details which I am sure that you understand Art "Richard Clark" wrote in message ... On Sun, 06 Mar 2005 04:25:06 GMT, " wrote: Can you re phrase your posting, possibly from a different direction, exacty what you are trying to add to this thread especially where it affects what I have posted. = both designs exhibit BETTER gain figures at a TOA of 10 degrees than a full sized dipole held at a comparable height. However, having said that, sans actual response levels or context, is having said nothing. If you neglect giving us response levels, or context (like height, length, frequency, ground conditions) then telling us you have a great 10 degree TOA is meaningless. More to the matter of the thread, it you cannot tell us antenna location and that location of the intended DX, and the height of the skip layer, then a great 10 degree TOA could easily be useless. If this is simply about bragging rights that knowing the DX location is inconsequential because you will hit somebody, that could as easily be said about a great 20 degree TOA antenna which makes the great 10 degree TOA antenna another face in the crowd. 73's Richard Clark, KB7QHC |
Providing actual values should have resolved any latent ambiguity.
Nevertheless, I should have assumed the use of a TI calculator. Beta-sub-N = ArcSin( (N * 74.948)/(H * F)) The argument of the ArcSin is the product of N times the indicated coefficient all divided by the product of the height times the frequency. Height is in meters. Frequency is in MHz. N is an integer. Even values of N apply to nulls. Odd values of N apply to peaks. Beta-sub-N is an angle in degrees measured from the horizon towards the zenith. The equation assumes an isotropic*, purely horizontally polarized antenna; and a ground that is flat and has a reflection coefficient of minus-one for an incident horizontally polarized wave independent of the angle-of-incidence. * Note: In this context, isotropic is to be understood to mean broadside gain is constant and is independent of angle. Fortunately, broadside to most horizontally antennas and for most grounds, the conditions are close to being satisfied for Beta up to perhaps 30 degrees. The angles that are important for "DX," I have found to be between two and twelve degrees. In other words, if long distance contacts are desired, it is desirable to have most of an antenna's gain be between 2 and 12 degrees above the horizon. Consider the person who places a 14.2 MHz Yagi at 60 meters (the magic height above which one has to deal with the FAA). As a first approximation, such an antenna is expected to have a peak at about 5 degrees and a null at about 10 degrees. When the band opens, such a system is likely to dominate. When propagation is better, those with lower antennas might have more gain at the useful angle. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Reg Edwards" wrote in message ... "J. Mc Laughlin" wrote Beta-N = ArcSin(N * 74.948/H * F) ========================= There are two typing errors in the above equation. Beta-N does not mean Beta minus N. It just means the N'th value of Beta. And the intended equation should be - Beta = ArcSin(74.948*N/H/F) degrees. Alternatively, Sin(Beta) = 74.948*N/H/F degrees. That is, divide by F, NOT multiply by F. ---- Reg, G4FGQ |
"J. Mc Laughlin" wrote in message ... snip .. The angles that are important for "DX," I have found to be between two and twelve degrees. In other words, if long distance contacts are desired, it is desirable to have most of an antenna's gain be between 2 and 12 degrees above the horizon. At last reason prevails....... For DX purposes only the bottom half of the main lobe is usefull. If your TOA is 13 to 14 degrees which is average then more than 50 percent of the main lobe is serving no purpose. If one wants to capture the highest possible number of DX contacts then the TOA should be the angle where the upper side of the main lobe is 3db down from the TOA. Lower than this point renders the antenna useless as propagation sets in. Mac shows this with a antenna having a TOA at 5 degrees that has a theoretical NULL at 10 degrees which means 50 percent of incoming signals are not available to the antenna user Consider the person who places a 14.2 MHz Yagi at 60 meters (the magic height above which one has to deal with the FAA). As a first approximation, such an antenna is expected to have a peak at about 5 degrees and a null at about 10 degrees. When the band opens, such a system is likely to dominate. When propagation is better, those with lower antennas might have more gain at the useful angle. 73 Mac N8TT -- Reg, G4FGQ Regards Art |
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