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6M stacked loops - best height above ground?
Currently the top loop is at only 20ft but I am making many contacts. Soon
however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... -- Charlie-AD5TH |
6M stacked loops - best height above ground?
On Tue, 27 Dec 2005 10:52:54 -0600, "Charlie"
wrote: Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... You really want the lower of the two higher than 20ft. It's really simple, higher is better. We are talking VHF and if there is nothing going on propagation wise then height above average terrain determines what your radio horizon will be. For that higher wins. Simply put, 80ft will be much better than 20 and only slightly better than 40. Allison |
6M stacked loops - best height above ground?
ORIGINAL MESSAGE: On Tue, 27 Dec 2005 10:52:54 -0600, "Charlie" wrote: Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I'm not that sure about loops, but for yagis working DX, the optimum height seems to be about 35 feet. Higher is better for ground wave, but for DX, 35 is best, believe it or not. This has been proven with crank up towers many times. It may well be the same for loops. 73, Bill W6WRT |
6M stacked loops - best height above ground?
"Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... 6m is line-of-sight, so higher is better than lower. If you have the opportunity to put it 80 ft high - do it. why are you stacking loops? why not make a quad ? |
6M stacked loops - best height above ground?
Thank you Allison.....
-- Charlie wrote in message ... On Tue, 27 Dec 2005 10:52:54 -0600, "Charlie" wrote: Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... You really want the lower of the two higher than 20ft. It's really simple, higher is better. We are talking VHF and if there is nothing going on propagation wise then height above average terrain determines what your radio horizon will be. For that higher wins. Simply put, 80ft will be much better than 20 and only slightly better than 40. Allison |
6M stacked loops - best height above ground?
Hi Bill...this is also what I have found to be the crux of my dilemma. If I
should strive to optimize height for DX or terrestrial contacts. I have need for both so I am going to need to compromise a bit. TY again for your input. -- Charlie "Bill Turner" wrote in message ... ORIGINAL MESSAGE: On Tue, 27 Dec 2005 10:52:54 -0600, "Charlie" wrote: Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I'm not that sure about loops, but for yagis working DX, the optimum height seems to be about 35 feet. Higher is better for ground wave, but for DX, 35 is best, believe it or not. This has been proven with crank up towers many times. It may well be the same for loops. 73, Bill W6WRT |
6M stacked loops - best height above ground?
Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... Charlie, Try asking these guys. WWW.uksmg.org 73's De Dave M1BTI -- Amateur Radio Call Sign M1BTI, Located in Manchester England. Locator square IO83TK Chairman Of Trafford Radio Club. Club Call Signs G0TRG & M1BBP Located at Umist, University Of Manchester Institute For Science And Technology Share What You Know, Learn What You Dont. |
6M stacked loops - best height above ground?
On Wed, 28 Dec 2005 02:33:45 -0500, "Hal Rosser"
wrote: "Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... 6m is line-of-sight, so higher is better than lower. If you have the opportunity to put it 80 ft high - do it. why are you stacking loops? why not make a quad ? I can answer for him. Stacked loops offer some amount of gain but are omnidirectional. A 2 element quad, offers slightly more gain but is directional. If both are on the SIDE of a tower, one has to be turned and is expensive to do that. Actually a single loop has better high angle when mounted high up than a stacked pair. After trying a lot of 6m antennas. Quads with wires thinner than 1/4" are only ok but doo poorly with ice and high wind. I'd do a yagi of 4 or more elements for gain and F/B and a loop up high for local nets(omni). Allison |
6M stacked loops - best height above ground?
Hi Charlie
I have read some of the responses you have received already. As you asked for first hand experience I hadnt commented initially. I wonder if you have tried modelling your configuration with height variables and applying the resultant radiation pattern to propagation modes? I'd suggest ground conditions for your area also need to be entered. I seem to remember from my dim dark past that ground reflections (and hence undesirable skyward radiation - often not usually an issue on VHF) are more of a problem when using a lower gain antenna. Maybe the loop in that respect might be worse than a quad/yagi? You'd be able to see the dB per foot height changes that occur and make a judgement from that. I have never used horiz loops on 6m. Cheers Bob W5/VK2YQA East Texas Charlie wrote: I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... |
6M stacked loops - best height above ground?
On Wed, 28 Dec 2005 02:33:45 -0500, Hal Rosser wrote:
"Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... 6m is line-of-sight, so higher is better than lower. IT IS??? !!! Then, I guess my confirmed QSO's with Japan, Australia, Greenland, Chile, and others -- plus all states except R.I. (sigh...) from western Colorado (while running just 9.5 watts) simply never happened. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK |
6M stacked loops - best height above ground?
On 28 Dec 2005 17:00:28 GMT, Allodoxaphobia
wrote: On Wed, 28 Dec 2005 02:33:45 -0500, Hal Rosser wrote: "Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... 6m is line-of-sight, so higher is better than lower. IT IS??? !!! Then, I guess my confirmed QSO's with Japan, Australia, Greenland, Chile, and others -- plus all states except R.I. (sigh...) from western Colorado (while running just 9.5 watts) simply never happened. Jonesy It is if the propagation isn't there or the moon is not a good shot. ;) Then again I only have 14 countries on under 20W in the last 3 years. I need KH and Alaska for WAS. RI is next door for me being in MA. Even with the off peak years there is a lot of propagation that pops up at odd times. Allison |
6M stacked loops - best height above ground?
On Wed, 28 Dec 2005 08:25:18 -0600, Bob Bob wrote:
Hi Charlie I have read some of the responses you have received already. As you asked for first hand experience I hadnt commented initially. I wonder if you have tried modelling your configuration with height variables and applying the resultant radiation pattern to propagation modes? I'd suggest ground conditions for your area also need to be entered. I seem to remember from my dim dark past that ground reflections (and hence undesirable skyward radiation - often not usually an issue on VHF) are more of a problem when using a lower gain antenna. Maybe the loop in that respect might be worse than a quad/yagi? You'd be able to see the dB per foot height changes that occur and make a judgement from that. Real simple. He's so close to the ground he has a lot of high angle gain. As he goes up that will go down and the low angle gain will improve. I have never used horiz loops on 6m. Handy for local stuff like a 100 ore more miles in all directions. I use one for the listening as I miss stuff with beams. Allison |
6M stacked loops - best height above ground?
"Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... -- Charlie-AD5TH First off, what do you mean by LOOP? A Halo kind of antenna, or a vertically mounted loop? I suspect you mean a Halo (or M2). I ran an EZNEC simulation on a stacked pair, and it was not great. Minimum stacking distance is a bout 13 feet, with a gain 2db less than a single 3 element beam. Get the bugger up to 80 feet. A friend of mine had bought 2 M2 loops. Never bothered to put up the second one when he realized that you can't just stack them 3 feet apart. Remember, 20 feet is already a wavelength up. If you really want high angle radiation, it would have to be a lot lower than that. That will work for E skip, not very good for F2, or locals. Even at 80 feet, you will still have multiple lobes, with a good part of the energy going almost straight up. Tam/WB2TT |
6M stacked loops - best height above ground?
"Allodoxaphobia" wrote in message ... On Wed, 28 Dec 2005 02:33:45 -0500, Hal Rosser wrote: "Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... 6m is line-of-sight, so higher is better than lower. IT IS??? !!! Then, I guess my confirmed QSO's with Japan, Australia, Greenland, Chile, and others -- plus all states except R.I. (sigh...) from western Colorado (while running just 9.5 watts) simply never happened. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK OOPS! - sorry, I forgot about 50M DX - skip does happen at 50mhz sometimes I hear its an enjoyable pass-time to attempt long-distance short-duration contacts on 50mhz. Does ducting also occur on 50 ? |
6M stacked loops - best height above ground?
On Wed, 28 Dec 2005 17:34:33 -0500, Hal Rosser wrote:
"Allodoxaphobia" wrote in message ... On Wed, 28 Dec 2005 02:33:45 -0500, Hal Rosser wrote: "Charlie" wrote in message ... Currently the top loop is at only 20ft but I am making many contacts. Soon however they will be placed off a sidearm on the tower. The top loop could then be as high as 80 ft. I have read and read about this topic. Does anyone have any first hand knowledge of 6M height above ground comparisons especially for stacked loops? Thanks.... 6m is line-of-sight, so higher is better than lower. IT IS??? !!! Then, I guess my confirmed QSO's with Japan, Australia, Greenland, Chile, and others -- plus all states except R.I. (sigh...) from western Colorado (while running just 9.5 watts) simply never happened. OOPS! - sorry, I forgot about 50M DX - skip does happen at 50mhz sometimes Propagation to Japan, Australia, Greenland, Chile... ain't skip. It's F2 -- or Es-connected F2. Gets Real Crazy every 11 years or so. Does ducting also occur on 50 ? There's little that doesn't occur on 50 MHz. I have completed QSO's by Es, F2, Au, meteor, tropo ducting, and weird flavors and combinations of more than one of'em. Fellers also do EME on 6M - tho' not I. When the band is wide open on an Es opening -- maybe a 2X Es event -- you'll find the FB-OP-to-Jerk ratio Real High. It's one of the reasons I've all but given up on the 'popular' HF bands. And, to steer it back On Topic: Fiddl'in with antennas on 6M is SO EASY. 73 Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK |
6M stacked loops - best height above ground?
Propagation to Japan, Australia, Greenland, Chile... ain't skip. It's F2 -- or Es-connected F2. Gets Real Crazy every 11 years or so. Worked GB from MA only 2 years ago well off the solar peak. During the summer (2005) I got a few Carib stations and Brermuda. Does ducting also occur on 50 ? There's little that doesn't occur on 50 MHz. I have completed QSO's by Es, F2, Au, meteor, tropo ducting, and weird flavors and combinations of more than one of'em. Fellers also do EME on 6M - tho' not I. A local does the EME thing. I do low power (20W PEP max) off solar power. But I like the band as it's easy for antennas and fun to design radios for. When the band is wide open on an Es opening -- maybe a 2X Es event -- you'll find the FB-OP-to-Jerk ratio Real High. It's one of the reasons I've all but given up on the 'popular' HF bands. There have been times when it's like a 20m pileup. And, to steer it back On Topic: Fiddl'in with antennas on 6M is SO EASY. ;) Allison KB!GMX FN42HH |
6M stacked loops - best height above ground?
And to complicate matters further the max antenna height being talked
about being around 3-4 wavelengths off the ground is going to break the radiation pattern up into a number of lobes at various vertical angles. For that reason alone I think it is still worth modelling. There will be specific heights where the horizontal radiated component is at a maximum and this is likely the most desirable. It will also give a good indication of what takeoff angles will be like for ionospheric propagation modes. You'd also see the spacing/height effect on undesirable straight upwards radiation. Then again a crank up/down tower and maybe inter element spacing adjustment mght be a good empirical way to get the right data as well. Bob VK2YQA wrote: Real simple. He's so close to the ground he has a lot of high angle gain. As he goes up that will go down and the low angle gain will improve. |
6M stacked loops - best height above ground?
How is that you have your Forte Free Agent set up that you do not do
attributions? On Thu, 29 Dec 2005 12:47:41 GMT, wrote: When the band is wide open on an Es opening -- maybe a 2X Es event -- you'll find the FB-OP-to-Jerk ratio Real High. It's one of the reasons I've all but given up on the 'popular' HF bands. There have been times when it's like a 20m pileup. Ya, but... For the Greater Part, _everybody_ acts like Ladies And Gentlemen. You don't see that on 20M. Jonesy W3DHJ |
6M stacked loops - best height above ground?
Bob Bob wrote:
And to complicate matters further the max antenna height being talked about being around 3-4 wavelengths off the ground is going to break the radiation pattern up into a number of lobes at various vertical angles. For that reason alone I think it is still worth modelling. There will be specific heights where the horizontal radiated component is at a maximum and this is likely the most desirable. . . Modeling will show that at great distances from the antenna, the horizontally radiated field is zero from any horizontally polarized antenna over ground. Roy Lewallen, W7EL |
6M stacked loops - best height above ground?
On 29 Dec 2005 15:48:27 GMT, Allodoxaphobia
wrote: A fair amount of stuff turned off and.. Delete key. ;) Allison |
6M stacked loops - best height above ground?
On Thu, 29 Dec 2005 09:53:21 -0800, Roy Lewallen
wrote: Bob Bob wrote: And to complicate matters further the max antenna height being talked about being around 3-4 wavelengths off the ground is going to break the radiation pattern up into a number of lobes at various vertical angles. For that reason alone I think it is still worth modelling. There will be specific heights where the horizontal radiated component is at a maximum and this is likely the most desirable. . . Modeling will show that at great distances from the antenna, the horizontally radiated field is zero from any horizontally polarized antenna over ground. Roy Lewallen, W7EL Please see http://www.cebik.com/vhf/ex6.html on the topic. Near the end of the article he gets into the horizonatally polarized less than 1WL interrupted loops typical of 6m (halos, squares and triangles). For more, he also has an article on HOHPLs (horizontally oriented horizontally polarized loops 1WL and greater). Worth reading and observing the models used. Allison Kb1GMX FN42HH |
6M stacked loops - best height above ground?
True Roy
I should have said something like "approaches" the horizontal Apologies for the mis-speak I am also going to have to look into the theory of how much VHF diffracts and bends so one can choose the right angles grin.. Cheers Bob Roy Lewallen wrote: Modeling will show that at great distances from the antenna, the horizontally radiated field is zero from any horizontally polarized antenna over ground. Roy Lewallen, W7EL |
6M stacked loops - best height above ground?
Modeling will show that at great distances from the antenna, the
horizontally radiated field is zero from any horizontally polarized antenna over ground. Roy Lewallen, W7EL "Bob Bob" wrote True Roy. I should have said something like "approaches" the horizontal. Apologies for the mis-speak. ___________ Pending some clarification from one of you (or anyone else) as to what is meant here, I point out that h-pol radiation directed toward an elevation at/near ground level has been, and still is the basis for very successful commercial broadcasting by FM and TV stations. RF |
6M stacked loops - best height above ground?
Roy Lewallen wrote:
Modeling will show that at great distances from the antenna, the horizontally radiated field is zero from any horizontally polarized antenna over ground. I need to clarify this. It's based on a theoretical model which doesn't apply in many practical cases. It assumes that the signal reaches the destination by two paths, direct and via reflection from the ground; that the ground is perfectly flat at the point of reflection; and the destination is very far from the source. The lower the elevation angle being observed, the farther the destination has to be for this effect to occur. For example, consider the field strength at an elevation angle of one degree from an FM transmitter whose antenna is 1000 feet above the average terrain. Neglecting Earth curvature (which probably shouldn't be neglected in this case), at a very distant point, the reflected signal which will interfere with the direct signal strikes the ground at a point about 11 miles from the transmitter. The receiver would have to be more than 22 miles away (and of course, higher in elevation than the transmitting antenna) for reasonable cancellation to occur. At a half degree elevation angle, the receiver would have to be twice that distance; at a quarter degree, four times, and so forth. Full cancellation at zero elevation angle would occur only at an infinite distance. In many practical situations, you can safely assume that the potentially interfering ground reflection takes place beyond the receiver, so a better estimation of received signal strength can be obtained by looking at the free space pattern. Roy Lewallen, W7EL |
6M stacked loops - best height above ground?
Roy, I prefer my radiation patterns to be functions of the antenna itself. After all, that's what it's all about. To determine the field strength at a distance I prefer not to take any notice of Eznec's misleading ideas on the state of the ionosphere or groundwave loss and do my own calculations. Or I can follow up Eznec by using a program dedicated to either groundwave or ionospheric propagation. I agree preferences will differ. But it is important to understand exactly what radiation patterns do or do not mean. Please do not take this note as any criticism of Eznec. It is a valuable (and free) calculating resource. But, as you demonstrate, it is difficult to describe in a few words exactly what it does. Please simplify! ---- Reg. |
6M stacked loops - best height above ground?
Reg Edwards wrote:
Roy, I prefer my radiation patterns to be functions of the antenna itself. After all, that's what it's all about. That's just fine. All antenna modeling programs I know of allow selection of a free space environment, which gives you just what you want. To determine the field strength at a distance I prefer not to take any notice of Eznec's misleading ideas on the state of the ionosphere EZNEC makes no assumptions about the state of the ionosphere, or even its existence. or groundwave loss and do my own calculations. The only assumption EZNEC makes in its far field analysis about ground wave loss is that at an infinite distance it's infinite. The professional EZNEC programs, which do directly report far field ground wave signal strength when requested, use the Norton approximations (implemented in NEC) which are widely accepted. Or I can follow up Eznec by using a program dedicated to either groundwave or ionospheric propagation. I agree preferences will differ. But it is important to understand exactly what radiation patterns do or do not mean. With that I agree wholeheartedly. Please do not take this note as any criticism of Eznec. It is a valuable (and free) calculating resource. But, as you demonstrate, it is difficult to describe in a few words exactly what it does. Please simplify! First a note, EZNEC is not free. It's copyrighted, commercial software. Only the EZNEC demo program is free and can be copied and distributed freely. Like other powerful tools, EZNEC requires some effort on the part of the user to understand its use. If you're not willing to make that effort, I suggest that you not use it, but find (or write) a program that suits you and your limited willingness to learn. [Give NEC-2 or MININEC a try!] All types of EZNEC, including the demo program, include a comprehensive and extensively indexed manual. I also recommend the ARRL antenna modeling course, which numerous users have made positive comments about. But both of those are useful only to people who want more than to get a quick answer without taking any time to consider what the answer means. I'll leave it to you and others to produce simple programs which do one specific, simple thing. There's a place for those, but also a place for more versatile programs like EZNEC which unavoidably require a bit more effort to fully use. Roy Lewallen, W7EL |
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