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Verticals versus Horizontal Dipoles
There is much discussion about the relative merits of the simple
vertical versus horizontal dipole antennas. Their radiation patterns are well known. They are very broad in both the vertical and horizontal planes. Both have have a null. We need consider only the broadside, maximum, radiation from a dipole. Most of the arguments can be settled by considering the elevation angle of the path taken by the radio wave between the transmitting and receiving stations. Followed by a little elementary geometry or trigonometry. For present purposes a flat Earth can be assumed. At an elevation angle of around 45 degrees the strength of radiation received from vertical and horizontal antennas are about equal. (This has nothing to do with Eznec take-off angles.) The heights of the Ionospheric reflecting layers are - E-layer = 70 miles, daylight only. F1-layer = 140 miles, occasionally, in daylight only. F2-layer = 190 miles, night-time. F2-layer = 250 miles, in daylight. From flat-Earth geometry, at an elevation angle of 45 degrees, the distance between transmitting and receiving stations is twice the height of the reflecting layer. Therefore, at this distance the received signal strength can be expected to be about the same from both types of antenna. As the elevation angle decreases, the distance increases and radiation from the vertical antenna increases. The radiation from the dipole decreases. There is an extra propagation loss due to an increase in radio path length but this equally affects radiation from both antenna types. As the elevation angle increases towards the vertical, distance decreases, radiation from the dipole increases and radiation from the vertical antenna decreases in strength. The radio path loss decreases but the difference in pattern between the two antenna types is maintained at the receiver. With a spherical Earth, in daylight, using the F2-layer, at elevation angles around 5 degrees, one-hop distances of 3,500 miles can occur. With two hops, at angles of around 12 degrees, distances of 5,000 miles can occur. For each additional hop there is loss in the layer and loss in the reflection in the ground. Some parts of the radio path may be in daylight and others in darkness. More than one layer may be involved. Muli-path distortion occurs. Peculiar things happen and much depends on frequency. The low-angle performance of a half-wave dipole, even when radiating broadside towards the receiver, is very poor in comparison with a simple vertical. On the other hand, a simple vertical does reasonably well when working just across county because of the short propagation path, almost straight up and down again, or even via the groundwave for very short distances. ---- Reg, G4FGQ. |
Verticals versus Horizontal Dipoles
This rather oversimplified analysis overlooks an important factor. The
field radiated upward from an antenna seen at long distances (that is, the sky wave as contrasted to the short-range surface wave) consists of a vector sum of two components: one radiated directly, and one which is inintially radiated downward then reflected from the ground. The ground reflection alters both the magnitude and phase of the reflected component depending on ground characteristics and the polarization of the wave. At low angles, horizontally polarized waves are reflected very well even when the ground is quite poor; vertically polarized waves react differently. The resulting fields can fairly easily be calculated manually if desired using simple geometry, equations for reflection coefficient which can be found in Kraus and other references, and vector addition. One thing you'll quickly discover is that the field from a vertical does NOT monotonically increase as the elevation angle decreases, but decreases below a moderate angle determined by the ground characteristics. EZNEC (including the free demo) and other modeling programs clearly show this important effect. Roy Lewallen, W7EL Reg Edwards wrote: There is much discussion about the relative merits of the simple vertical versus horizontal dipole antennas. Their radiation patterns are well known. They are very broad in both the vertical and horizontal planes. Both have have a null. We need consider only the broadside, maximum, radiation from a dipole. Most of the arguments can be settled by considering the elevation angle of the path taken by the radio wave between the transmitting and receiving stations. Followed by a little elementary geometry or trigonometry. For present purposes a flat Earth can be assumed. At an elevation angle of around 45 degrees the strength of radiation received from vertical and horizontal antennas are about equal. (This has nothing to do with Eznec take-off angles.) The heights of the Ionospheric reflecting layers are - E-layer = 70 miles, daylight only. F1-layer = 140 miles, occasionally, in daylight only. F2-layer = 190 miles, night-time. F2-layer = 250 miles, in daylight. From flat-Earth geometry, at an elevation angle of 45 degrees, the distance between transmitting and receiving stations is twice the height of the reflecting layer. Therefore, at this distance the received signal strength can be expected to be about the same from both types of antenna. As the elevation angle decreases, the distance increases and radiation from the vertical antenna increases. The radiation from the dipole decreases. There is an extra propagation loss due to an increase in radio path length but this equally affects radiation from both antenna types. As the elevation angle increases towards the vertical, distance decreases, radiation from the dipole increases and radiation from the vertical antenna decreases in strength. The radio path loss decreases but the difference in pattern between the two antenna types is maintained at the receiver. With a spherical Earth, in daylight, using the F2-layer, at elevation angles around 5 degrees, one-hop distances of 3,500 miles can occur. With two hops, at angles of around 12 degrees, distances of 5,000 miles can occur. For each additional hop there is loss in the layer and loss in the reflection in the ground. Some parts of the radio path may be in daylight and others in darkness. More than one layer may be involved. Muli-path distortion occurs. Peculiar things happen and much depends on frequency. The low-angle performance of a half-wave dipole, even when radiating broadside towards the receiver, is very poor in comparison with a simple vertical. On the other hand, a simple vertical does reasonably well when working just across county because of the short propagation path, almost straight up and down again, or even via the groundwave for very short distances. ---- Reg, G4FGQ. |
Verticals versus Horizontal Dipoles
Reg:
Your simplistic analysis disagrees with my 50 years of operating local contacts on 75 meters here in the southern US. Practical verticals are universally 10 or more dB poorer than dipoles for local contacts, no matter what the other variables. The very best quarter wave 66 foot vertical with 365 radials is about equivalent to a dipole lying on the ground for 0 to 250 mile contacts on 75. Forty meters performs a little closer to your argument, but not much. Among long time local ragchewers, verticals are considered to radiate equally poorly in all directions. The NVIS nonsense also enters here. I have thrown back at the "proponents" of NVIS that elevation angles of 45 degrees or less hardly qualify as NVIS (properly NHIS, maybe?) but they continue to misuse common English to further their specious arguments. By the way, how much of the UK is within 500 miles of your QTH? I have to exceed 500 miles just to get out of the state of Texas. -- Crazy George W5VPQ My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap. "Reg Edwards" wrote in message ... There is much discussion about the relative merits of the simple vertical versus horizontal dipole antennas. Their radiation patterns are well known. They are very broad in both the vertical and horizontal planes. Both have have a null. We need consider only the broadside, maximum, radiation from a dipole. Most of the arguments can be settled by considering the elevation angle of the path taken by the radio wave between the transmitting and receiving stations. Followed by a little elementary geometry or trigonometry. For present purposes a flat Earth can be assumed. At an elevation angle of around 45 degrees the strength of radiation received from vertical and horizontal antennas are about equal. (This has nothing to do with Eznec take-off angles.) The heights of the Ionospheric reflecting layers are - E-layer = 70 miles, daylight only. F1-layer = 140 miles, occasionally, in daylight only. F2-layer = 190 miles, night-time. F2-layer = 250 miles, in daylight. From flat-Earth geometry, at an elevation angle of 45 degrees, the distance between transmitting and receiving stations is twice the height of the reflecting layer. Therefore, at this distance the received signal strength can be expected to be about the same from both types of antenna. As the elevation angle decreases, the distance increases and radiation from the vertical antenna increases. The radiation from the dipole decreases. There is an extra propagation loss due to an increase in radio path length but this equally affects radiation from both antenna types. As the elevation angle increases towards the vertical, distance decreases, radiation from the dipole increases and radiation from the vertical antenna decreases in strength. The radio path loss decreases but the difference in pattern between the two antenna types is maintained at the receiver. With a spherical Earth, in daylight, using the F2-layer, at elevation angles around 5 degrees, one-hop distances of 3,500 miles can occur. With two hops, at angles of around 12 degrees, distances of 5,000 miles can occur. For each additional hop there is loss in the layer and loss in the reflection in the ground. Some parts of the radio path may be in daylight and others in darkness. More than one layer may be involved. Muli-path distortion occurs. Peculiar things happen and much depends on frequency. The low-angle performance of a half-wave dipole, even when radiating broadside towards the receiver, is very poor in comparison with a simple vertical. On the other hand, a simple vertical does reasonably well when working just across county because of the short propagation path, almost straight up and down again, or even via the groundwave for very short distances. ---- Reg, G4FGQ. |
Verticals versus Horizontal Dipoles
Crazy George wrote:
By the way, how much of the UK is within 500 miles of your QTH? I have to exceed 500 miles just to get out of the state of Texas. Now George, I'll bet it's only a measley 420 miles. :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Verticals versus Horizontal Dipoles
Not counting Mexico.
-- Crazy George W5VPQ My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap. "Cecil Moore" wrote in message et... Crazy George wrote: By the way, how much of the UK is within 500 miles of your QTH? I have to exceed 500 miles just to get out of the state of Texas. Now George, I'll bet it's only a measley 420 miles. :-) -- 73, Cecil http://www.qsl.net/w5dxp |
Verticals versus Horizontal Dipoles
Opinions of the many individuals depend on geographic lattitude, World
population densities, what bands happen to be favourites, G5RV's and how much money there is in the bank. Let's try to remove these distracting factors. I'll put it in somewhat different "simplistic" terms. Everything else being equal, the deciding factors are geometry and trigonometry. The performance of a dipole is better at elevation angles greater than about 45 degrees and the performance of a vertical is better at lower angles. That's because the vertical and horizontal antenna types are oriented at 90 degrees to each other. At elevation angles around 45 degrees performance is about the same for both types. The ground path distance corresponding to 45 degrees depends on height of the ionospheric reflecting layers. Layer height depends on which layer, mainly E or F2, day or night, summer or winter, and the solar sunspot cycle. (None of these important factors are taken into account by antenna modelling programs. Propagation prediction programs DO take them into account but, with them, geometry is also an essential factor.) The range of distances at which vertical and horizontal antennas have similar performances in daylight is from 140 miles (E-layer) to 500 miles (F2-layer), which falls to 370 miles at night. But what decides whether a transmiiting antenna will be used or not is NOT the distance to the receiver - it is the MUF (maximum usable frequency) The MUF is geometrically-derived which increases with distance and with a decreasing elevation angle. It also changes with geographical lattitude and sun angle. With the F2-layer the MUF can increase by 3 times the vertical critical frequency Fcrit. Thus, by using a vertical low-angle antenna there are more bands and potentially more listeners available. Fcrit is the highest frequency which is reflected from a layer at vertical incidence. At higher frequencies the wave passes straight through. The MUF for high radiation angles and short distances is therefore low. It does not increase very fast as the radiation angle falls. It varies with night and day and the solar 11-year cycle. For the E-layer in summer daylight Fcrit is about 3.5 MHz. For the F2-layer in summer daylight it is about 6.5 MHz and about 5.5 MHz at night. On winter nights Fcrit for the F2-layer is about 3.5 MHz. Fcrit and high angle MUF's are subject to variation due to solar activity. But in general only the 80m and 160m bands, and sometimes 40m, are open for short distance rag-chews. This restricts the advantages of high-angle horizontal dipoles. Finally, a horizontal dipole radiates best when broadside on. Unless it is rotateable it has weaknesses in its service area. If I had to choose, I'd always choose a half-wave 80m vertical in preference to a half-wave dipole. ---- Reg. |
Verticals versus Horizontal Dipoles
On Wed, 1 Feb 2006 15:03:10 +0000 (UTC), "Reg Edwards"
wrote: [bafflegab snipped] If I had to choose, I'd always choose a half-wave 80m vertical in preference to a half-wave dipole. Me too, except that even with two acres, I can't meet the zoning setback requirements for a 135 foot tall tower. |
Finally, a horizontal dipole radiates best when broadside on. Unless
it is rotateable it has weaknesses in its service area. If I had to choose, I'd always choose a half-wave 80m vertical in preference to a half-wave dipole. ---- Reg.[/quote] all antennas are a trade off no antenna is better than some other antenna at everything what is better can be very subjective can you make it, do you half to buy it, can you aford it, do you have room for it, half to hide it from the neighbors, how high can you put it up, any big trees handy for hanging wires must your antenna work all bands from 80 to 10 or just be great on one or two bands what band, what use, rag chew, dxing, contest, what kind of test Cal. qso party is quite diffrent from CQ wpx 80 meter 1/2 wave vert is 130 ft high how many ops can put up a 130 ft vertical in their back yard store bought ground mounted multiband verticals good ones are expensive, nearly none are close to 1/4 wave high, and a good ground system is a must always lusted after a high gain high tower vert but they now sell for about 875 dollars u.s. and my xly is not about to let me tear up her flower gardens to lay out a ground system on 75/80 out to 750 miles a 1/4 wave vert is about as good as a dummy load good in the clear, big vertical is a great dx antenna but if you are going to dx with it on 160, 80, or 40 you are going to half to also put up a receive antenna verticals are horrid receive antennas on low bands as they pick up every bit of man made qrn 20 meter ground plane feed point at 35 or 40 ft is a wonderfull dx antenna lower bands horizontal pattern of horizontal half wave dipole do not come in to play unless at least 1/2 wave above ground dipole has been the most popular amateur radio antenna for over 60 years reason easy to make, easy to put up and keep up, for most general purpose use work very well which is better dipole or vertical, is a question that has no answer best antenna is the one you have up right now mac w8znx |
Verticals versus Horizontal Dipoles
If I had to choose, I'd always choose a half-wave 80m vertical in
preference to a half-wave dipole. In general, I'd prefer the dipole on 80m. But I work mostly close in within say 600 miles on average. A dipole will smoke most verticals at those short distances. If the dipole is at least 30-40 ft off the ground, it will still be capable of dx. If I worked all dx on 80, I'd rather have the vertical, but being I don't, I prefer the dipole. Each band is different, and it always depends on what path/distance etc, I want to work as far as the preferred antenna. In general, I'd prefer the vertical on 160m. Dipole for 80 and 40, and usually 20. I've tried both a 1/4 GP and a dipole on 20m for average use, and found I prefer the dipole. Probably ditto for 17,15. But on 10m, I prefer a 1/2, 5/8 vertical if I can't have a beam. On 10m, you see quite a bit of local chatter, and most tend to run vertical if they want a decent ground/space wave. It also gives them a good dx signal. If you run a dipole on 10m, your long haul will be good, but local operation fairly poor. There really is no best type antenna except to suit the job at hand. If I'm on 40m in the day, give me me a good dipole, loop, etc . But 40m at night 800-1000 miles to the coasts? I'd rather be sitting in my truck running the mobile. No joke. It will do a better job vs my appx 40 ft tall dipole. That was tested over and over again. No fluke of the band cdx. On 40 at night, which is best will nearly always be distance determined. Look at the lowly efficiency of the mobile vs the dipole. At night, it doesn't really mean squat. What matters is that you have radiation at the angle you need to make that hop. My mobile spits more rf at the desired angle than my 40 ft high dipole does at those semi low angles despite being half crippled as far as efficiency vs a full size antenna. So polarization is nothing to ignore if you want the best bang for the buck. I bet my mobile ant sitting sideways would be pretty lame in that case. Or say take two like mobile antennas and make a short dipole. It would stink up the place on those long hauls vs the normal vertical mobile antenna. But it might be slightly better in the day working 200 miles away. The best is to have both. :) And use a switch to be able to quickly compare. You will see some interesting things as far as band cdx, signal fluctuations, etc over time. It really boils down to using experience working the various bands, at the various times of day, season, to know which will likely be the best at a given time. It's 1.49 in the AM here right now. If I had to get on 40m right now, give me the vertical any day. That would change in a few hours though when I started losing the long haul stuff and had it replaced by the various old farts and rednecks I work on a more local scale. :/ I'd then be on the dipole. MK |
Verticals versus Horizontal Dipoles
|
Verticals versus Horizontal Dipoles
Reg, G4FGQ wrote:
"On the other hand, a simple vertical does reasonably well when working just across country because of the short propagation path, almost straight up and down again, even via the groundwave for a very short distance." True, but the thread is: "Verticals versus Horizontal Dipoles". Reg`s choice, I think. Verticals have a null toward the zenith which tends to impair their "straight up and down again" performance. The horizontal dipole`s nulls are at its tips, too, but are pointed elsewhere, not at the zenith. This mey actually avoid some noise and interference beyond that originating in the directions of straight up or down again. As much noise is vertically polarized, it may be rejected by ctoss-polarization. The horizontal dipole performs pretty well in the directions near the zenith when it is elevated at less than 1/2-wavelength in height, and for frequencies below the maximum usable frequency at near vertical incidence. At 1/2-wavelength elevation, the horizondal dipole develops a null toward the zenith, too. Propagation of H-F signals via the groundwave is for a very short distance indeed. Frequency has a pronounced effect upon sffective earth conductivity. Conductivity falls fast with increasing frequency due to skin effect. . The earth layer penetrated by the wave thins as frequency increases, making it less conductive and increases loss. For example, over soil of 10 mmhos/m, a fairly common value, a transmitter would have to ptoduce 1,000 times more power at 5 MHz to produce the same signal at 10 miles as would a 0.5 MHz transmitter. The earth`s attenuation of low-angle radiation from a 1/4-wave vertical antenna has a significant effect on the vertical radiation pattern. ee Fig. 54-1 on page 465 of B. Whitfield Griffith`s "Radio-Electronic Transmission Fundamentals". This figure shows field intensity curves versus vertical angle from a 1/4-wave vertical antenna radiating 1 kilowatt over earth of average conductivity. Anything below about 5-degrees is gone, eaten by the earth`s losses. I conclude that for high frequencies, unless you have good or very good conductivity soil, horizontal polarization will likely serve you better than vertical polarization. If you are at sea or immediately on the sea shore, you likely may do better with vertical polarization. There are so many variables that it would likely be best to have antennas of both polarizations available, and to use the antenna which gave the best signal in the particular instance. Best regards, Richard Harrison, KB5WZI |
Verticals versus Horizontal Dipoles
This is an early stage of the experiment, but
I believe that there is a lot to say with the lower noise on the horizontal antenna station Probably has a lot to do with the particular sites though. It's quite possible to be near a noise source that is mainly vertical polarized. In a case like that, it's possible it could be a problem. But I never saw the difference in noise levels you are seeing. At the worst, I might see appx 2 S units, but sometimes it might only be one, or even other times , nearly no difference at all. Most of the noise I would see at this location is power line noise. It seems to effect both horizontal and vertical nearly equally. :( Probably cuz much is radiated by horizontal power lines. I've never tested it, but I think if you are in a noiseless location, the difference would be fairly small as far as meter readings just measuring the average atmospheric noise. The reason I say this is because sometimes I would see little difference in noise between the two. But other times I might see more. But you could see small differences just from the increase in strength of dx signals. IE: if you had T-storms 1500 miles away, it's quite likely the vertical will receive them stronger than the horizontal due to the normal operation of the antennas. Anyway, I don't totally consider what you see as the norm. "4 s units" You probably have a local vertical noise source nearby. If it's power line, etc, you might be able to track it down and get it fixed. :) I'd be curious to see if you see the same 4 S unit noise difference over a period of time. Like I say, mine would vary. But noise never was much of a concern on mine. Never gave it much thought at all. Kinda weird too being I'm in a big city, in a residential area. Being mine was elevated at 36 ft at the base, I also had a pretty good line of sight to any potential noise sources. The tip of the radiator was at about 68 ft. As far as the VE being better on the wire, that's probably fairly normal, being he wasn't dx. Also, as a final note, while your butternut with 20 radials is ok, it still isn't quite up to the performance I saw with mine at 36 ft, using a full size antenna. So I saw a larger signal increase on the dx than you I bet. Mine was appx equal to a full length monopole with 60 radials, if ground mounted. I'd have to look, but my ground may be a bit better too. I'm right on the edge of being in a "30" zone. Of course, raising efficiency raises s/n equally, but I noticed that I never saw the same performance I had with the ground plane, when I ran the same full size vertical on the ground with 32 radials. That antenna was about equal to my dipoles at 1500 miles. Maybe a small bit better, but not any 2 S units worth like the GP was. So regardless of some saying the number of radials is not too important, it must be, if you want the best performance. Sure made a difference here... Either that, or elevating it above the surroundings makes the difference. Myself, I think it's about 75% the first, and 25% the second... Elevating the antenna for sure increased my local ground wave. I could work 50 miles away ground wave easy. I'd have cases in the daytime where I'd lose locals due to the band stretching out. But I could still nail them at S 9 using the GP, where the dipole would be hard to read backscatter. Of course, if the band was open short, I'd be 10-20-30 over 9 on the dipole to the same location. Anyway, I guess you gotta use what works, but I don't think it's totally normal to see a huge difference in noise between vertical and horizontal unless something local is the culprit. MK |
Verticals versus Horizontal Dipoles
"Richard Harrison" wrote:
The earth`s attenuation of low-angle radiation from a 1/4-wave vertical antenna has a significant effect on the vertical radiation pattern. ee Fig. 54-1 on page 465 of B. Whitfield Griffith`s "Radio-Electronic Transmission Fundamentals". This figure shows field intensity curves versus vertical angle from a 1/4-wave vertical antenna radiating 1 kilowatt over earth of average conductivity. Anything below about 5-degrees is gone, eaten by the earth`s losses. ________________ This certainly is not true for frequencies below about 2 MHz. If it was true, MW broadcast stations would have no groundwave coverage -- which of course is the only useful coverage they _do_ have in the daytime. A monopole vertical radiator of any length up to 5/8-wave, when used with a ground system of ~120 buried radials each ~1/2-wave long, radiates its peak field very nearly in the horizontal plane regardless of the conductivity of the ground in which the radials are buried. This gain is within a few percent of the theoretical peak gain for these radiators when working against an infinite, perfectly conducting ground plane, as was demonstrated by the field tests of Brown, Lewis & Epstein in 1937. This principle has been accepted and used by the FCC and other regulating agencies, and has been field-proven in thousands of installations going back many decades. Once "launched," the groundwave signal is affected by ground conductivity along the propagation path, earth curvature, obstructions etc. Groundwave path loss increases with increasing frequency, and above some frequency in the low HF range, the groundwave is unable to serve a practical purpose. But that doesn't necessarily mean that the transmit antenna did not generate the groundwave in the first place, ie, that it radiated zero field in the horizontal plane and at very low elevation angles. RF Visit http://rfry.org for FM transmission system papers. |
Verticals versus Horizontal Dipoles
My geometric argument that beyond distances of several hundred,
perhaps 500 miles, the vertical puts down a stronger signal and receives stronger signals than the horizontal dipole cannot be disputed. If you can't be heard at 1000 miles or more using a dipole, you are more likely to be heard using a vertical regardless of what antenna the other fellow is using to receive. At great distances you are much more likely to be heard using a vertical at the same average height above its surroundings. Signal to noise ratio does matter of course. Local noise level is much greater than received from distance sources for obvious reasons. Local noise is vertically polarised. It comes in via groundwave. Noise from a distance is randomly polarised. It comes in via the ionosphere. So in towns and cities, with buildings wiring, overhead power and phone lines, where most of us live, the vertical collects more local noise. In the wide open countryside both types of antenna tend to perform equally well on randomly polarised, distant noise levels. With distant noise and interference and distant signals, both types of antenna result in the same signal to noise ratio in the receiver. But the vertical antenna receives the stronger signal plus noise. If the internal receiver noise is greater than the received signal plus noise then the vertical antenna will win the contest. However, there is another effect which sometimes gives the dipole the advantage. It is multi-hop propagation. The angle of elevation of the radio path increases with the number of hops involved. The number of hops depends on the sun-angle and day or nighttime. Across the States or across the Pacific, for example, the propagation loss can be much less with 2 or 3 hops than it is with one or two hops. Waves sometimes bounce between the F2 and E layers. The increase in elevation angle favours the horizontal dipole. And how many amateurs know the number of hops involved at any point in time? But what eventually favours the vertical over the dipole is their respective service areas. The service area covered by the vertical is many times, far greater than the dipole and so is the world wide distribution of radio amateurs and short-wave listeners. We have now returned to the simplistic but precise Geometry of the ancient Egyptians and Greeks. ;o) ---- Reg, G4FGQ. |
Verticals versus Horizontal Dipoles
"Reg Edwards" wrote:
The low-angle performance of a half-wave dipole, even when radiating broadside towards the receiver, is very poor in comparison with a simple vertical. ________________ To the extent that this is true, it is not just a function of the intrinsic radiation patterns of the (horizontally polarised) half-wave dipole and the vertical monopole, but also to the net gain toward the other end of the path including reflections of that intrinsic radiation from the physical environment around the antenna. The performance of an antenna near the earth can depend as much on its installation conditions as its free space pattern. RF |
Verticals versus Horizontal Dipoles
"Richard Fry" wrote in message ... "Richard Harrison" wrote: The earth`s attenuation of low-angle radiation from a 1/4-wave vertical antenna has a significant effect on the vertical radiation pattern. ee Fig. 54-1 on page 465 of B. Whitfield Griffith`s "Radio-Electronic Transmission Fundamentals". This figure shows field intensity curves versus vertical angle from a 1/4-wave vertical antenna radiating 1 kilowatt over earth of average conductivity. Anything below about 5-degrees is gone, eaten by the earth`s losses. ________________ This certainly is not true for frequencies below about 2 MHz. If it was true, MW broadcast stations would have no groundwave coverage -- which of course is the only useful coverage they _do_ have in the daytime. A monopole vertical radiator of any length up to 5/8-wave, when used with a ground system of ~120 buried radials each ~1/2-wave long, radiates its peak field very nearly in the horizontal plane regardless of the conductivity of the ground in which the radials are buried. This gain is within a few percent of the theoretical peak gain for these radiators when working against an infinite, perfectly conducting ground plane, as was demonstrated by the field tests of Brown, Lewis & Epstein in 1937. This principle has been accepted and used by the FCC and other regulating agencies, and has been field-proven in thousands of installations going back many decades. Once "launched," the groundwave signal is affected by ground conductivity along the propagation path, earth curvature, obstructions etc. Groundwave path loss increases with increasing frequency, and above some frequency in the low HF range, the groundwave is unable to serve a practical purpose. But that doesn't necessarily mean that the transmit antenna did not generate the groundwave in the first place, ie, that it radiated zero field in the horizontal plane and at very low elevation angles. ========================================== Rich, all what you say is quite true - except that groundwave is radiated at ALL frequencies from a vertical of 5/8-wave or shorter. Useful propagation occurs at 30 MHz and below. But loss in the ground and loss due to obstructions above 1/4-wave in height is high. Solid ragchews across town and small city are quite possible on the 10m band. For predicting groundwave propagation from VLF to HF, download program GRNDWAV3 from website below. ---- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
Verticals versus Horizontal Dipoles
For predicting groundwave propagation from VLF to HF, download program GRNDWAV3 from website below. ====================================== Sorry, I should have said download program GRNDWAV4 from website below. ---- .................................................. ........... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
Verticals versus Horizontal Dipoles
Hi Reg
Interesting stuff I wonder however if you have any hard data on the merits of using one polarization over another in an electrically noisy environment. For years I have believed (but never seen proof) that on average horizontal is better for this. Any comments? If it is horiz, why? Is it indeed the high radiation angle missing local noise makers or something else..? Cheers Bob VK2YQA Reg Edwards wrote: There is much discussion about the relative merits of the simple vertical versus horizontal dipole antennas. |
Verticals versus Horizontal Dipoles
Interesting stuff I wonder however if you have any hard data on the merits of using one polarization over another in an electrically noisy environment. For years I have believed (but never seen proof) that on average horizontal is better for this. Any comments? If it is horiz, why? Is it indeed the high radiation angle missing local noise makers or something else..? Cheers Bob VK2YQA Reg Edwards wrote: There is much discussion about the relative merits of the simple vertical versus horizontal dipole antennas. ========================================== Local noise is stronger in terms of milli-volts per meter than distant noise for obvious reasons. It is nearer and man-made. Local noise is vertically polarised and comes in via the groundwave and at low elevation angles. Therfore, a vertical antenna which is most sensitive to vertical polarisation and to signals and noise coming from low angles produces greater low-angle signals and low-angle noise in the receiver. Whereas, distant noise comes in from high angles via the ionosphere and is randomly polarised. It is weaker than local noise. It depends on lattitude, the sun, day or night and season of the year. Therefore, a horizontal dipole which is most sensitive to signals and noise coming in from the higher angles produces greater high-angle signals and high-angle noise in the receiver. Now carry on from there. Compare a dipole receiving a low-angle signal with high-angle noise coming in from all directions, with a vertical antenna receiving a high-angle signal with low-angle noise coming in from all directions. ---- Reg. |
Verticals versus Horizontal Dipoles
"Reg Edwards" wrote in news:drqije$rqq$1
@nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com: Opinions of the many individuals depend on geographic lattitude, World population densities, what bands happen to be favourites, G5RV's and how much money there is in the bank. Let's try to remove these distracting factors. I'll put it in somewhat different "simplistic" terms. Everything else being equal, the deciding factors are geometry and trigonometry. The performance of a dipole is better at elevation angles greater than about 45 degrees and the performance of a vertical is better at lower angles. That's because the vertical and horizontal antenna types are oriented at 90 degrees to each other. At elevation angles around 45 degrees performance is about the same for both types. No, at 45 degrees the PATTERN is about the same (assuming that the horizontal antenna is at least .25 wavelength high). But the actual GAIN over an isotropic source is equivalent down at around 25 degrees. That's because the vertical is normally a monopole, the other half of which is reflected in the ground, whereas the dipole is a dipole and its ground reflection is therefore another dipole stacked with it. Ground losses for the dipole occur at a lower incident angle and further from the antenna and are thus lower. Of course, you can have the best of both worlds by using a vertical dipole, in which case your take-off angle will really be quite low. The main reason why verticals tend to outperform dipoles on low-band DX paths is that the dipoles and other horizontally polarized wires are rarely very high. A lot of them are only about an eighth of a wavelength up or even less. This increases ground losses at all angles and reduces the efficiency of the antenna. And if you can get the current loop to climb up the antenna (by top loading it), a vertical will compete very strongly below about 30 degrees. -- Dave Oldridge+ ICQ 1800667 |
Verticals versus Horizontal Dipoles
Reg wrote:
"If you can`t be heard at 1000 miles or more using a dipole, you are more likely to be heard using a vertical regardless of what the other fellow is using to receive." That must not always be the case. Otherwise all the shortwave broadcast stations I`ve worked in, and seen for that matter, would not use horizontal antennas. They have no way of knowing what their audience will use for antennas, and it does not make much difference as following ionospheric reflection, all wave polarizations are available and may be received. At the equator, a time zone is about 1000 miles wide. at the poles (a bad place for shortwave propagation) the width of a time zone is insignificant. All the stations I refer to are in the temperate zone and their targets are likely 1000 miles or so away, though some targets of some stations are only a few hundred miles away. Antennas at these shortwave broadcast stations are a product of studying successful antennas and carefully designing new antennas anf testing their performance in and around their intended targets. They are proved to be effective. Why would a vrtical antenna be better? From Arnold B. Bailey`s giant antenna catalog in his "TV and Other Receiving Antennas", the free-space gain is the same for a ground plane as it is for a center-fed 1/2-wave dipole. An antenna`s proximity to the earth may change the balance between horizontal and vertical antennas. Terman writes on page 886 of his 1955 edition: "Consider an antenna that is far enough from ground so that the total power radiated by a given set of antenna currents is independent of the presence of the ground. Then a ground reflection that reinforces the main lobe will double the field strength of the main lobe, and so will increase directive gain of the antenna system by a factor of 4. This condition corresponds to an antenna height great enough to make the mutual impedance between the antenna and its image small (see page 894).With horizontally polarized systems this will be the case if the center of the antenna is at least one wavelength above ground; with vertically polarized systems it is true even at lower heights. However. when the antenna is sufficiently close to the ground the effect of the ground reflection is to cause the directive gain to differ from 4. Thus , for a vertical doublet close to the ground, the directive gain is twice the free-space value, since the presence of the ground does not alter the directional pattern and there is no energy radiated in the direction of the hemisphere occupied by the ground. In contrast, the directive gain of a horizontal antenna very close to the ground can be more than 4 as compared with the same antenna in free space, as discussed below in connection with Fig. 23-36." Seems horizontal antenna users are not fools after all. Best wishes, Richard Harrison, KB5WZI |
Verticals versus Horizontal Dipoles
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Verticals versus Horizontal Dipoles
On Thu, 02 Feb 2006 21:57:47 -0500, Mike Coslo
wrote: But here is the interesting thing. On the horizontal antenna, the listening is a whole heckava lot more pleasant. Another item of interest Mike, you will be aware that a lot of commercial HF amateur transceivers have two HF antenna sockets which can be selected from the front panel. I have always wondered why they do not support a mode of tx on Ant-1, rx on Ant-2 to conveniently support the very configuration you are using. Owen -- |
Verticals versus Horizontal Dipoles
Mike Coslo wrote:
. . . I gotta get these two meters calibrated against each other. . . . If you don't have a signal generator with variable output, connect the two feedlines through a DPDT switch so it swaps the antenna to each receiver when you switch it back and forth. Write down the meter reading on each receiver for the same signal from the same antenna. It probably won't take long to accumulate a decent cross reference. Of course, you still won't have a clue as to how many dB each meter unit represents. That'll take an investment of a few dollars and an evening to make a step attenuator. Roy Lewallen, W7EL |
Verticals versus Horizontal Dipoles
Owen Duffy wrote:
On Thu, 02 Feb 2006 21:57:47 -0500, Mike Coslo wrote: But here is the interesting thing. On the horizontal antenna, the listening is a whole heckava lot more pleasant. Another item of interest Mike, you will be aware that a lot of commercial HF amateur transceivers have two HF antenna sockets which can be selected from the front panel. I have always wondered why they do not support a mode of tx on Ant-1, rx on Ant-2 to conveniently support the very configuration you are using. I'm inclined to agree. I guess I'll have to build a switching box. Shades of olde time separate transmit/receive rigs! - 73 de Mike KB3EIA - |
Verticals versus Horizontal Dipoles
On Sat, 04 Feb 2006 03:26:46 -0800, Roy Lewallen
wrote: represents. That'll take an investment of a few dollars and an evening to make a step attenuator. A greatly overlooked item of test equipment. I recall advising a ham to buy a HP355 step attenuator so that he could quantify the level of interference from nearby power leaks and build a prime facie case for non compliance with emission standards. Although he had just winged at length about his $20,000 plus investment in a tower and VHF/UHF antennas, more on radios, etc... he baulked at spending a $100 on something as unexciting as a step attenuator. This was an opportunity to learn a little more about predicting path loss than a $100 burden. As part of my FSM project for measuring BPL emissions, I went searching the net for kits for RF step attenuators, and all that I found were kits that had gone obsolete, no longer available. Today it should be a piece of cake to do a low cost kit with miniature switches, precision surface mount resistors etc... but we as a community are apparently not sufficiently interested in quantifying things these days. Owen -- |
Verticals versus Horizontal Dipoles
Owen Duffy wrote:
. . . As part of my FSM project for measuring BPL emissions, I went searching the net for kits for RF step attenuators, and all that I found were kits that had gone obsolete, no longer available. Today it should be a piece of cake to do a low cost kit with miniature switches, precision surface mount resistors etc... but we as a community are apparently not sufficiently interested in quantifying things these days. A step attenuator which is completely adequate for HF and can easily resolve 1 dB can be made from a few cheap slide switches, some PC board material, and a handful of ordinary 5% quarter watt resistors. Detailed instructions can be found in numerous sources, including the Web -- a Google search brought a large number of hits, the first of which was http://www.arrl.org/tis/info/pdf/9506033.pdf. But I'm afraid that this level of homebrewing is beyond the interest if not the ability of the majority of today's amateurs. Roy Lewallen, W7EL |
Verticals versus Horizontal Dipoles
"Owen Duffy" wrote but we as a community are apparently not sufficiently interested in quantifying things these days. ========================================== "When you can measure what you are speaking about and express it in numbers you know something about it. But when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. It may be the beginning of knowledge but you have scarcely in your thoughts advanced to the state of science." : William Thomson, Lord Kelvin, 1824-1907. ========================================== Arithmetic is not taught in Western schools and universities any more. Even teachers are innumerate! ---- Reg. |
Verticals versus Horizontal Dipoles
Tnxs for that Reg
What is the generally accepted "number" in either S points or dB of employing horizontal instead of vertical for noise reasons? Obviously it would vary greatly but any idea you have would be helpful. I would also like to get an idea how "critical" it is to make sure ones antenna truly is horizontal (eg not an inverted V or quad loop) if noise is the greatest concern. One would assume you also get a similar affect of "less horizontal noise" from the actual noise source for the same reason. eg power lines radiate well upwards but not so well in groundwave. Cheers Bob W5/VK2YQA Reg Edwards wrote: Local noise is stronger in terms of milli-volts per meter than distant noise for obvious reasons. It is nearer and man-made. |
Verticals versus Horizontal Dipoles
"Bob Bob" wrote - Tnxs for that Reg What is the generally accepted "number" in either S points or dB of employing horizontal instead of vertical for noise reasons? ========================================= Bob, First of all we must entirely disregard the opinions of individuals who may be located in high or low noise districts, areas or regions. I myself live in an industrial, densely populated, area near to a factory with a dozen electrical arc welding machines. Others live out in the wilderness, isolated from modern, electrical noise generating civilisation. There exist statistics of AVERAGE field strength noise levels experienced in cities, small towns and in the open countryside. I have forgotten where to find such statistics but Google may help. The statistics depend very much on frequency. They vary greatly between ELF and HF. Noise levels decrease by crudely 10 dB or 20 dB per octave or decade increase in frequency. Furthermore, at ELF and VLF, noise propagates to far greater distances than at HF. There are always continuous world-wide electrical storms somewhere on the Earth's surface. At 10 KHz noise levels may be several hundred milli-volts per meter. At 7 MHz they may be microvolts per meter. At 30 MHz they are of the order of the internal receiver noise. The noise level indicated by your S-meter is a function of the size of the antenna relative to wavelength and antenna efficiency. It can be crudely calibrated in terms of micro-volts per metre using a little arithmetic. Learn how to estimate. In my own experience (which as I say should be disregarded) the difference in noise level between a horizontal dipole and a vertical is about one or two S-points on the 160 metre band. (Or a difference of 6 or 12 dB.) On the other hand, distant stations come in stronger using a 150-feet, vertical (inverted-L) than they do on a dipole. Not that I have ever used the two types of antenna simultaneously. It's just my opinion. So I prefer the inverted-L. In general, the signal to noise ratio is better and there is less fading. One hop instead of two, via the F2-layer, at night, using a dipole? ---- Reg, G4FGQ |
Verticals versus Horizontal Dipoles
Reg Edwards wrote:
There exist statistics of AVERAGE field strength noise levels experienced in cities, small towns and in the open countryside. I have forgotten where to find such statistics but Google may help. The statistics depend very much on frequency. They vary greatly between ELF and HF. Noise levels decrease by crudely 10 dB or 20 dB per octave or decade increase in frequency. ITU Recommendation ITU-R P.372-8, 'Radio Noise'. This document replaces and updates the old CCIR Report 322, which was the source for most of the information on radio noise in the amateur handbooks. The paper is available as a download from ITU, but they want 36 Swiss Francs for it (about $28): http://www.itu.int/rec/R-REC-P.372-8-200304-I/en -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Verticals versus Horizontal Dipoles
Reg: Your making such an obviously false statement calls into question
all of your pronouncements. There is not a single student in my University (or any other similar institution that I know of) who will graduate without providing many demonstrations of their significant arithmetic and mathematical ability. Your veracity is gone. Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "Reg Edwards" wrote in message ... ========================================== Arithmetic is not taught in Western schools and universities any more. Even teachers are innumerate! ---- Reg. |
Verticals versus Horizontal Dipoles
On Sun, 5 Feb 2006 22:50:55 -0500, "J. Mc Laughlin"
wrote: Reg: Your making such an obviously false statement calls into question all of your pronouncements. There is not a single student in my University (or any other similar institution that I know of) who will graduate without providing many demonstrations of their significant arithmetic and mathematical ability. Your veracity is gone. C'Mon Mac, Reggie has been doing this so many years, it's his trademark schtick. To give Reggie credit where credit is due, can be found in a remarkable body of work of programs. Unfortunately, this accomplishment is seriously tipped out of balance when he scorns his audience as software addicts. Instead of teaching them Kelvin's principles by example, we get his poor English stagings of Le Misanthrope de Moliere. One of my favorite irascible English characters is Dr. Samuel Johnson, but his ire is tempered with a faith in humanity: "this boy rows us as well without learning, as if he could sing the song of Orpheus to the Argonauts, who were the first sailors.' He then called to the boy, 'What would you give, my lad, to know about the Argonauts?' 'Sir (said the boy,) I would give what I have.' Johnson was much pleased with his answer, and we gave him a double fare. Dr. Johnson then turning to me, 'Sir, (said he) a desire of knowledge is the natural feeling of mankind; and every human being, whose mind is not debauched, will be willing to give all that he has to get knowledge.' " 73's Richard Clark, KB7QHC |
Verticals versus Horizontal Dipoles
"Bob Bob" wrote I would also like to get an idea how "critical" it is to make sure ones antenna truly is horizontal (eg not an inverted V or quad loop) if noise is the greatest concern. One would assume you also get a similar affect of "less horizontal noise" from the actual noise source for the same reason. eg power lines radiate well upwards but not so well in groundwave. ======================================== Bob, The angle of the 'horizontal' dipole relative to the horizontal, whether it is an inverted-V or not, makes negligible difference to the amount of noise it collects. It is non-critical in this respect. The incoming, mainly distant noise comes in from all directions and angles and is randomly polarised. Except, that is, for locally generated noise, which is mainly a vertically polarised ground-wave and from low angles to which the horizontal dipole is quite insensitive. Noise radiated from nearby elevated power lines is probably randomly polarised and is collected in similar proportions by both horizontal and vertical antennas. When a power line is half-mile or more away I would guess that the received noise reverts to vertically polarised groundwaves which at HF are rapidly attenuated. The horizontal waves are even more rapidly attenuated. Noise can be studied only from its statistical probability distributions versus direction, angle, frequency, receiver bandwidth and time. The opinions and anecdotes of individuals matter only to the inviduals concerned and their locations on the Earth's surface. ---- Reg. |
Verticals versus Horizontal Dipoles
Roy Lewallen wrote:
A step attenuator which is completely adequate for HF and can easily resolve 1 dB can be made from a few cheap slide switches, some PC board material, and a handful of ordinary 5% quarter watt resistors. Detailed instructions can be found in numerous sources, including the Web -- a Google search brought a large number of hits, the first of which was http://www.arrl.org/tis/info/pdf/9506033.pdf. But I'm afraid that this level of homebrewing is beyond the interest if not the ability of the majority of today's amateurs. Got it - Thanks, Roy! - 73 de Mike KB3EIA - |
Verticals versus Horizontal Dipoles
Reg, G4FGQ wrote:
"The angle of the "horizontal" dipole relative to the horizon, whether it is an inverted V or not, makes negligible difference to the amount of noise it collects." It could be taken to the extreme. Rotated 90-degrees, the horizontal wire becomes a vertical wire. On its way to becoming a vertical wire, it is a sloping wire. The sloping wire responds with a vertical component in addition to its horizontal component. The sum of these components make up the wire`s total response. To the best of my knowledge, Reg hit the nail squarely on the head in the rest of his posting about noise radiation and reception. Best regards, Richard Harrison, KB5WZI |
Verticals versus Horizontal Dipoles
Regardless of its noise properties, a quarter-wave and higher vertical
radiates more low-angle power than a half-wave horizontal dipole. There's no argument. If you can't be heard then you can't work 'em. Although a quarter-wave vertical radiates less power at high angles, it can still be heard quite well because propagation distances covered are relatively short. The vertical is omni-directional. The dipole is not. Skip-distances are the same for both vertical and horizontal. The Ancient Greeks Geometry rules. Therefore, the situation is biassed in favor of the vertical. The dipole wins only when the local noise level is much higher than atmospheric noise. If you live in or near a city then its your hard luck. Most of us do! ---- Reg. |
Verticals versus Horizontal Dipoles
Mike Coslo wrote:
Roy Lewallen wrote: A step attenuator which is completely adequate for HF and can easily resolve 1 dB can be made from a few cheap slide switches, some PC board material, and a handful of ordinary 5% quarter watt resistors. Detailed instructions can be found in numerous sources, including the Web -- a Google search brought a large number of hits, the first of which was http://www.arrl.org/tis/info/pdf/9506033.pdf. But I'm afraid that this level of homebrewing is beyond the interest if not the ability of the majority of today's amateurs. Got it - Thanks, Roy! - 73 de Mike KB3EIA - You're very welcome. The reason for my rather grumpy comment at the end is that I've recommended countless times for many years that people interested in evaluating antennas build a simple step attenuator -- an evening project. It allows you to make direct, quantitative comparisons between two antennas -- yours or someone else's, as well as calibrate your "S" meter. But to date, I've never gotten an iota of feedback that a single person has actually taken the trouble to build one. Rather, they continue to debate, ad nauseum and without any meaningful data, whether one antenna is better than the other, or at best quote differences in "S-units" read from their meters, without the foggiest idea how many dB it might represent or how different it is from someone else's meter (or from the same meter on a different band or a different part of the scale). The conclusion I've reached is that A) Hams would much rather argue than actually determine the facts, or B) The vast majority are unable to build a homebrew project consisting of slide switches, circuit board material, and resistors. I'm afraid both are probably true. Maybe you'll be the first to actually build one. If so, please drop me an email and let me know -- it'll make my day! Roy Lewallen, W7EL |
Verticals versus Horizontal Dipoles
"Roy Lewallen" wrote The reason for my rather grumpy comment at the end is that I've recommended countless times for many years that people interested in evaluating antennas build a simple step attenuator -- an evening project. ======================================== Roy, to cheer you up, many years back I made one in a diecast Eddystone box. The last decade was in 0.001 dB steps. It was intended only up to 5 MHz. It was used to determine the attenuation/temperature coefficients of oceanic, submarine coaxial cables, 26 miles long, in tanks at the cable factory. Temperature was changed by dumping a ton of ice into the tank, obtained from Billingsgate, London, fish market. I think the fish market is still in Billingsgate but the attenuator has long since disappeared. Perhaps the knobs still exist somewhere. Very sad! ---- Reg. |
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