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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 |
#2
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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. |
#3
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Verticals versus Horizontal Dipoles
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#4
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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 -- |
#5
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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 - |
#6
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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 |
#7
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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 |
#8
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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. |
#9
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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 .................................................. .......... |
#10
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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 .................................................. .......... |
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