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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. |
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