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Richard Fry wrote:
. . . ?? My reading of these NGs shows that many/most amateur radio operators ignore/discount the fact that the peak radiation launched by a vertical monopole of 5/8 lambda or less in height ALWAYS occurs in the horizontal plane., regardless of the operating frequency, or the r- f ground in use. I don't think most amateurs care about the locally launched radiation, except when dealing with local RFI. That low angle radiation decays to essentially nothing within a few miles at HF and even less at VHF and above. So it's of no use for communicating beyond a few miles. The radiation/reception characteristics at low elevation angles of such an antenna can be useful in establishing contacts with the most distant possible single-hop DX sites, can they not? RF They can not. I see you're still a bit confused about what happens to that ground wave signal. Beyond a few miles at HF, that low angle radiation decays to essentially zero. The pattern of the field beyond that distance resembles the one reported by EZNEC and other programs giving distant far field data. And they correctly show that unless the ground has very high conductivity at the reflection point, there will be very little field remaining at very low angles beyond that ground wave decay distance. The performance of an antenna when communicating with a distant station is precisely what EZNEC is attempting to show you. If you want to know how it will do at various elevation angles for DX, or even at distances of a few hundred miles, look at those plots. At HF, ground wave analysis will only tell you how well the antenna will do when talking with someone across town. Which is why there's very little interest in ground wave analysis among amateurs, HF broadcasters, or just about anyone except AM broadcasters. Roy Lewallen, W7EL |
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