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"Richard Harrison" wrote in message ... Reg, G4FGQ wrote: "It`s purely a matter of Spherical Geometry" Edmund A. Laport agrees with Reg in his book "Radio Antenna Engineering". On page 227 Ed writes: "If, for example, the computed vertical beam angle for a one-hop circuit uses 6 degrees at an azimuth of 332 degrees and the horizon in this direction consisted of a mountain range with a height of 8 degrees, the performance of the circuit would be greatly compromised by the obstruction of the mountains. In such a case it might be better to work this circuit with two hops. Then a vertical beam angle of 20 degrees can be used instead, with adequate horizon clearance for the wave path. Or if the circuit required 6 degrees for a two-hop circuit 5400 kilometers long, with the same obstruction cited, one could change to a three-hop circuit which for the same layer height would permit the use of a beam at 14 degrees." Best regards, Richard Harrison, KB5WZI OR ....... you take advantage of diffraction abilities of physical parts such as mountain edges or other physical parts that can deflect the rays AFTER it leaves the FEED POINT which does NOT exclude an antenna array of which the feed point is part. The point of confusion emanates from.calculating hop distance on the basis of a :"standard:". TOA The "magic" of a stacked antenna exposes the difference :that occurs with a different TOA. I suppose you could use Reg's program so that when the ideal conditions do occur maybe after several hours of waiting , when one can say that the upper layers are now exactly such or such a height and the assumption used in formulating the program are now correct. The fact is that ham radio is about formulating an array that will provide the hop distance required by the operator since that is something he can change. I am quite sure that LaPorte does NOT say that no amount of shaking an antenna can change the hop distance which is what TOA is all about and the subject of this thread. Maybe we need another thread to clarify the question that Reg and yourself are apparently addressing. Art |
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