So here's a question. I have a vertical mounted on a cliff side that performs incredibly. My amateur's approach to figuring out why is that I modeled it in EZNEC as being elevated 400 feet. That shows it performing nearly as well as if it were on a tiny island in the great ocean.
Is it correct that an elevated feed point greatly reduces the ground losses? On Dec 13, 2012, at 12:35 PM, Guy Olinger K2AV <olin...@bellsouth.net> wrote: > I have already spoken extensively that your assertion is not proved, NOR is > the counter-assertion proved. I have no intentions of adding to that. I > am not persuaded either way, though BOTH sides of that question have > attractive points. I am waiting for something new to emerge, like > helicopter measurements out 50 km from operational ceiling down to the > ground. Since the near field NEC4 predicts the notchless 3 or 4 km > helicopter measured data, we have to get it out where the NEC process > predicts the notch and measure it there. That will settle it. If it > maintains down to the ground, then we can beat the LLNL people to death > with it and they will have to fix NEC. Otherwise, we don't know. > > To the point in question, you are asserting that if the notch under the > typical far field elevation plot was filled in, THAT would account for the > 4 dB? > > I give you that the loss would lessen if the gain at the ground was equal > to say 15 degrees and smooth going up, but the integration of the spherical > far field data asserts that OVER HALF THE POWER is going to loss. The only > way you get that back is to put it over sea water. Anyone experiencing the > marvelous increase in vertical performance at the edge of/over sea water > will tell you emphatically that you DO get it over sea water and you > decidedly DO NOT get that over inland dirt. Frankly the difference seems a > lot more than the difference in the plots. > > Filling up 20 degrees out of 360 will won't get you back to only 3 dB down. > The original question still stands. It is not related to your assumption, > or not. > > Anyone wants to tackle the idea that the far field plot of NEC4 is off by 4 > dB, in order to keep from acknowledging heavy foreground induced ground > loss, have at it. It should be interesting. > > 73, Guy. > > On Thu, Dec 13, 2012 at 7:06 AM, Richard Fry <r...@adams.net> wrote: > >> Guy Olinger wrote: >> >>> You can model a near perfect commercial grade radial field, with a radial >>> system apparent series resistance of a few tenths of an ohm, and NEC4 will >>> still come back with an overall loss of 3 to 4 dB. >>> >> >> This is ~true only for a "far field" analysis (as defined by NEC software) >> for a vertical monopole -- which includes the propagation losses present in >> the radiated fields from that monopole, over an infinite, FLAT, real-earth >> ground plane. >> >> > _______________________________________________ > Topband reflector - topband@contesting.com > _______________________________________________ Topband reflector - topband@contesting.com