Topband: Fw: GAP VERTICAL QUESTION

[Ashton Lee]

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 <olinger at 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 <rfry at 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 at contesting.com
>