To: <topband@contesting.com>
> Date: Wed, 18 Mar 1998 12:21:55 -0500 (EST)
Hi Earl and all,
> Regarding Tom W8JI's comments re his conversations with Roy Lewallen,
> W7EL about NEC-2: when he designed EZNEC, Roy incorporated a
> "high-accuracy" (NEC Sommerfeld) ground which he claims to be accurate
> for low horizontal wires down to .005 wavelength high (about 2.7 feet on
> 160m).
I'm not sure if that's Roy's position, or if he is relying on (or
repeating) NEC data supplied to him.
> Regardless of modeling results, I remain to be convinced either way,
Myself also. While the disagreement could be only at some sites (it
could be an artifact of the deep skin depth on 160), N7CL's report
indicates an accuracy problem exists on higher frequencies.
When thinking in terms of EM theory and how fields interact, it
makes no sense at all that a sparse radial system close (within 1/4
wl or so) of earth should offer some large advantage over a full
radial system.
Textbooks agree with the basic analysis N7CL presented, yet a few
"papers and articles" seem to disagree. I'll take peer-reviewed and
time proven science over a model or personal paper any day.
This is especially true since one of the articles referenced as a
"pioneering work" in supporting this new theory contains measured
data that directly violates Kirchhoff's law. IMHO, a disagreement
with Kirchhoff's law in measured data indicates a serious flaw.
>Note that the modeling results or for gain at the
> optimum takeoff angle. Perhaps the 5dB figure is true for ground wave
> (zero degree takeoff), which NEC models cannot show (they show zero
> signal at zero degrees).--???
NEC can calculate ground wave FS, it's only the abbreviated programs
we run on our small PC's that look at the field at a far distant
point where ground effects have taken the field to zero. We all know
verticals do have useful groundwave.
73, Tom W8JI
w8ji.tom@MCIONE.com
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