Topband: Skywaves from Monopole Surface Waves

[Guy Olinger K2AV]

Yes.  But again, does that mean ANY vertical radiator automatically gets
the low angle radiation no matter what?  Does this persist for me working
Russians on 160, or is it lost.  Is the notch correct if we are talking 500
miles not over salt water?   Why does the guy with the 4 square on
saltwater at Chesapeake Bay have such a louder signal if everybody gets the
low angle because the notch at zero is a myth.  Clearly everybody doesn't.
 What are the modifiers, and what data from non-local measurements truly
explain what happens when I try to work Russians from Raleigh if I've
always got my low angle?

73, Guy.

On Mon, Oct 8, 2012 at 6:28 PM, Paul Christensen <w9ac at arrl.net> wrote:

> Mr. Fry supplies a monolithic, complete fill up to three degrees at some
>> unspecified frequency over unspecified ground out 2.8 km.  The difference
>> between that and the NEC pattern generated for 1/4 wave over 120 0.4
>> radials at three degrees elevation is over seven dB.  That is a LOT of
>> fill.
>>
>
> I recently modeled the WLS-AM radiator, using the dimensions and ground
> system provided by my former supervisor, Warren Shulz, who recently retired
> from WLS after working for more than 40 years in Chicago broadcast
> engineering.
>
> When using NEC 4 during the WLS modeling, the vertical profile also shows
> (as expected) an infinite notch at zero degrees elevation over moderately
> good soil.   What the far field model of NEC does not show is the
> significant radiation at low elevations.  For that, a surface wave tool is
> required like the one that comes with 4Nec2.
>
> If we were to only believe in the NEC far field computation, AM braoadcast
> would have met its death in the early 1920s -- for nobody would be able to
> hear the stations except at night when the upper angle radiation could
> utilize the ionosphere.
>
> To get a complete picture of the vertical profile over soil really
> requires a meshing of the two data.  So far, I don't think any of the
> modeling authors have expressed an interest in creating a hybrid analysis
> tool.  NEC is providing the raw data and its accurate.  But we need a
> better form of display that integrates the far field with the surface wave.
>
> As W8JI pointed out, this is nothing new.  Academics like Terman, BL&E,
> et. al. were teaching it back in the early 1930s.  But we've become firm
> believers in the typical vertical profile field plots when the only
> accurate vertical profile result from a vertical radiator is produced from
> a vertical over a super-conductive surface like salt water.  There's
> nothing wrong with the far field plot, but we should realize its limitation
> in the context of the vertical profile, especially on topband.
>
> Paul, W9AC
>
>
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