Topband: Modeling the proverbial "vertical on a beach"

[Yuri Blanarovich]

Modeling programs are an excellent tool to calculate and predict some 
properties of antennas - radiators.
What they do not "see" is the propagation mechanism after RF leaves the 
antenna. "Space wave" can be "hugging wave".

While the high frequencies signals behave more like high frequency 
sounds - propagating in the straight line, hitting the ionosphere and 
then reflecting or refracting and continuing on.
Lower frequencies tend to propagate similarly as low frequency sounds - 
"flooding" the medium. On 160 and 80 we see signals "flooding" the 
medium with hardly any dead spots or zones, except some long haul path, 
where some focusing and ducting comes to play. I tried to elaborate on 
ways we propagate on HF in my article  
http://www.k3bu.us/propagation.htm

I have observed that, say on 160 low angle signals, such as produced by 
the salt water locations, seem to "hug" the Earth surface curvature, 
appears to be ducting, refracting, rather than "bouncing" off the 
ionosphere. We know that low band signals are "flooding", refracting, 
ducting, signals without dead zones, unlike we do experience propagation 
on high bands.

Polarization, its rotation in media, is another factor that modeling 
doesn't capture.
Long haul and focusing is on the mercy of propagation conditions.

We have to look at the antenna (radiator, radials, etc.) as RF source, 
analogous to light bulb.
Environment, ground conditions, surroundings, analogous to mirror(s) 
affecting, participating in the beam shaping and efficiency of the 
antenna. Modeling is an excellent tool for that.
Propagating media, air, ionosphere, as a "wire" carrying our signals. 
Propagation modeling can do some help here.

Tailoring each of those factors and variables for the best fit gets best 
results.
Then we have long delayed echoes that make us wonder what is going on.
I keep wondering if Earth - air - ionosphere - VanAllen belts - space is 
some kind of giant vacuum tube or resonator that enhances RF signals?
Tesla calculated the capacitance and self resonant frequency of 
Earth....

73 Yuri, K3BU.us
 
 
 On Wed, Aug 13, 2014 at 09:34 AM, Richard Fry wrote:
 
 > The link in the opening post of this thread shows an interesting, 
animated analysis of the elevation gains of a monopole, based on a NEC 
far-field analysis not including the surface wave.
>
> I then posted this comment, "Reality is that radiation leaving the 
> monopole at elevation angles of at least 5 degrees decays at a 1/r 
> rate. Therefore that radiation is a space wave which propagates in a ~ 
> straight line to reach the ionosphere, where (with suitable 
> conditions) it can return to the earth as a skywave."
>
> Others have been skeptical that this low-angle radiation was a space 
> wave that could reach the ionosphere.
>
> Recently I investigated this more closely, leading to the NEC4.2 study 
> linked below.  It shows that the 3.8 MHz radiation existing on a 
> departure angle of 5 degrees at a distance of 3/10 of a mile from a 
> monopole continues on toward the ionosphere along that path, while its 
> value decays at a 1/r rate -- indicating that it is a space wave.
>
> 
> http://s20.postimg.org/6yau4m225/Monopole_Radiation_5_deg_Departure.jpg
>
>
> _________________
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>