Topband: Modeling the proverbial "vertical on a beach"

[Michael Tope]

On 8/15/2014 6:51 AM, Tom W8JI wrote:
>
> For receiving, an absence of noise sources in the path is all the 
> difference in the world. As an example of this look at what N7JW and 
> K7CA did from the Utah desert area. Utah desert is like the 
> anti-saltwater, and they are located much further from Europe than the 
> east coast with a worse polar area path, yet they had outstanding 
> results. Saltwater has the same advantage, as do freshwater bodies, of 
> a lack of noise sources in what might be a desired direction.
>
> For efficiency (which only affects transmitting), the advantage is 
> primarily concentrated at low angles and primarily affects vertically 
> polarized systems. The question then becomes one of wave angle and 
> polarization.
>
> Then there is distance as a factor, and path loss related to the 
> magnetic poles, which are factors.
>
> A good station has a combination of everything going for it, but there 
> is no magic and there certainly isn't any 10 dB or more involved just 
> from being near saltwater. A few dB here and there from multiple 
> factors are what make the difference. Move 25% or 50% closer, get rid 
> of noise sources in the path, increase vertical antenna performance at 
> low angles a few dB, and get away from going past the magnetic poles 
> and it is a winner. It isn't from magic, and it isn't all from the 
> presence of saltwater, and it is not 10-20 dB by any stretch of the 
> imagination.
>
> 73 Tom

I agree with what you say, Tom, but as others have pointed out, this 
still leaves the door open for an advantage at very low takeoff angles. 
A mostly unexploited propagation mode at very low takeoff angles could 
explain all the anecdotes from mobile operators which describe signals 
peaking as they drove up to waters edge and fading as they moved away. 
Also, this hypothesized low-takeoff propagation mode isn't necessarily 
at odds with the sunset/sunrise high angle mode (low dipole suddenly 
beats the vertical) that many have observed (IIRC, yourself among them). 
Myself I can imagine two distinct propagation modes, one at high angles 
and one at very long angles. They could, but wouldn't necessarily occur 
at the same time. What is needed is a really good test protocol and 
someone willing to do the work necessary to follow it.

73, Mike W4EF.........................