[TowerTalk] Propagation / Beam Headings Responses

[n4kg@juno.com]

K3KO asked an interesting question which I responded to as
follows.   N4KG

On Sun, 17 Sep 2000 alsopb <alsopb@gloryroad.net> writes:

> Tom,
> 
> If one uses VOCAP doesn't one put in the actual sunspot number, 
> month and day of year?  Does this not give predictions for actual
> expected not average conditons?

	The most detailed results give different percentiles,
	such as upper 90%, upper 50%, and upper 10%
	so the absolute peak is always higher than the 
	published numbers.	

	Other factors also come into play such as ERP
	of both stations and antenna heights, possible E-layer 
	enhancements / bending which allows an otherwise 
	marginal opening to get a start.  Foreward scatter
	can also come into play.

	And finally, it is not an exact science so day to day
	variations come into play when you are skating on
	the edge of the MUF.

de  Tom  N4KG

> 
 
> n4kg@juno.com wrote:
> > 
> > Sylvan,
> > 
> > Propagation prediction tools are useful IF you recognize their
> > limitations.
> > 
> > First, since they are based on AVERAGES, they typically
> > underestimate peak MUF.  
> > Theoretical models of ANTENNAS have been shown to be
> > accurate.  IMHO, simplistic propagation prediction programs
> > leave a LOT to be desired.  Theory must be backed up by
> > observation and confirmation.

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