[TowerTalk] HFTA Angles Data

[David Robbins]

ssn to ionization density is just one part of the equation, you have to also consider layer height and even the effects of other layers than just the F layer.
you should also expect voacap and other ionospheric modeling packages to produce similar results as they have been created by similar processes
that account for the whole range of variables.  even my MOF/LOF calculator (http://www.k1ttt.net/technote/techref.html#prop) which was derived from 
minimuf85 was fitted to a solar cycle's worth of contest data from around the world, though mine took the extreme route of finding even the weakest possible
paths instead of the broadcaster or traffic handler optimum frequencies it provides a similar range of arrival angles.  

The use of anything like the hfta figure of merit has to be weighted to what your goals are... i.e. in contesting from the east coast we place much higher 
weight on maintaining strong signals into Europe for as long as possible which makes the arrival angles from that relatively short atlantic path 
much more important when designing antennas  than the relatively infrequently used long path to south east asia.  so spending more on a 
good stack that covers a wide range of angles toward Europe is much more important than trying to cover all the angles on the opposite path.  

this is what leads to designs like mine where on 10/15/20m I have 2 fixed antennas in the middle of the stack at Europe with one
rotateable one above and one rotateable one below them.  this lets me use the top antenna separately for low angle paths, and have a similar rotateable 
low antenna for high angle paths.  a separate fixed south antenna provides a quick switch when needed for carribean/south America stuff without having
to turn one of the other antennas away from Europe.  so during the day the normal running configuration is 4 antennas at Europe, then when Europe slows
down the top one is normally turned to the pacific.  it also gives flexibility for stateside contests by using the south antenna along with the low rotateable 
antenna and the top antenna, the low one is usually pointed south west and the high one west to cover the longer west coast path.

you can never have too many antenna options.

Aug 1, 2013 02:20:08 PM, xdavid at cis-broadband.com wrote:


If I remember correctly, Dean Straw said that the ARRL crunched the 
numbers back in the mid-90's using a computer that took a few days, but 
I'm not sure it really matters. We're talking optimum takeoff/arrival 
angles here, and I'm not sure that angle is a strong function of F-layer 
densities. It would be pretty easy to check ... just run a few paths in 
VOACAP for the same hour of the day using two different SSNs and compare 
the TANGLE results for various frequencies.

73,
Dave AB7E



On 7/31/2013 8:42 PM, Roger wrote:
> But is average really average. The sunspot cycles highs and lows we 
> have recently experienced are quite different than previous cycles and 
> so far this is reportedly, the lowest in a hundred years.
> From what cycle are the averages taken, or is the information updated 
> to reflect current cycles?
>
> I don't remember 40 ever being consistently as good for DX throughout 
> the nights as it was for 4 or 5 recent years.
>
> 73
>
> Roger (K8RI)
>
> _______________________________________________
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