[TowerTalk] Tower Height

[Pat Barthelow]

HI Rod,

Just looking further for an explanation....I did some Mini Prop  What 
ifs, and some vertical pattern launch angle examinations... here is what 
I found:

 
 
Miniprop Predictions between Tucson and France:
 
5520 miles, 38.5 degrees azimuth
 
 
F-LAYER HOPS                LAUNCH AGLE, degrees
 
4                                                     9
 
5                                                     13
 
6                                                     17
 
7                                                     21
 
8                                                     24
 
9                                                     27
 
Yagi Optimizer Plots Show the following:
 
Vertical Patterns for a 4 element 20 meter Yagi:
 
At 60 ft:
 
Main Lobe centered at about 15 degrees;
Null at 30 degrees, and 3 degrees
 
 
At 80 ft:
 
Main Lobe centered at about 12 degrees;
Null at 25 degrees, and 3 degrees
 
I was thinking of a possible launch/receive angle that might
correspond to a null in the pattern when the effective height is the
lower 60 foot value, due to the better conductivity of the ground
when wet, but don't see it, as the null is either at 25 or 30 degrees,
well above the main lobe angles at both effective heights.  Looks like
you probably have either a 5 or 6 F-layer hop path..... You might plot
6 evenly spaced segments along the 38.5 azimuth of a great circle
world map, between you and France, and see where they hit.  Those
are the  F layer locations of the bounce  (understand... this is VERY
rough)  Half way between the F layer bounces is where the earth
bouces are located.  Do this for 7 segments also, representing a 6
bounce F layer path...  See where the ground bounces hit, realizing
that sea bounces are much less lossy than land bounces.   Maybe
this will help us see the reason for such a different performance
between wet and dry from your QTH.  

73, tnx for the mind exercise...de Pat, AA6EG/N6IJ... the Contest Station 
from the Government...
aa6eg@tmx.com
 
 
 
 
 
 
 
 
 
 


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