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Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity

To: "w9ac@arrl.net" <w9ac@arrl.net>, <topband@contesting.com>
Subject: Re: Topband: Monopole Elev Pattern w.r.t. Earth Conductivity
From: Charlie Young <weeksmgr@hotmail.com>
Date: Wed, 24 Oct 2012 19:46:09 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Paul, W9AC said: <As I recall, HFTA software has an ionospheric module that 
calculates the 
predictability of arrival angle as a function of frequency, time of day, 
season, etc.  Learning that program has been on my "to do" list for a long 
time.  Perhaps others here can comment on whether the arrival angle 
information goes down to 160m in that program.
 N6BV's HFTA software does include arrival angle statistics for 160M, but I am 
not sure of how useful this data is for Topband in the real world.  The 
propagation statistics are cumulative over all conditions, times of day and 
seasons and do not allow one to specify a time, season, or solar flux.  Also, 
HFTA only analyzes horizontally polarized antennas and does not do vertical 
polarization, which also limits the usefulness on 160M.   My terrain is 
extremely rugged, with steep ground slopes on all sides of my towers.  I used 
HFTA extensively before building my first tower.  It caused me to alter my 
plans for stacking two C31XR yagis, with the top one planned for 100', because 
the software predicted the top antenna would destroy the pattern.  I ended up 
going with one C31XR at 56', and even then HFTA predicted 15 and 10M 
performance would be compromised because the antenna was too high for some 
directions on my hilltop.  I went ahead with the altered plan and sold the 
unused C
 31XR but spent the next two years proving to myself the HFTA prediction about 
15 and 10M was accurate.      The proof involved erecting two other towers and 
installing lower 10 and 15 meter antennas with equivalent gain to the C31XR and 
doing extensive A versus B testing.  Without exception, if HFTA predicted that 
30' a high antenna in a given direction would outperform an equivalent antenna 
at 56', the prediction proved true.  This usually manifested as absolute higher 
signal strength in A versus B tests.   Sometimes in a given direction HFTA 
predicted the higher antenna would be best, and this was always true as 
predicted.  After two years of testing, I moved the C31XR to 35' on a crankup 
tower and installed a 5 element 20M monobander on a 45' boom in the vacated 
position @56'.  The major improvement to DX performance from this switch was 
not on 20M as most would expect, it was on 15 and 10M because of putting the 
tribander at an optimized height for my terrain.   I am a b
 eliever in HFTA for helping analyze antenna performance on rugged terrain.  I 
just wish we could make it do verticals!  73 Charlie N8RR 
                                          
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