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

[Charlie Young]

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 C31XR 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 believer in HFTA for helping analyze antenna performance on rugged terrain.  I just wish we could make it do verticals!  73 Charlie N8RR