I've played around with VOACAP a lot in the past. Possibly you want to
argue with it's validity, but I can tell you that the percentage of time
it shows signals optimally arriving at 45 degrees is much less than the
percentage of time they arrive closer to 10 degrees ... certainly for
any kind of DX work and most of the time for domestic work here in the
U.S. That depends upon the band, of course, and also the time of the
opening (optimum angles are lower at openings and closings versus
mid-opening), but in general the best TOA's area lot lower than most
hams assume.
If low takeoff angles weren't generally desirable our hobby has several
generations of very misguided members who have squandered millions of
dollars.
Dave AB7E
On 7/13/2016 5:02 PM, Wes Stewart wrote:
Jim, I've looked at your stuff in the past.
But, "improvement" is in the eye of the beholder. The ionosphere
determines the optimum TOA, not the antenna. Taking heroic measures to
get the max TOA down to 10 degrees (a near impossibility over dirt)
when the signals are arriving at 45 degrees is hardly optimum.
Anecdotal evidence is mostly worthless but for what it's worth, I have
48 entities worked on 160 meters from here in the desert using no more
than 500 watts into an inverted-V, apex at 45' ends at 6'. Everyone
"knows" that this can't possibly work because it radiates straight
up. (Except that it doesn't)
Wes
On 7/13/2016 3:07 PM, Jim Brown wrote:
On Wed,7/13/2016 12:03 PM, Wes Stewart wrote:
Ok, but I'm unclear about what "improves radiation pattern" means.
Wes,
Take a look at the links I posted to my NEC studies. There can be no
doubt as to the meaning of "improves radiation pattern."
BTW -- I do NOT agree that elevated radials have much to do with
establishing the take-off angle. AND, more to the point, I view
take-off angle as absolutely the wrong way to look at the vertical
pattern of an antenna. A FAR better approach is the one I used in
those antenna planning applications notes, for which I posted links a
few hours ago.
73, Jim K9YC
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