I'll make a few closing comments, as I suspect the moderator will be cutting
this off soon.
When I used 45 degrees, that was a number out of a hat for illustrative purposes
only. The point being that we hams tend to think that we can "force" the TOA to
be lower, and lower is always "better." NM7M (SK) in his book, "The Big Guns
Guide to Low-Band Propagation" mentions the case where a low angle signal (10
degrees) can't penetrate the E-layer and needs many more hops than a higher
angle signal that does penetrate and gets to the F-layer were fewer hops are
necessary to cover the same path.
Eric, KL7AJ, has a couple of thought-provoking papers in QST that have a
different take as well. They are, "Gimme and X, Gimme an O", QST, Dec. 2010,
pp 33-37 and "Three Wrong Assumptions about the Ionosphere", QST, Mar 2012, pp
40-42.
Carl, K9LA, in a presentation
(http://wwrof.org/webinar-archive/a-long-overdue-review-of-gray-line-propagation-on-the-low-bands-by-carl-luetzelschwab-k9la/)
shows an example where IONCAP says there is no (usable) path between two
stations, yet QSOs are made.
Wes
On 7/13/2016 5:48 PM, David Gilbert wrote:
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
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