Fw: [TowerTalk] Take-Off Angles: N6BV's Book "All the right Angles" Reply DE K0FF

[K0FF]

Subject: Re: [TowerTalk] Take-Off Angles: N6BV's Book "All the right Angles"
Reply DE K0FF


The question was has anyone actually measured the incoming angles on HF.


I can't do it with precision on HF, but regularly measure arrival angles on
6Meters with a stacked array of four 6 elements in a 25 foot "box" and have
elevation as well as height control: 0-90 elevation , 12-85 feet height. .
Fascinating results comparing different types of propagation vs the arrival
angles. Been studying this for a few years now. Most data is directly
transferable to 10M because of both the F2 and Es type skip there as well.
On HF (20M especially)  all I can do is compare antennas at different
heights (each on different towers that are adjustable in height), and
because of the TOA characteristics of each, you can expect a huge
difference, or no difference at all depending on the takeoff angle of each,
the type of propagation and distances involved. Basically here we are
dealing with reflections at different F layer heights, but more importantly
it's just the "angle of incidence equals the angle of reflectance" rule.
Sometimes it's not just the incorrect placement of the main lobe at fault,
it's the deep notch just above it. If the wave angle arrived down that
notch, an otherwise great antenna can suffer a 30 dB penalty.
Take daytime , stateside signals and look at them first on the tribander at
50 feet, and then the monobander at 100+ feet and you see little or no
difference on the S-Meter. Comeback that night and listen to AP2's 9N's,
VU's etc at S - 5 or 6 on the monobander, and indiscernible on the
tribander. You would seriously think the coax was cut.

Referring to 6M again where the results are crisply demonstrated, a tall
antenna will be beat almost every time by a short antenna on Sporadic Es
(seems to arrive at 13-18 degrees, no matter what distance is involved). On
pure F2 propagation which seems to favor the 5 degree area or even lower,
the taller antenna wins hands down by a huge margin (measured 6 S units
already). One thing that's pretty unique to 6m is an E link into an F2
event, like TEP. Last year for example I worked several VK4 stations by this
method, and even though the distance was great, the path required a high TOA
at my end at least. Same goes for the spring and fall equinox opening to
South America.

On HF there is a multiplicity of propagation types available at any one
time, and the matter becomes very complex when world-wide contacts are
discussed. Overall, my experience is that lower antennas (therefore higher
angle TOA) will equal or even better the stacked arrays when working the
same hemisphere, all other factors being equal. The tall, or stacked array
have access to low angle not represented on the pattern of the lower mounted
(therefore high angle) antennas, and will have a shot to the opposite
hemisphere that is staggeringly better. Old timers will remember one of the
first stacked 20M arrays, at W0SYK. Bill had a pair of Telrex 6 elements on
a homebrew rotating 125 foot pole. We weenie stations would ride him hard
when we beat him in pileups to the Carib,. or South America, He just
snickered though when he was the only station even to hear the Asians over
the pole that night!

I submit that the propagation issues involved are way to complicated for any
single antenna to handle. My approach as a radio-scientist (amateur of
course) is to keep all the different antennas on separate feedlines so that
the effects of each can but compared and studied.
If I were a DXer, I would have 4 Monoband Yagis stacked and fed in phase,
one above the other with the bottom one at one wavelength and the others
stacked at least on 5/8 centers above that.
If on the otherhand I was primarily a contester, I would undoubtedly go with
stacked multiband antennas, one above the other, maybe two or three of them,
and have independent rotating controls for each.
A ragchewer, a net operator, a traffic handler, a field day enthusiast would
all chose different antennas more suitable for their needs. Just as on 2
Meters there is a big difference in design of a system for EME, M/S, Tropo.
Understanding and defining the needs at hand are the first step.
The charts showing the different arrival angles of various propagation modes
and the extremes of distances allowed per hop have been in the ARRL books
for years, but I'm afraid they have evaded being the general topic of
conversation in most QSOs.

 After studying this effect on 6M for the duration of this cycle, I will
then break up the box, and reconfigure it into a Diamond, with 2 horizontal
and 2 vertical components, and then be able to properly look into polarity
rotation.

Confused? Don't be - there is no one answer.

note; all observations mentioned were done with multiple antennas, well
distanced apart, and on a coax switch or relay box for A-B-C comparisons.
each observation was accomplished by dozens or hundreds of switching cycles
to average out any errors caused by QSB etc., before any conclusions were
drawn. There is an  assumption of reciprocity between TX and RX.

Geo>K0FF




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