The whole concept of skewed propagation via this current thread that we
are discussing is just a matter of semantics. Also I appreciate Bill W4ZV
allowing me the time to explain the theory on this reflector.
Bob NM7M and I are really not in disagreement at all. Bob merely chooses
complex explanations that can be hard to understand. I simply choose to use
W6SAI's (SK) "KISS" method of writing and communicating. I have found that
this method works best whether it be in teaching about radio wave
propagation or Meteorology.
On my HF/MF Radio Propagation Theory Notes site at:
http://www.kn4lf.com/kn4lf8.htm I state:
7.) Propagation Path Skewing-
Basically the simplest way to look at medium frequency signal propagation
path skewing is that the transmitted RF signal will "always" seek to
propagate along the path with least absorption, which almost always means
via a darkness path. As an example a signal transmitted from Norway to New
England, which is a polar great circle path, will be directly absorbed most
of the time by the Aurora Oval, with the remaining medium frequency signal
skirting south and then west on the darkness path, arriving in New England
from say the SE rather then the expected NE path. Also medium frequency
skewed propagation paths are the norm rather then the exception, especially
past approximately 3100 miles.
In simpler terms the MF RF transmitted from Norway towards Maine in New
England that traverses the "radio" auroral oval region, usually suffers
absorption and/or unpredicatable scattering and does not arrive in Maine.
Let's call this the path of "most" resistance. As the transmitted signal
from say a 1/4 vertical, is not a narrow beam like a 300 gig laser, it has a
relatively wide horizontal beamwidth and in the vertical plane probably
radiates a signal between 90 and 15 deg., that reaches the ionosphere. Due
to the wide range of angles radiated in the horizontal and vertical planes,
some of this signal skirts south and west of the "radio" aurora oval and
arrives in Maine from the SE instead of a more expected NE direction. In a
practical sense you can say that the skewed signal arrived via the path of
"least" resistance or absorption. This is especially true if the signal
arrives via the E-Valley/F Layer duct, versus multiple refractions between
the E Layer and land/ocean surface.
A second analogy. You have a dam holding back a large volume of water. The
spillway is open
and some water is flowing through the spillway into the river below. The
water passing through the open spillway is traveling via the path of "least"
resistance. Now a great flood of water from above enters the lake behind the
dam. The lake fills up and eventually flows over the top
of the dam structure, even though the spillway is open. The water spilling
over the top of the
dam is taking the path of "most" resistance.
73,
Thomas Giella, KN4LF
EL87WX
Plant City, FL, USA
KN4LF Daily Solar Space Weather Geomagnetic Data Plus MF Propagation
Outlook:
http://www.kn4lf.com/kn4lf5.htm
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