I can relate several vivid examples of skew path on the low bands, although
I believe the actual mechanism may be side or backscatter.
1. W6 long path to Eu on 80 m around 15Z in the middle of winter. We KL7's
also hear this sometimes, but in our case the true long path would be from
the south, directly over the South Pole which is in constant daylight. The
signals cannot and do not come this way, but rather more to the SW, about 45
degrees off of true.
2. VE1 to KL7 on 160 during the summer. Occasionally during the summer we
will hear and work VE1's. The path comes out of the South or Southeast,
about 90 degrees from true.
3. Europe to KL7 on 80 and 160 in the fall. On those rare occasions when
we are able to work Europe on 80 or 160 in Sept or early October, the
signals nearly always come out of the east, about 90 from true. KL7U used
to have a big dropoff to the East. In Sept he would stomp me to Europe or
Africa. I believe ON4UN confirmed this skew path on 80 by beverage
selection while KL7U used a 2 el beam. In the winter the signals usually
came directly over the pole (although not always) and I do much better on
that path.
4. VS6 to KL7 160 meters. It took me a while to finally get VS6DO - he
told me he had a high mountain in my direction. One night I heard him
really loud - out of the SW - and he came back on the first call. This was
about 75 degeres from true. I believe he also noted my signal was skewed.
5. How about a skew path with one way skip? On 75 one night, KL7U and I
are yelling at a TR8 who is an honest 57. He never hears us, just keeps
CQing. Then W6RJ (he of large 80 m beam) breaks in, curious as to who we're
yelling at. When we tell him, he says that he's beaming TR8 and can hear
nothing. Then we tell him it is a skew path out of the SE towards W6 and
South America. 'RJ swings the beam down there and, sure enough, he hears
the TR8 coming in over South America although he is weak in California. 'RJ
calls him once, the TR8 comes right back with a 58; 'RJ gives him a 33. All
the while the TR8 is holding 57 in Alaska, but he can't hear a peep from us!
This case clearly shows that there was a common reflecting area which sounds
just like backscatter on 10 or 6.
Perhaps in that case the signals were following the path of least absorption
instead of the the path of highest MUF. It is experiences like this that
lead me to believe the skew path is not the result of small deviations on
each hop adding to a large deviation after many hops, but rather one big
angle change occuring because of a side- or backscattered path being louder
than the direct one. HF backscatter radars have shown that a flat calm
ocean has minimal backscatter, with a rougher ocean being a much more
efficient scatterer. If there are waves or swells with the proper
amplitude, spacing and direction, the strength of the backscatter or side
scattered signal can be just amazing. Possibly this effect, coupled with a
low absorption path, can account for some skew path signals.
Dan KL7Y
Dan KL7Y
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