A response to my FT5XO posting from Al, K7CA, has led me to one of the most
fascinating examples of DX propagation from North America that I have ever
played with. I know the propagation gurus know all this stuff already, but for
the rest of us, read on --this is fun!!! Al reported:
>Hi Bud,
> I worked the FT5 at 01:42z, about 5 min before my sunset [and almost exactly
> FT5XO's sunrise]. His direction was directly NE from my Cedar City, UT QTH.
> I can tell
>direction within about 15 degrees. My antenna has a 28 degree
>azimuth beamwidth to the NE. He was peaking 579 and was not copyable
>east, southeast, or south. 73, Al K7CA
For those who haven't had time to run a lot of great circle displays from FT5X
to different geographical regions, I thought Al's report might be worth
expanding upon, and a source of hope for midwestern and western NA topbanders
the next couple of nights:
1. Subject to the limits of W6ELProp and my fingernail map interpolation
skills, the antipode of Kerguelen is near a place called Manyberries, in
southeastern Alberta, near the Saskatchewan and Montana borders. (I find this
antipode stuff fascinating because my own QTH, here in upstate NY, is the
antipode of nothing inhabitable at all!)
2. If you use a small enough map, Utah is fairly close to Manyberries, thus
"almost" the antipode of FT5XO. Consequently, there is very little difference
in mileage (about 1200 US miles) between Al's short path and his long path to
Kerguelen. I've noticed very little chatter on here about the antipodal nature
of Kerguelen for central Canada and the Rocky Mountain states, but it's worth
repeating that the closer you get to being antipodal with the DX you're
chasing, the less important the calculated or "expected" beam headings become.
The transmitted signal will go where the path loss is minimum, meaning
somewhere on the dark half of the earth on 160. Reception will be best where
the signal to noise ratio is best, and that may or may not be maximum in the
same direction, depending on local QRN, QRM, and other factors.
3. Because we happen to be near an equinox this week, K7CA's sunset and
FT5XO's sunrise are very nearly coincident. (Think "double enhancement" on the
grayline.) Three months from now, they won't be. (Nor is the FT5XO team
likely to still be on the island....)
4. Also because we are near equinox, everyone's grayline is almost exactly
north and south through their own QTH at their own sunrise and sunset. By June
it'll be tilted 22.5% (IIRC) in one direction, and by December an equal amount
in the other direction.
5. If you plug in Al's coordinates for the center of your great circle mapping
program (W6ELProp just happens to have latitude and longitude for W7 centered
on Salt Lake City pre-loaded in its Atlas), you will see that the grayline
passing through Utah at 0142Z runs about 5 degrees east of North and west of
South, or very nearly vertical -- and is almost _exactly_ lined up with Al's
short and long path headings to FT5XO. (Think "all K7CA's stars are in
alignment this week....") Al reported receiving the FT5 best on his NE
Beverage (which is very close to his so-called "long path" bearing) but because
he's so close to being antipodal with Kerguelen, conditions on any given
evening or at any given moment might have favored _any_ of his Beverages from N
through E to SE and S (i.e., the dark half of his propagation circle to FT5).
Nonetheless, the "double enhancement" of near simultaneous sunrise and sunset
for Al and his target make it highly likely that signals were best a
bout 5-15 degrees east of his North.
5. Let's contrast that with W1. At Kerguelen sunrise (0142Z), the closest
approach of the grayline to New England is over the middle of Canada -- not far
from Manyberries, AB, in fact -- but probably too far away to be of any use.
So a W1 most likely must depend on standard short path propagation to work the
FT5. Yes, there will be signal enhancement due to sunrise occurring at the FT5
end of the circuit, but _every_one at this end will benefit from that, not just
W1s. A glance at the grayline for 0142Z shows us that K7CA's competition in
working the FT5 will most likely come not from New England but from parts of
Central Asia.
6. VE3CSK reported that FT5XO peaked at his QTH just east of Detroit at 2345Z,
dropping into the noise by 2355. If you run the great circle map centered on
Bill's location you could surmise he was experiencing a sunset peak shortly
after the grayline went through his place. At 2345 FT5XO is just far enough
from the grayline and his own sunrise that it's possible Bill's QSO could be
either via conventional (!!!) short-path means or via the grayline in one
direction or the other. Bill reported best reception on his East Beverage,
which isn't that far from his 117-degree short-path heading, so I would be
inclined to tilt in favor of short path, rather than grayline. In my
experience, this is an especially interesting situation: Note that in this
particular case (with one end of the circuit not exactly on the grayline) and
Bill not being near the antipode that the two grayline paths are nearly at
right angles to the short and long paths. Thus, even without "skew" paths to
be concerned about, there are three directions to listen in (the sunny long
path clearly isn't possible on this band).
7. What about W9 and W0? Well, I have found on 40 (where I have a rotatable
antenna) that it's possible to "merge" your signal into the grayline path even
though your QTH may be an hour or more off the discrete grayline. I like to
think of it as aiming my beam as if I were going up an entrance ramp onto a
superhighway (the grayline). Consider a station in Omaha, NE, whose short-path
bearing to FT5XO is 134 degrees or SE. At 0142Z Omaha is sufficiently close to
the grayline going through Utah that I believe from minute to minute the best
strategy might be the SE path or it might be to aim a little east of north or
SW in order to "slide" into the grayline superhighway. Having the ability to
quickly switch directional receiving antennas might make the difference between
a solid QSO and a "definite maybe".
Bottom line: The midwest and west have an opportunity to be competitive with
the east coast when chasing Kerguelen this week. This is a direct result of
their being near the antipode of FT5X and it being equinox time. Go get 'em,
guys and gals.
Bud, W2RU
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