Nice explanation Frank. You hit the nail right on the head. Thanks!
John, W8FJ...
-----Original Message-----
From: donovanf <donovanf@starpower.net>
To: cq-contest <cq-contest@contesting.com>; pvrc <pvrc@mailman.qth.com>
Cc: ve9aa <ve9aa@nbnet.nb.ca>; Tim Shoppa <tshoppa@wmata.com>
Sent: Tue, Nov 29, 2016 1:51 pm
Subject: Re: [CQ-Contest] 40M open early for DX in CQWWCW
Hi Tim,
Congratulations, you've discovered some of the affects of low
sunspot activity on DX contesting strategy. During the CQWW
CW Contest those affects were compounded by the Earth
directed affects of an unusually large and energetic solar coronal
hole.
One of the most pronounced phenomena of the night time
ionosphere during fall and winter is the "mid-latitude trough"
(Google that term for more detail). Its a region of significantly
depleted total electron content (much reduced MUF) just
southward of the northern hemisphere auroral zone. The
trough occurs during about half of the fall and winter nights,
and it strongly affects propagation on high latitude paths such
as the short path from eastern north America to Europe and
Japan. During about half of those fall and winter nights (those
nights when the trough is active), the trough typically develops
near sunset at its westward end and rapidly disappears at
sunrise at its eastern end.
http://www.qsl.net/kl7j/images/latitude%20variations.jpg
Last weekend the night time auroral zone was pushed significantly
southward by the affects of an unusually large and energetic
earth-directed coronal hole that also pushed the mid-latitude
trough directly over our north- Atlantic propagation paths to Europe
and our high latitude short path to Japan. As a result, our best 40
meter propagation to Europe occurred during north American
daylight hours and after European sunrise. The mid-latitude
trough significantly shortens the duration of 40 meter propagation
to Europe and Japan for stations located at more northerly
latitudes and somewhat less for stations at more southerly
latitudes during those nights when the trough is active.
Our very brief short path propagation from the mid-Atlantic
states to Japan occurred near JA sunset (0730-0830Z). Soon
after JA sunset our propagation to Japan was mostly via the skew
path that propagates via the tilted ionosphere about 20 degrees
south of the equator, Our east coast short path to Japan usually
strongly redevelops near east coast sunrise, but the affects of the
coronal hole significantly degraded our short path to JA.
While the most pronounced affects of the trough are on 40 meter
propagation, it also significantly shortens the duration of our
openings to Europe and Japan on the higher bands, essentially
terminating the openings near sunset at the eastern end of the
paths during about half of the November through February nights
when the trough is active.
I ts a big mistake to consider 40 meters to be mostly a night time
DX band near the bottom of the sunspot cycle. Daytime 40
meter DX is significantly enhanced near the bottom of the
sunspot cycle by the reduced daytime E-layer MUF which
otherwise blankets the F layer during most daylight hours nearer
the top of the sunspot cycle. As a result, DX propagation is
possible on 40 meters during most daylight hours , especially for
stations located at higher latitudes from November through early
February. During those months daytime propagation is common
from the northern east coast USA to northern Europe even at
high noon.
Close to the bottom of the sunspot cycle, both the short and long
paths are strongly open from the East coast to Japan on 40 meters
during many December and early January late afternoons from
2130Z to about 2215Z. If you have a directive antenna, some
JA stations can be worked on only one of those paths if they're
also using a directive antenna. Without a directive antenna,
some JA signals can be an unreadable blur of overlapping echos.
True long paths from the USA to Japan (not skew paths) rarely
exhibit scintillation affects that are usually observed on the short
path because the long path propagates well away from the
southern auroral zone during the southern latitude summer.
73
Frank
W3LPL
----- Original Message -----
From: "Tim Shoppa" <tshoppa@wmata.com>
To: ve9aa@nbnet.nb.ca, cq-contest@contesting.com
Sent: Tuesday, November 29, 2016 2:12:10 PM
Subject: [CQ-Contest] 40M open early for DX in CQWWCW
Mike VE9AA -
You asked several good questions in CQ-Contest.
Below are some of my thoughts on the ebb and flow of band choices in CQWW:
>From the EU point of view, they can work most of the other EU's on 40M and 80M
>and 160M for points and mults. Here in NA, VE's only work W's and W's only
>work VE's for points. And even that is lopsided because the VE's have a lot
>more W's to work than W's have VE's to work.
So the EU's are on 40M even before THEIR sunset. And it is that it is often
advantageous (point wise) for a VE station to stay on 20M much later than a W,
because the VE can run W's on 20M for points.
The disturbed conditions on 40M after my sundown, caused a lot of us W1-W4's to
figure out that it was much easier to go to 40M to work EU's way before our
sundown rather than after. Also, because there was no chance of folks like me
running JA on 15M like in solar max, we were not spending a lot of time running
on 15M in the afternoon.
The usual thought that 40M is a "darkness band" is not true, even in
undisturbed conditions. It's very often for me to CQ on 40M in CWOps at 1300Z
and get replies from VK's, even though both ends are in sunlight :).
Occasionally I will be CQ'ing at 1300Z in the deepest of winter, and be picked
up by skimmers in EU (especially GW8IZR who has the most incredible skimmer
ears, maybe only met by that VK4 skimmer) even though it is local noon in EU.
I had a handful of long-path JA callers on 40M in my afternoon while I thought
I was CQ'ing for EU. The long path JA's sounded especially clear and unwobbly
to me. Both ends were in sunlight. Usually I don't get long path JA callers
until we are closer to winter solstice.
I had a VERY HARD TIME running EU on either 40M or 80M, but no problem at all
on 20M. This poor conditions on 40M/80M were very unusual for me. I'm guessing
that 80% of my 20M QSO's were running, and that 80% of my 40M QSO's were S&P.,
and that's just unusual for me.
Mike, you also asked why the EU's weren't chasing us on the skimmer spots. A
very knowledgeable local shared with me, that in poor conditions the pipsqueak
EU's who might chase skimmer spots rather than CQ, they don't stay up late
working 40M, they're in bed, so there are many fewer to reply to my CQ's even
if we could hear other.
Tim N3QE
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