KL7Y wrote:
>Skew path on 160 is not real common here; the rarity makes it difficult
>to examine. On other bands the same skew paths seem much more common.
>As an example, in last years's WW CW I worked dozens of stations on 40
>beaming a skew heading of approximately 235 degrees. The stations
>ranged from UN (normal SP heading 330) to EA (26 degrees). With a 3 el
>beam, there was no doubt about the heading - it was just a tad north of
>SW. True Long Path is out of the question as all long paths would have
>had to cross well into the sunlit South Polar region and none of the
>LPs' bearings were close to 235.
Dan, you've just described what most west coast folks commonly
call "long path" on the low bands. For whatever reason, it usually is
around 210 degrees instead of 235 at lower latitudes but that may be a
function of your latitude above 60 degrees North. The bearing is amazingly
consistent and on 80 meters, I worked stations from approximately the same
range of normal headings as you did (almost 50 different countries ranging
from 30 degrees to 330 degrees true)...all at a bearing of 210 degrees.
This bearing has been confirmed for years by people like K6UA and W6RJ who
use rotary antennas on 75/80.
>This occurence provided some more information:
>
>1. Despite a 56 degree difference in normal heading, every station came
>from 235 degrees. There was no difference in heading despite the large
>separations on the other end.
Correct...amazingly consistent and independent of "true" long path
bearings.
>2. The only station worked who was near the terminator at this time was
>a lone ZS, all the others were at least a couple of hours into darkness.
In my 80M experience, the path is optimum at 20 minutes before local
sunrise and 20 minutes after local sunset at the other end, but I recall
seeing the path at >1 hour before local sunrise and 2 hours past local
sunset at the far end. This last case was with RV0YF in Zone 23 whose
true bearing was ~340 degrees from Colorado. If you want to send me
typical QSO data, I'll be happy to run a DX-Aid plot and post it for all.
>3. The path closed at my dawn. Under normal conditions, the short path
>would have remained open for at least a couple of more hours.
Agree. Another phenomena is that the azimuth will switch from
210 degrees to direct (for stations at a bearing of 330-359 degrees) as
sunrise approaches. I even noticed this on XZ0A on 160 a few times.
As my sunrise approached, his signal shifted from the 210 degree path to
a northwestly path and the signal became weaker.
>4. JAs were coming in also, but on normal heading (270). The area that
>did the skewing was evidently farther away than the 2 hops to JA.
Same for me from Colorado. I NEVER recall hearing JA's on 160
other than the direct 315 degree path to JA. Only stations between 330
and 30 true could be worked on the 210 degree path.
>5. Signals were weak and messy with some flutter or multipath. They
>sounded like they had gone a long way.
Yes...it's hard to describe but very characteristic on both 80
and 160. Unfortunately on 160 they are so weak that it is usually hard
to hear those characteristics but on 80 they are very distinctive.
>6. An aurora was underway at the time and it blocked the over-the-pole
>short path entirely.
I have never seen much correlation with geomagnetic disturbances
on this path which makes me think it is not related to the normal skewing
seen with a geomagnetic disturbance. I recall XZ0A coming in consistently,
day after day, with little apparent influence from the Kp index. The 80M
path is also amazingly consistent. If you listen to K6UA and the dawn
patrol on 75M, it is a rare day that they do NOT work someone on this path.
>7. I hear this path often on 40, this time was unusual in that I could
>easily work stations - normally it is tough on this path..
In my experience, it is the same on 20-160, but becomes more
difficult the lower in frequency you go. If there is a good 80M opening,
it usually indicates 160 is possible. That's how I worked 3W5FM a few years
ago...he was 589 on 80M so I asked him to try 160 where he was 449.
>I realize this was on 40m, but the time and the type of signal seem to
>exactly match those few rare morning skew paths I have heard on 160.
>(Like A6, UN, VQ9.) I suspect that the same mechanism is involved.
>Somewhere out there is a big bender or big skewer!
There is too much correlation with time of day (around sunrise and
sunset) for me to believe something connected with daylight transitions is
not involved. Unlike geomagnetic skewing, which can occur at any time of
day and on any path, this path is generally independent of geomagnetic
conditions and seems to occur only for certain geographic areas within a
fixed period around their sunrise and sunset. To me that points to something
connected with daylight transitions...and no, I'm not saying the signal
follows the terminator. I don't claim to know the path the signals follow,
I only know it works and the characteristics I need to know to take
advantage of it.
73, Bill W4ZV
P.S. I posted a DX-Aid plot of N5TW's skewed QSO with VK3's at:
http://users.vnet.net/btippett/n5tw.htm
"This plot shows the path N5TW experienced to VK3 during a geomagnetic
disturbance (Kp = 5) on 26 September 2001. Instead of the usual direct
path of 243 degrees, signals were skewed to the Northwest. During
geomagnetic disturbances, it is quite common for signals to skew away from
the auroral zone closest to the signal path...in this case skew was to the
north. Had the path been to Europe, signals would have skewed to the
south. The amount of angle skew is roughly proportional to the Kp index.
For Kp of 0-2, there is little noticeable skew but I've experienced almost
90 degrees when Kp was 8 (a path from Colorado to Sweden when signals were
skewed to a 110 degree path from the direct 25 degree path).
|