Hi Eric,
Thank you for explaining that! I always wondered how it was possible
that I worked such a loud 3B9C (honest S9) on 4/12/04 at 0012z on 160
SSB! Were you on that DXpedition?
I also wonder if this phenomenon of ducting would explain my JA qso's on
160 which were made 1st call through a pileup of W4 /W9 shortly after
dawn some years ago? The likelihood of my ever beating out a W4 or W9
to JA on 160 is ZERO, so some rare and unusual propagation effect was at
work.
73
Bob, KQ2M
On 2024-11-21 21:47, Eric Scace K3NA wrote:
Hi Ron —
See attached image of the twilight zones at 00:40Z today. You will
see that 3B9 is in the middle (nautical) twilight zone band… and the
twilight zones cross North America.
Having worked this path myself from 3B9, I can testify to how cool
it is. Ducting explains part of why the signal was so loud when you
heard them — ducts are very low loss conduits for signals at the
ducting frequency range. But escaping from a duct requires the signal
to encounter some less-ionized part of the floor of the duct, so that
the signal can continue down toward the earth’s surface. And the exit
point still has some refraction, so the signal may exit the duct at a
very shallow angle and travel a long way before it reaches the surface.
These thin spots are indeed spotty, transient, and move around.
When I was on 3B9, clumps of geographically-adjacent stations would
get worked — a spot corresponding to a weak spot in the duct. Some
clumps were clearly connected to each other by an added ionospheric hop
in the normal way. We could plot this clumps over time and see them
move along with the terminator… but eventually (minutes or tens of
minutes) a particular “leak” would close up. Maybe we had several
“leaks” at one time, working different spots in North America… and
sometimes no leaks at all.
So yes — spotlight propagation.
This emphasizes why it’s important for a DXpedition to be on top
band every night. Some nights will have no ducts. Others with have
leaky ducts — but the leaks will only illuminate certain patches of
North America (in this case)… and on another night different patches of
North America. To give everyone a chance, one has to be on every night.
And for the person chasing the DX, one has to be listening every night
until a leak/spot favors that person’s location.
And then, as you experienced, it’s super easy to work each other
through that low-loss path.
— Eric K3NA
On Nov 21, 2024, at 19:37, Ron Spencer via Topband
<topband@contesting.com> wrote:
Tonight (11/21) around 0040Z I saw a signal pop up on the panadapter.
Tuned to it and its 3B9/M0CFW calling CQ. 15dB or more above my noise
floor. I couldn't believe how solid and loud they were. After amp came
on line I called and worked them. During the wait time I did a quick
internet search to see if is indeed a real station. Yep.
What amazed me, and still does, is absolutely NO rbn or packet spots
during the at least 5 minutes they were on. And no other callers. Even
after I spotted them on packet and the kst chat page.
I have no explanation for this. Why no rbn spots? Why no other callers
when they were very solid for almost the whole time they were calling
CQ? Was this an example of very small spot light prop? There were
others on so its not like no one was tuning the band. Baffling.
Below is a screen shot of their signal. they are in the red area.
Received on my homebrew 8 antenna circle array with no preamp.
Perhaps someone out there has an explanation.
Ron
N4XD
Sent using https://www.zoho.com/mail/
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband
Reflector
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband
Reflector
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|