Topband: 3B9/M0CFW on 160

[kq2m at kq2m.com]

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 at 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/
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