Topband: 160 Meter Propagation

[Bill Tippett]

W4ZV:
>         DXAID is a very useful program...it calculates a great circle map
>for any QTH and will superimpose the solar greyline for any time or date.
>You can also superimpose the auroral zone for any value of the K-index.

W7IUV:
>Interesting. I wonder how it calculates the zone. If I can believe the 
>satellite data at all, the auroral zone is usually oval shape and 
>frequently irregular at that. Also, seldom centered on the pole. Tough 
>thing to calculate. I already have a number of tools which do everything 
>except the auroral zone. Would be a nice thing to add to the collection.

        The auroral zone is an oval shaped doughnut which I believe is
centered on Magnetic North (approximately 75.7 N and 100.25 W) not the
geographic North Pole.  An interesting thing about it is that it is a
doughnut shape and not a solid oval.  This explains why some of the best
areas for viewing aurora are at latitudes south of the Magnetic North Pole.
For example Fairbanks is better than Point Barrow in Alaska.  It may
also explain why stations inside the doughnut sometimes have better
propagation than stations farther south.  Examples from recent memory
are UA1OT in FJL who used to have a tremendous signal all across NA
when few othere EU were coming through.  Another example was KL7Y's
activity from Point Barrow when he ran Europeans that stations in 
Fairbanks and Anchorage could not hear.  One simple explanation I've
heard is that the signal only had to traverse one area of auroral absorption
rather than two as stations further south would have to do.  Also, crossing
the auroral zone directly rather than obliquely means less absorption since
the signal spends less time in the high absorption area of the oval.

        If you want details on the program, please contact Peter Oldfield. 

W7IUV:
>For those same K numbers, what does DXAID show for the Phoenix to JA path 
>and the JA to EU path?

        Nowhere close on the JA path.  The western edge is around 338
degrees from AZ and JA bearing is about 310 degrees.  Tokyo to Greenwich
just touches the edge at a bearing of about 335 degrees.  

W7IUV:
>As an aside, last night, five minutes after I posted my prediction that I 
>would not hear any EU because of the auroral data I saw on the satellite 
>image, I started hearing DF2PY. I was never able to copy well enough to 
>attempt a QSO, but N7DD, about 100 miles south of me, was able to make it. 
>Later I could almost copy HA5JI. This was the best EU "opening" this year.

        Never say never on Topband...I once worked SM6CPY from Colorado
when the K-index was 8!  The signal was skewed from the normal 35 degree
bearing to 110 degrees and he reported I was also skewed over South America.
However, these were two well equipped stations and he was the only signal
I heard from Europe.  Of course you will probably not hear weaker more
distant stations in conditions like that.  From Western NA, you will find
the best conditions to Europe are when the K-index is very low...at least
that's what I saw in my 9 years from Colorado.

                                                        73,  Bill  W4ZV


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