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ARRL Propagation Bulletin ARLP051 (2011)

ARLP051 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 51  ARLP051
From Tad Cook, K7RA
Seattle, WA  December 16, 2011
To all radio amateurs 

ARLP051 Propagation de K7RA

Solar activity dropped this week, with average daily sunspot numbers
declining over 39 points to 94.7.  It's been 13 weeks since the
average daily sunspot number for the week was that low or lower,
when Propagation Forecast Bulletin ARLP037 reported an average of
91.7.  The daily sunspot number has been lower than this week's
average starting December 12, when it was 70, and has since been 77,
65 and 44 through December 15.

No new sunspots emerged on December 9-12, then sunspot group 1376
appeared on December 13, and 1377 on December 14.

The latest USAF/NOAA forecast has solar flux for December 16-19 at
124, then 122 on December 20 and 120 on December 21-23. Then it
jumps to 150 on December 24-26, 140 on December 27-28, and 145 on
December 29 through January 4. It then rises to a maximum of 160 on
January 8-14, 2012.

Predicted planetary A index is 5 on December 16-25, 8 on December
26-29, 5 on December 30 through January 4, 2012, 8 on January 5-6,
then 5 on January 7-21.

Geophysical Institute Prague predicts quiet conditions December
16-18, quiet to unsettled December 19, unsettled December 20, and
quiet December 21-22.

Ed McKie, KB5GT of Yazoo City, Mississippi wrote in about a tool on for looking at past solar activity by
just entering a date.

It is at and Ed
notes that it hasn't been updated with new data as of a couple of
years back.  No word from the web master, but
perhaps it wasn't meant to be updated, only providing looks at past
sunspot activity prior to the date it was created.

By the way, for a look at Ed's fine old radios, log in at
(free) and go to Click on the photo in
the upper right for a closer look.

Propagation reports for the ARRL 10 Meter contest last weekend were
positive.  Randy Crews, W7TJ of Spokane, Washington commented,
"Conditions during the ARRL 10 Meter Contest were great as expected
with the higher solar flux. Personally I feel 10 meter propagation
has not been this good for the contest since 2002."

He noted that for 2002 and 2003, solar flux in early December was
approximately 150 and 102.  For 2010 and 2011 it was 87 and 140.
Randy noted, "What a great change!  Listening to the QSOs, it was
like we all had a new horse to ride."

Rick Cincotta, KI4FW of Arlington, Virginia noted some curious short
skip propagation last weekend.  He writes, "During the 10m contest
on the East Coast in the morning and early afternoon (both days),
when the band was opened to Europe and the US West Coast (S9+), I
could hear stations, very weakly, calling from locations nearby,
closer than the usual E-S 'doughnut' that I'm familiar with from 6M
(these guys were from eastern OH, southern NY and northern NJ, RI,
CT, NC).  They never got louder than S1, but I could make out their
call signs if I cleaned the wax out of my ears and held my breath --
so to speak.  I'm QRP, so I was only able to work a couple of them
in NY."

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at For an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at Find more good
information and tutorials on propagation at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for December 8 through 14 were 142, 116, 90, 103,
70, 77, and 65, with a mean of 94.7. 10.7 cm flux was 144.8, 143.5,
140, 134.3, 131.5, 133.1, and 132, with a mean of 137. Estimated
planetary A indices were 1, 1, 6, 4, 3, 3, and 1, with a mean of
2.7. Estimated mid-latitude A indices were 2, 3, 6, 5, 4, 5, and 2,
with a mean of 3.9.


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