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ARRL Propagation Bulletin ARLP033 (2011)

ARLP033 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 33  ARLP033
From Tad Cook, K7RA
Seattle, WA  August 19, 2011
To all radio amateurs 

ARLP033 Propagation de K7RA

Solar activity was down again this week, and the sunspot number on
Sunday, August 14, went all the way to zero, for the first time
since January 27, which was 29 weeks ago.

Average daily sunspot numbers declined nearly 50 points, to 25.6,
and average daily solar flux was down nearly 16 points to 88.5.

The latest prediction from NOAA/USAF on August 18 has solar flux at
98 on August 19, 100 on August 20-22, 105 on August 23-25, then 110
and 115, on August 26-27, then 110 on August 28-31.  Solar flux is
expected to bottom out at 90 on September 8-12.

Predicted planetary A index is 5 on August 19-20, 8 and 12 on August
21-22, 5 on August 23-25, 10, 10 and 8 on August 26-28, and 5 again
on August 29 to September 2.

Geophysical Institute Prague predicts quiet conditions on August
19-20, unsettled August 21, quiet to unsettled August 22-24, and
quiet again on August 25.

Thanks to Max White, M0VNG of Worcester, England for sending along
this story from NASA, "Solar Flares:  What does it take to be

Max and several other readers, including Douglas Schauer sent in
some articles about using helioseismology to predict the appearance
of sunspots.  See ,,, and

One of the best articles on this subject is from astronomer Phil
Plait's blog.  Read it at

Also, don't miss this video about coronal mass ejections tracked by
STEREO craft, posted by Tomas Hood, NW7US, Propagation Editor at CQ

Brad Miskimen, N5LUL of Amarillo, Texas was in the Ten-Ten
International QSO Party (a ten meter phone contest) on the evening
of August 5 working stations in Florida, Georgia, Tennessee,
Delaware and North Caroline, most S9, and some as much as 40 db over
S9, when suddenly at 0244z, "the door slammed shut.  I have never
seen/heard everyone disappear within 10 seconds.  But that's what I
experienced.  Total silence!"

If we check we
see that geomagnetic indices show a great deal of activity right
around that time, with the planetary K index reaching 8, just one
point below the maximum K index, which is 9.  Checking for that day and the next (use the
archives feature in the upper right) shows that a CME strike on
August 5 "sparked one of the strongest geomagnetic storms in years".

Dan Soderlund, KB0EO of Northfield, Minnesota wrote, "I was
operating off and on all day Saturday August 13 on 17 meters.  Late
in the afternoon (around 2200 UTC), I had my antenna pointed toward
Europe and was working hams in western EU.  All of a sudden, I
started getting JAs calling off the back of the antenna.  I turned
the antenna toward JA and made about 40 QSOs with Japan - all
stations at least S6 and most were S9 plus.  This lasted for about
an hour and then the propagation just vanished.  The interesting
thing was propagation was equally good to EU and JA simultaneously,
covering 2/3 of the earth for an hour".

Of course, propagation varies seasonally, and a small amount from
day to day and week to week, but it looks like having propagation to
Europe and Asia from Dan's location is not uncommon.  I averaged the
sunspot number for August 11-13 (32), and ran W6ELprop from Dan's
QTH (44.45 N. 93.3 W) to Japan and it shows good signals on 17
meters from 2030-0230z.  Doing the same for England shows about 10
db louder than Japan, but a rating showing less chance of
propagation over that path.  It shows a very good path from
1630-2030z, but after that it changes to a C rating, which means
25-50% chance instead of 50-75%, which is what it
shows to Japan.  Germany and Czech Republic don't look as good
during that period. It seems that propagation would be best from
Western Europe, and the further west, the better.

Pat Hamel, W5THT of Long Beach, Mississippi is active with an
experimental license on 500 KHz.  He says that signals from
Mississippi and Louisiana were copied in Alaska around 2011z on
August 12 by Laurence Howell, KL7UK near Wasilla.  Read more about
the 600 meter project at .

If you will be in or near Estes Park, Colorado on the evening of
Thursday, August 25, you can attend a lecture on sunspots and solar
cycles at a meeting of the Estes Valley Astronomical Society.  See
details at

Note that tomorrow, August 20, the September edition of WorldRadio
online will be released.  Carl Luetzelschwab, K9LA always has an
interesting and informative column on propagation in each issue.
Check on Saturday.

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 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

The multiple websites mentioned in this bulletin can be found in
packet and internet versions of Propagation Forecast Bulletin

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 August 11 through 17 were 36, 25, 35, 0, 13, 26,
and 44, with a mean of 25.6.  10.7 cm flux was 84.2, 83.4, 83.1,
88.1, 90.4, 93, and 97.5, with a mean of 88.5.  Estimated planetary
A indices were 6, 5, 5, 9, 13, 8, and 6, with a mean of 7.4.
Estimated mid-latitude A indices were 3, 3, 4, 8, 9, 6, and 6, with
a mean of 5.6.


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