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ARRL Propagation Bulletin ARLP010 (2010)

ARLP010 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7RA
Seattle, WA  March 12, 2010
To all radio amateurs 

ARLP010 Propagation de K7RA

We experienced a bit of a scare this week when four days went by
with no sunspots.  That's right -- for the first time in three
months we saw more than a single day with a sunspot number of zero,
and that last period was back during November 23 through December 8.
Until March 6, there were just three days since then with no
sunspots, each a bit less than two weeks apart, December 25, January
6, and January 19.

On Wednesday, sunspot group 1054 emerged in the northeastern
quadrant of the visible solar disc, and just south of the center of
the field another sunspot group appeared on Thursday, number 1055.
This brought the sunspot number from 12 on Wednesday to 31 on
Thursday, March 11.  The total area covered by sunspots increased 14
times from Wednesday to Thursday.

The STEREO mission (see shows a
possible third sunspot group possibly appearing over the horizon in
a few days.  As of 0300z on March 13, 88.23% of the Sun can be
observed by STEREO, and two weeks later the coverage will expand to
about 88.42%.  90% coverage should be achieved on June 18 around
2323-2335z.  The 45 day forecast for solar flux has been shifting
over the past few days.

On March 9, it predicted solar flux for March 12-22 at 78, falling
to 75 after March 23.  On March 10 it shifted to 84 on March 12, 86
March 13-18, then 78 on March 19-22.  On March 11, the latest
available for this bulletin, it changed to 85 for March 12-15, 83 on
March 16, 81 on March 17, and 80 on March 18-19.  For the latest
forecast, check  The new daily
forecast appears some time after 2100z each day.

Current planetary A index prediction from the same source shows the
value at 5 on March 12-13 and 7 on March 14-15, then back to 5.
Geophysical Institute Prague says watch for quiet conditions March
12-13, quiet to unsettled March 14-15, unsettled March 16, and back
to quiet for March 17-18.

David Moore, a shortwave listener in Morro Bay, California regularly
sends us articles of interest to readers.  About ten days ago he
sent us this article, from "Astronomy Now"
about a project at the Royal Observatory Greenwich involving the
public in an effort to analyze solar data.  Don Kalinowski, NJ2E of
Cary, North Carolina also sent a link to this project, called "Solar
Stormwatch," at

Their idea is that there is too much data for the scientists to
observe, so they hope to use a recently popular concept called
"crowdsourcing" in which large numbers of people can expand the
observatory's capabilities.  This definitely sounds like a
fascinating endeavor for many of our readers.

Lots of reports received about good conditions for the ARRL
International SSB DX Contest last weekend.  Andy Gudas, N7TP of
Amaragosa Valley, Nevada worked all continents in a half hour on 40
meters with 100 watts and a simple wire antenna, an inverted Vee.

His log:

07:56  VK3IO  Australia   Oceania 
08:07  ZX2B   Brazil   South America 
08:10  4A2S   Mexico   North America 
08:15  CR2X   Azores   Europe 
08:21  D4C    Cape Verde  Africa 
08:25  JA1ELY Japan   Asia
Scott Bidstrup, TI3/W7RI sent a link ( to
an interesting article in "Science News" about predicting sunspot
minima by studying magnetic flows.

Jon Jones, N0JK in Kansas noted E-skip a bit early for the normal
season.  On March 9 at 2320z he worked K2EK, from EL88 in Florida,
and around 90 minutes later, at 0052z on March 10 he worked AC5O
from EL49 in Louisiana.  Jon was in his car, but using a 5/8 wave 2
meter whip.  Jon notes that March normally has the lowest occurrence
of E-skip of any month of the year.  He also reported that W0WOI in
Iowa heard the TI2NA beacon in Costa Rica about 0115z that day.
Mike Schaffer, KA3JAW in EL87 (Tampa, Florida) reports receiving TV
signals from Central America around the same time.  Around 2300z he
heard YNTC, TV2 in Nicaragua.  The strongest signals were around
2325z, and gradually faded away around 0025z

Bob Alsaker, N7HJL in Phoenix, Arizona wrote, "I received my first
license in 1960 (Novice WV6NTQ) and have been active most of the 50
years since then (except for my 'vacation' in Viet Nam) Back then
working all around the world was expected, even with modest
equipment (50 Watts or less), and minimal antennas (ground mounted
verticals with no radials!). The past few months have been a real
joy again, after what has seemed like an eternity with no sunspots
and no DX."

"The recent ARRL CW DX contest was once again a blast!  Over fifty
countries with 9 new ones added to my DXCC.  For all the hams
licensed in the past decade, get ready for some real fun, especially
if you like working DX.  Us OTs remember!"
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 a detailed
explanation of the numbers used in this bulletin, see An archive of past
propagation bulletins is at

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

Instructions for starting or ending email distribution of this
bulletin are at

Sunspot numbers for March 4 through 10 were 40, 35, 0, 0, 0, 0, and
12 with a mean of 12.4.  10.7 cm flux was 81.3, 79.5, 78.3, 76.6,
76.3, 77.9, and 80.3 with a mean of 78.6. Estimated planetary A
indices were 6, 2, 3, 4, 3, 2 and 7 with a mean of 3.9. Estimated
mid-latitude A indices were 4, 1, 3, 3, 1, 2 and 6 with a mean of


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