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ARRL Propagation Bulletin ARLP021 (2010)

ARLP021 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 21  ARLP021
From Tad Cook, K7RA
Seattle, WA  May 28, 2010
To all radio amateurs 

ARLP021 Propagation de K7RA

This weekend is the CQ World Wide WPX CW Contest, and conditions may
be a little rough.  Our current sunspot group 1072 has reached the
Sun's western horizon and is shrinking besides, and what looked like
a possible emerging spot on Wednesday was not to be.  There is a
stiff solar wind heading toward Earth, and predicted planetary A
index for May 28-31 is 20, 20, 22 and 15.  Predicted solar flux is
73 for May 28-29, 75 for May 30 through June 3, then 80, 78, 76, 75
and 70 for June 4-8.  This prediction is from NOAA and USAF on May
27, but on May 26 they predicted a solar flux of 76, 78, 80, 82, 82,
79, 80, and 80 for May 28 through June 4.

Geophysical Institute Prague predicts a minor geomagnetic storm for
May 28, active conditions May 29, quiet to unsettled May 30,
unsettled May 31 to June 1, quiet to unsettled June 2, and quiet
conditions June 3.

The STEREO spacecrafts at currently
view about 89.5 percent of the Sun.  A month from now they will see
90.3 percent, in two months the coverage will be 91.4 percent, and
it will be 92.8 percent in three months.  Currently they see a
bright spot about 30 degrees west of the sun's eastern horizon, but
this doesn't appear to be a new sunspot group, at least not yet.

Thanks to Scott Bidstrup W7RI for the heads up on an interesting
article from Scientific American on our Sun's odd behavior and low
activity.  Read it at  Julian Moss,
G4ILO has been using WSPR (Weak Signal Propagation Reporter) to
search for marginal or unknown propagation paths.  He writes, "With
the Sporadic-E season starting I thought that I would try WSPR on
10m to spot band openings.  What has been surprising is the
consistent paths between stations in Faroe Islands and Iceland and
the UK and Western Europe.  The paths were occurring even during the
period of no sunspots and occurred when no other long distance
propagation was being reported between WSPR stations anywhere else.
I would have not expected the F2 MUF to be high enough to support
propagation at that time and that latitude.

I don't think many people have regularly tried 10m at other times so
I don't know if this has been observed before.  I haven't found any
actual activity on 10m at this time but of course OY and TF are not
in parts of the world with a lot of amateurs".

At Julian has a
nice map illustrating this on his blog.  See for details on WSPR.  At Julian has a nice description of how
WSPR works.

Bob Brown, NM7M, a true radio propagation guru passed away this week
at age 87.  See the announcement at  In addition to
teaching physics at University of California at Berkeley, he wrote
"The Little Pistol's Guide to HF Propagation".

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  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 May 20 through 26 were 12, 15, 20, 23, 17, 16,
and 11 with a mean of 16.3.  10.7 cm flux was 68.8, 70.9, 72.5,
74.5, 72.6, 73.2 and 72.4 with a mean of 72.1.  Estimated planetary
A indices were 9, 5, 4, 2, 2, 5 and 6 with a mean of 4.7.  Estimated
mid-latitude A indices were 9, 4, 2, 0, 0, 4 and 5 with a mean of


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