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ARRL Propagation Bulletin ARLP004 (2011)

ARLP004 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 4  ARLP004
From Tad Cook, K7RA
Seattle, WA  January 28, 2011
To all radio amateurs 

ARLP004 Propagation de K7RA

Average daily sunspot numbers rose over the past week (ending
January 26) by 11.3 points to 32.6, compared to the previous week.
Average daily solar flux rose 3.1 points to 83.5.  Planetary A index
average was down two points to 2.9, and mid-latitude A index was
down 1.5 points to 2.4.

On Thursday, January 27 the sunspot number was 0, but a new spot is
emerging near the horizon in the southeast quadrant.

The latest prediction from NOAA/USAF shows lower solar activity,
with solar flux for January 28 at 79, then 80 for January 29 through
February 6, and 82 for February 7-22, and 88 on February 23.  This
forecast is from Thursday, January 27 and is much more optimistic
than the Wednesday forecast, which was reported in the ARRL Letter.

NOAA/USAF shows a planetary A index of 5 on January 28 through
February 2, then 8 on February 3, 12 on February 4, and 8 on
February 5.

Geophysical Institute Prague sees quiet conditions January 28
through February 1, quiet to unsettled February 2 and unsettled
February 3.

This weekend is the CQ World Wide 160-Meter CW Contest, and
geomagnetic conditions look stable, which is a favorable condition
for this contest.

Ron McCollum, W7GTF sent an image of the cover of the March, 1956
issue of CQ Magazine, which has a picture of a solar disc with
sunspots, and the headline, "Sunspot Report: ONCE IN A LIFETIME
CONDITIONS - CQ EXCLUSIVE."  Of course, as we know, after this
magazine appeared on newsstands 55 years ago, conditions got even
better over the next couple of years.

Ron wrote, "While cleaning out our family home (of 41 years) in
Seattle in preparation to sell, and to finally get rid of nearly 50
years of radio magazines, I kept this CQ."  What makes me nervous
though is his statement "to finally get rid of."

Seattle has a very convenient and efficient recycling system that
includes curbside pickup, which may make disposal a little too
convenient. I certainly hope he found a good home for these
journals.  After all, they aren't making any more of them.  Most of
the great old issues of QST from the 1920s and 1930s disappeared in
World War II paper drives.

While not related to amateur radio or propagation, Dick Bingham,
W7WKR, who lives far off the grid at Stehekin, Washington (his
station location listed in the FCC database is "1.2 miles up Company
Creek Road!") sent in a useful, interesting and educational URL (see linking to a 15-part series on
mathematics by Dr. Steven Strogatz that appeared last year in the
New York Times. This series focuses on a practical understanding of
a wide range of mathematics for lay people, such as myself.

STEREO coverage, for all practical purposes, now displays the entire
Sun.  It recently passed 99.7%, and by February 1 will surpass 99.8%
coverage.  At you can only see a narrow
slit of darkness on the Sun's far side, and on Friday morning the
new emerging sunspot region shows as a bright white area just this
side of -90 degrees longitude in our Sun's southern hemisphere.

NW7US has a page on "De-mystifying HF Radio Propagation and
Modeling" at
Here you can find some examples of coverage maps, which we showed
how to generate at in last
week's Propagation Forecast Bulletin ARLP003.

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 January 20 through 26 were 32, 42, 36, 38, 28,
27, and 25, with a mean of 32.6. 10.7 cm flux was 82.3, 87.5, 87.7,
84.3, 82.5, 80.5 and 80 with a mean of 83.5. Estimated planetary A
indices were 3, 3, 2, 2, 3, 4 and 3 with a mean of 2.9. Estimated
mid-latitude A indices were 4, 2, 3, 1, 2, 3 and 2 with a mean of


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