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ARRL Propagation Bulletin ARLP007 (2006)

ARLP007 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 7  ARLP007
From Tad Cook, K7RA
Seattle, WA  February 17, 2006
To all radio amateurs 

ARLP007 Propagation de K7RA

Average daily sunspot numbers this week rose over 7 points to 9, but
this doesn't mean much. Check out to see how many days
with a blank sun were noted over the last thirty days. Plan on
seeing even longer stretches of 0 sunspots over the next year. A
couple of years from now we should see a new cycle 24 rising faster
than this old one declined.

Check out a great website showing sketches of sunspots drawn in 1612
by Galileo Galilei, The
coolest part is the arrangement of the sketches into a sort of
flip-book animation, which you can view with any media player such
as Windows Media Player or Apple QuickTime. This gives us a
reproduction of what the sun was doing over the 35 days that Galileo
made these sketches. What a remarkable thing.

The ARRL International DX CW Contest is on for this weekend.
Sunspot 854 is pointing straight at us, but it is tiny. For an idea
of the relative area covered by this spot, check the web site
mentioned in the first paragraph above, and look at the Sunspot Area
shown in the fourth column, relative to sunspot area in January.

Look for sunspot numbers and solar flux to rise only slightly, if at
all, and for quiet geomagnetic conditions. Sunday, February 19
should give us only slightly unsettled geomagnetic conditions.
Based on the previous solar rotation, Wednesday, February 22 looks
like it may show some fairly active geomagnetic conditions.

Geophysical Institute Prague predicts slightly different conditions,
with February 19 unsettled to active, and February 21 and 22 just
unsettled. They think today and tomorrow, February 17 and 18, will
be quiet. They predict quiet to unsettled conditions for February 20
and 23.

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 and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at, An archive of past
propagation bulletins is found at,

Sunspot numbers for February 9 through 15 were 24, 13, 11, 0, 0, 0
and 15 with a mean of 9. 10.7 cm flux was 74.8, 75.2, 76, 76, 76.3,
77.3, and 78.5, with a mean of 76.3. Estimated planetary A indices
were 2, 2, 6, 3, 2, 1 and 12 with a mean of 4. Estimated
mid-latitude A indices were 2, 2, 4, 2, 2, 1 and 7, with a mean of


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