ARRL

ARRL Propagation Bulletin ARLP002 (2007)

SB PROP @ ARL $ARLP002
ARLP002 Propagation de K7RA

ZCZC AP02
QST de W1AW  
Propagation Forecast Bulletin 2  ARLP002
From Tad Cook, K7RA
Seattle, WA  January 12, 2007
To all radio amateurs 

SB PROP ARL ARLP002
ARLP002 Propagation de K7RA

Average daily sunspot numbers for the week more than doubled from
the previous seven days, rising 24 points to 43.4. This is a nice
number for what should be the bottom of the sunspot cycle.

Gene Hastings, W1VRK of Marblehead, Massachusetts has kept a regular
weekly 20 meter phone QSO with G3LMH for over 40 years. Last Friday,
January 5 at 1400z, the signals were unusually strong, surprising
both operators. Gene said signals of late have been running about
S3, so this was a welcome change.

If we compare conditions a week earlier, using a propagation
forecasting program, with zero sunspots on December 29, 20 meters
was likely just opening over that path at that time, and the chances
of them working on the next higher band, 17 meters, would be nil.

But a week later, with sunspot numbers for Thursday through Saturday
of 36, 43 and 47, the band would open at least 90 minutes earlier,
and 17 meters would be open as well. What if a year from today the
sunspot numbers over several days were running around 80? He could
expect the band to be open all day, with the opening about two hours
prior to his regular schedule. Also, 17, 15 and even 12 meters would
likely be open, and a good chance of working G3LMH on 10 meters as
well an hour or two later.

Currently sunspots 930 and 937 are disappearing off the visible
solar disk. Sunspot numbers should be lower over the next few days,
but geomagnetic conditions should be stable. We probably won't see
unsettled to active geomagnetic conditions until January 16-17, and
later a bit more active around January 30. Sunspot numbers and solar
flux should run higher again from January 27 through February 7.

If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL
Technical Information Service at,
http://www.arrl.org/tis/info/propagation.html. For a detailed
explanation of the numbers used in this bulletin see,
http://www.arrl.org/tis/info/k9la-prop.html. An archive of past
propagation bulletins is at, http://www.arrl.org/w1aw/prop/. Monthly
propagation charts between four USA regions and twelve overseas
locations are at, http://www.arrl.org/qst/propcharts/.

Sunspot numbers for January 4 through 10 were 36, 43, 47, 46, 52, 41
and 39 with a mean of 43.4. 10.7 cm flux was 89.4, 89.4, 87.3, 86.7,
88, 92.2, and 86.2, with a mean of 88.5. Estimated planetary A
indices were 16, 9, 3, 2, 4, 4 and 7 with a mean of 6.4. Estimated
mid-latitude A indices were 13, 6, 2, 1, 2, 3 and 4, with a mean of
4.4.
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/EX