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ARRL Propagation Bulletin ARLP050 (1998)

ARLP050 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 50  ARLP050
From Tad Cook, K7VVV
Seattle, WA  December 11, 1998
To all radio amateurs 

ARLP050 Propagation de K7VVV

Solar activity was lower this week, with both average solar flux and
sunspot numbers down about 10 points each when compared to the
previous week.  Average solar flux for the previous ninety days was
131, and solar flux was above this value on every day, indicating a
good general upward trend.

Solar flux peaked at 162 on Tuesday, and the trend now is downward.
For the ARRL Ten Meter Contest this weekend look for a solar flux of
132, 128 and 122 on Friday through Sunday.  Geomagnetic indices
should be unsettled to active, with the planetary A index peaking
around 15 on Saturday.

It would be nice to have a higher solar flux for the ARRL Ten Meter
Contest, but contesters can look forward to much better conditions
than last year.  Last year the Friday through Sunday solar flux for
the 1997 ARRL Ten Meter Contest was 92.5, 89.3 and 90.  This just
wasn't enough for good propagation over most paths.  Just plug the
numbers into any popular propagation prediction program, and the
predicted numbers for this weekend look great in comparison.

The general trend in solar activity has been up this year.  Take a
look at the chart at or at and see the general upward trend.
Beyond this weekend look for solar flux to drop to 120 or lower by
December 16, then rise above 130 three days later and above 140 by
December 22.  Flux values are expected to peak above 150 around
December 27.

NASA released an interesting story this week about solar wind
squeezing ions out of the ionosphere.  See the press release and
images at

Sunspot Numbers for December 3 through 9 were 136, 109, 91, 106,
143, 158 and 132 with a mean of 125.  10.7 cm flux was 153.1, 148.2,
142.4, 142.3, 153.2, 162 and 153.9, with a mean of 150.7, and
estimated planetary A indices were 7, 7, 12, 7, 6, 5 and 5, with a
mean of 7.

Here are some path projections for the ARRL Ten Meter Contest this

Look for Europe from the East Coast around 1530-1700z, South America
with strong signals around 1430-1930z, South Pacific around
1800-2200z, Hawaii around 1800-2030z, and the West Coast from

From the Central USA, look for Europe around 1600z, South America
from 1500-2100z, South Pacific at 1730-2330z, Hawaii from 1800-
2300z, Japan around 2200-2300z, the East Coast around 1800-2000z and
the West Coast from 1700-2100z.

From the West Coast, check South America around 1530-2330z, South
Pacific around 1830-0030z, Hawaii around 2000-2100z, and Japan
around 2230-0000z.


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