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ARRL Propagation Bulletin ARLP049 (2004)

ARLP049 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 49  ARLP049
From Tad Cook, K7RA
Seattle, WA  November 29, 2004
To all radio amateurs 

ARLP049 Propagation de K7RA

Because last week's bulletin was prepared Tuesday night, it didn't
include the numbers that are always at the end of this bulletin.
This is an extra bulletin put out after the Thanksgiving holiday to
catch up on those numbers.

The reporting week that we use for the data runs Thursday through
the following Wednesday, so we are reporting and comparing data from
November 18-24 with the earlier seven-day period from November
11-17. The November 18-24 data is not much different than the
earlier period. Average daily sunspot numbers are a little lower,
and so are geomagnetic indices.

Currently early Monday morning a solar wind is up against earth's
magnetic field, but so far the worst effect is a K index of 3,
indicating unsettled conditions, but not active. Conditions over the
weekend were a little rough, with both the mid-latitude and
planetary K index as high as 5.

The current forecast shows a moderate A index of 10 over the next
few days, but active geomagnetic conditions are predicted for
December 2-3. Daily solar flux values around 110 are predicted
through December 1, rising a bit higher through December 5.

The nights are longer now in the Northern Hemisphere, and will
continue to lengthen through December 21, the Winter Solstice. This
suggests an emphasis on the lower bands for communication,
especially for those of us at a higher latitude. On December 21
Miami, Florida will have 10 hours and 34 minutes from sunrise to
sunset, but Seattle, Washington will only have 8 hours and 40

Plotting a 10 meter daylight path from Miami to Brazil on the
Solstice using propagation software such as W6ELprop, shows a 4-hour
longer opening than a path from Seattle to Brazil under the same
conditions. Those in the southern states of North America frequently
have longer and better openings to the rest of the world than
operators further north.

If you would like to comment or have a tip, email the author at,

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,

Sunspot numbers for November 18 through 24 were 77, 61, 40, 27, 28,
45 and 72 with a mean of 50. 10.7 cm flux was 104, 102.2, 99.3,
100.9, 106.3, 106.9 and 107.3, with a mean of 103.8. Estimated
planetary A indices were 3, 4, 18, 16, 10, 5 and 6, with a mean of
8.9. Estimated mid-latitude A indices were 4, 3, 12, 9, 6, 4 and 7,
with a mean of 6.4.


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