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ARRL Propagation Bulletin ARLP039 (2004)

ARLP039 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
From Tad Cook, K7RA
Seattle, WA  September 24, 2004
To all radio amateurs 

ARLP039 Propagation de K7RA

Fall is here--time for better HF conditions. But this week sunspot
and solar flux values are down. We went from a daily average sunspot
number of 77.6 for the week of September 9-15, to 52 during the week
of September 16-22. Average daily solar flux also dropped from 119.1
to 101.1 over the same two weeks. Solar flux is expected to remain
around 90 for September 24-28, and then rise to 100 by October 1.
Geomagnetic activity should remain low over the same period, with
planetary A indices in the single digits until October 4, when we
may see a rise in activity due to returning solar wind.

More mail is coming in regarding 10-meters. At the peak of the
cycle, 10-meters sees plenty of activity, but now that conditions
are not as good on a daily basis, the band can be open but nobody
knows it unless they call CQ and someone answers, or they tune in
the beacon stations.

Donald Anderson, WK6Q of Paradise California wrote about a 10-meter
opening last Friday and Saturday, September 17-18. Paradise is in
Northern California, north of Oroville and east of Chico. At 2355z
on Friday, he worked KB3KTR in Pennsylvania with a 5-7. Then a few
minutes later at 0005z he worked KB4TWJ in Georgia with 5-9 signals,
and the next day (local time) at 1950-1956z he worked LW1DDC in
Argentina with S9 signals followed by CE2WJP in Chile running only
five watts. Throughout the day he worked a number of stations around
the U.S. and in Latin America, followed by Japan.  It was a great

Listen to those beacons. If you don't hear activity on the band but
you hear beacons from some direction that sounds interesting, put
out a CQ. There might be others tuning 10-meters but changing bands
or turning off the radio if they don't hear anything. Bo Anderson,
OZ4B who is west of Copenhagen Denmark suggests this for 12 and
10-meters. He also knows the bands are open at times when nobody
seems to be on.

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 September 16 through 22 were 80, 76, 50, 42, 59,
33 and 24 with a mean of 52. 10.7 cm flux was 108.3, 104.5, 102.7,
105.2, 100.5, 94.9 and 91.4, with a mean of 101.1. Estimated
planetary A indices were 17, 20, 16, 5, 13, 9 and 16, with a mean of
13.7. Estimated mid-latitude A indices were 14, 15, 16, 4, 8, 6 and
12, with a mean of 10.7.


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