ARRL

ARRL Propagation Bulletin ARLP006 (2004)

SB PROP @ ARL $ARLP006
ARLP006 Propagation de K7RA

ZCZC AP06
QST de W1AW  
Propagation Forecast Bulletin 6  ARLP006
From Tad Cook, K7RA
Seattle, WA  February 6, 2004
To all radio amateurs 

SB PROP ARL ARLP006
ARLP006 Propagation de K7RA

Sunspots are back in view. Last week's Propagation Forecast Bulletin
ARLP005 reported two days with a sunspot number of 0, but this week
the average daily sunspot number rose 28 points to 66.7. This is
nice for short term HF propagation, but now that January has passed,
a look at monthly averages shows a clear decline in the sunspot
cycle.

The monthly average of daily sunspot numbers in January 2003 through
January 2004 were 150.0, 87.9, 119.7, 114.3, 89.6, 118.4, 132.8,
114.3, 82.6, 118.9, 103, 75.7 and 62.3. Average daily solar flux
values over the same months were 144, 124.5, 133.5, 126.8, 116.6,
129.4, 127.7, 122.1, 112.2, 155.5, 140.8, 116.1 and 114.1.

You can see that over the past 13 months average daily sunspot
numbers dipped below 100 several times, but were never below 82.6
until December and January when they dropped to 75.7 and 62.3. Look
for declining solar activity over the next few years, with the
predicted bottom of the solar cycle still three years off.

Right now sunspot 551 is moving into the center of the visible solar
disk, the place where sunspots have the most effect on earth.
Geomagnetic conditions at mid-day today (Friday, February 6) were
unsettled, but unless the active region around sunspot 551 spews
forth, conditions should be normal over the next few days. The
predicted solar flux over this weekend (February 6-9) is 105-110.
Solar flux values should peak around 130 toward the middle of the
month.

This week let's look at paths to Brazil, where it is currently late
summer. We will look at 20 meters and above only.

From Dallas Texas, check 20 meters 1230-1400z and 1800-0730z.
Signals may be strongest around 2230-0200z. 17 meters looks good at
most times from 1300-0100z, best from 2000-0100z. 15 meters looks
great from 1330-0000z, and 12 meters 1400-2330z. Check 10 meters
from 1430-2230z.

From Cleveland Ohio, check 20 meters around 0700-0800z 1230-1400z
and 1800-0200z. Best conditions should be around 2130-0030z. Check
17 meters from 1230-0000z, best around 1230-1300z and 1930-2300z.
15 meters is promising 1300-2300z, 12 meters 1330-2130z and 10
meters 1430-2030z.

From Boston Massachusetts, check 20 meters 0630-0730z and
1100-0200z, best around 2100-0000z. 17 meters should work from
1200-2330z, best around 1200-1300z and 1900-2230z. Check 15 meters
1230-2230z, 12 meters 1300-2100z and 10 meters 1400-2000z.

From Atlanta Georgia, check 20 meters 1230-1400z and 2000-0200z,
best from 2130-0030z. Check 17 meters 1230-0000z, best 1230-1330z
and 1900-2330z. 15 meters should work from 1300-2300z, 12 meters
1330-2330z and 10 meters 1430-2130z.

From Salt Lake City Utah, check 20 meters around 1330-1400z and
2130-0230z. 17 meters should work 1430-0100z, with the weakest
signals around 1600z and strongest later in the period. 15 meters
looks good from 1500-0000z, 12 meters 1530-2230z and 10 meters
1630-2130z.

From California, 20 meters 2300-0800z, 17 meters 1830-0200z, 15
meters 1500-0100z, 12 meters 1530-0000z and 10 meters 1630-2300z.

From the center of the continental U.S. (in Kansas), 20 meters
2000-0130z, 17 meters 1400-0000z, 15 meters 1430-2230z, 12 meters
1530-2130z and 10 meters 1630-2000z.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the Propagation page on the
ARRL Web site at http://www.arrl.org/tis/info/propagation.html .

Sunspot numbers for January 29 through February 4 were 25, 42, 49,
57, 106, 103 and 85 with a mean of 66.7. 10.7 cm flux was 87.4,
92.7, 94.4, 97.3, 101.5, 99.4 and 101.4, with a mean of 96.3.
Estimated planetary A indices were 10, 17, 12, 11, 21, 17 and 15,
with a mean of 14.7.
NNNN
/EX