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ARRL Propagation Bulletin ARLP027 (2006)

ARLP027 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 27  ARLP027
From Tad Cook, K7RA
Seattle, WA  July 7, 2006
To all radio amateurs 

ARLP027 Propagation de K7RA

Solar activity was up this week.  Average daily sunspot numbers rose
nearly 22 points from last week's average to 35.6.  Average solar
flux rose as well, 11 points from 75.7 to 86.7.  The (moderately)
active geomagnetic day this week was July 5, with a planetary A
index of 19, and the college A index from the magnetometer near
Fairbanks at 28.

The increased geomagnetic activity was due to a high-speed solar
wind stream from a coronal hole on the sun beginning July 4.  Earth
was vulnerable due to a south-pointing interplanetary magnetic field
(IMF).  When the IMF points north, Earth is less vulnerable.  The
IMF is again pointing south on July 7.  The next increase in
geomagnetic activity is predicted for July 9.  The current
prediction for the planetary A index for July 7-10 is 8, 10, 25 and
18.  Solar flux for those days is predicted at about 85.

When the solar wind stream hit earlier this week, a radio burst from
giant sunspot 898 was recorded by Thomas Ashcraft of Lamy, New
Mexico at 1743z on July 5.  He used receivers tuned to just above 17
meters and just above 15 meters to produce a binaural audio
recording best appreciated with stereo headphones.  Listen to it at  Thanks to Don
Mayhall, N5DM for the tip.

We received more notes on 6 meters and Field Day.  Bill Baker, W5GT
reports that his club entry from W5NOR in Oklahoma used a rotatable
dipole on six and made 109 contacts over June 24-25.  Bill Van
Alstyne, W5WVO of Rio Rancho, New Mexico writes of six meters on
Field Day, ''Saturday evening saw some really nice double-hop into
the east (NY, PA, MD, VA mostly), plus the usual single-hop path to
the mid-way point (MO, IA, IL).  Signal strength on the east coast
stations was very good, in some cases as good as the Midwest
stations.  Worked a new grid square (FM09) in the WV panhandle, a
club FD effort that decided to activate this somewhat rare grid as
well as work the contest.  Sunday morning featured a long, strong,
and fairly broad opening into the Midwest -- MO, IA, IL, IN. WI, MN,
and others.  Only sporadic east coast contacts, mostly in FL''.  Bill
is looking forward to the CQ World Wide VHF Contest, July 15-16.

Eric Hall, K9GY of Lansing, Illinois reminds us to operate the IARU
contest this weekend and specifically work operators in the World
Radiosport Team Championship 2006, which this time around is held in
Florianopolis, Brazil.  You can follow the progress of the teams via
an online scoreboard.  Check

If you want to work the teams in Brazil, propagation to South
America from the Northern Hemisphere should be good this weekend.
From California, best times should be 80 meters around 0330z and
0530-0900z, 40 meters 0330-1000z, 20 meters 0100-0700z, and 15
meters 1700z-0530z, with the best bet around 2330-0430z.  Although
not a sure bet, check for 10-meter openings 2000-0500z.

From Chicago, 80 meters looks best 0330-0900z, 40 meters 0130-0930z,
and 20 meters 2230-0530z.  15 meters does not look promising, but
your best bet is 2100-0400z.

From Dallas, 80 meters looks good 0230-0930z, 40 meters 0100-1000z,
20 meters 2230-0530z, 15 meters 1700-0200z, and perhaps 10 meters,
best chances 1800-0400z, with stronger signals toward the end of
that period.

From Philadelphia, 80 meters looks good 0200-0830z, 40 meters
0000-0730z, 20 meters 2200-0530z, and perhaps 15 meters from

You can work out paths from your own location using the method
outlined in earlier bulletin ARLP014.

Read it at

Of course, for the IARU contest, you work stations all over the
world, not just in Brazil.  See the IARU HF World Championship rules
on the ARRL web site at

The end of June brings to a close the second quarter of 2006.  This
is a good time to review average quarterly and monthly sunspot and
solar flux numbers.  It's a good way to spot trends.

From the first quarter of 2003 through the second quarter of 2006,
the average daily sunspot number was 120.3, 107.3, 110.2, 99.2,
72.9, 71.3, 69.3, 61, 46.1, 55.7, 58, 36, 18.1 and 39.7.

The average daily solar flux for the same period was 134.3, 124.2,
120.8, 137.4, 111.1, 99.5, 111, 104.8, 96.4, 93.1, 93.6, 84.5, 78.5
and 82.1.

Three-month averages should be a bit smoother than one-month
averages, and from the numbers above you might think we already hit
bottom on the solar cycle and began a rebound.  Although activity is
low, we haven't seen the weeks of zero sunspots that we experienced
about a decade ago during the last solar minimum.  Also, look at the
monthly numbers below.  Although there was a slight uptick in
sunspot numbers and solar flux for the last quarter, the monthly
numbers for the three months that make up this last quarter show an
orderly decline.

The average daily sunspot numbers for the months May 2005 through
June 2006 were 65.4, 59.8, 68.7, 65.6, 39.2, 13, 32.2, 62.6, 26.7,
5.3, 21.3, 55.2, 39.6 and 24.4.  Average daily solar flux for the
same months was 99.5 , 93.7, 96.5, 92.4, 91.9, 76.6, 86.3, 90.8,
83.4, 76.5, 75.5, 88.9, 80.9 and 76.5.

We now have a new forecast from NOAA Space Environment Center for
the bottom of this solar cycle, and compared to the forecast of the
past few years, it puts the bottom just slightly further out than
the forecast of a few years ago, which is all we had until this

You can see it in the charts in the back of the July 4 Preliminary
Report and Forecast, at  Note on pages 9 and
10 that the table of predicted smoothed sunspot numbers put the
minimum in January 2007, or it may be more realistic to characterize
it as occurring between December 2006 and May 2007.  The projection
running just one week earlier, at is the same one that
has been out for several years.  Note the minimum sunspot numbers at
December 2006 and January 2007.  Similar numbers for the smoothed
solar flux, which in last week's table show a minimum from December
2006 through April 2007, while this week's forecast shows January
through April 2007.  Not much difference, but a slight shift out
into 2007, and the first update to this forecast in years.

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation, see the ARRL
Technical Information Service at For a detailed
explanation of the numbers used in this bulletin, see An archive of past
propagation bulletins is at .

Sunspot numbers for June 29 through July 5 were 35, 38, 36, 34, 38,
40 and 28 with a mean of 35.6. 10.7 cm flux was 85.5, 86.1, 85.5,
87.1, 85.9, 92, and 84.7, with a mean of 86.7. Estimated planetary A
indices were 12, 8, 5, 2, 4, 13 and 19 with a mean of 9. Estimated
mid-latitude A indices were 8, 7, 3, 1, 2, 11 and 18, with a mean of


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