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ARRL Propagation Bulletin ARLP024 (2011)

ARLP024 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 24  ARLP024
From Tad Cook, K7RA
Seattle, WA  June 17, 2011
To all radio amateurs 

ARLP024 Propagation de K7RA

The average daily sunspot number for the past week declined by more
than half, nearly 52 points to 35.1, when compared to the previous
week.  Average daily solar flux declined nearly 12 points to 90.1.
Note that from Wednesday (the last day for the data reported at the
end of this bulletin) to Thursday of this week the solar flux went
from 101.5 to 103.3 and the sunspot number rose from 48 to 62.

NOAA and the USAF predict rising solar flux for the near term, with
solar flux at 105 on June 17-20, to 110 on June 21-23, 105 on June
24-26 then dipping below 100 after June 28.

Predicted solar flux for ARRL Field Day weekend is 105 on June

Predicted planetary A index for June 17-25 is 10, 8, 5, 8, 8, 5, 18,
15 and 10, followed by 5 on each day through the end of June.  It
seems that a recurring coronal hole may disturb our Earth's
geomagnetic field, with the maximum effect on June 23, two days
before Field Day, but geomagnetic conditions should be very quiet by
Sunday, June 26.

Geophysical Institute Prague predicts quiet conditions for June
17-18, quiet to unsettled June 19, active conditions June 20, and
unsettled conditions June 22-23.  For some reason they don't offer a
prediction for June 21.

Big news this week was the report issued from a meeting of the Solar
Physics Division of American Astronomical Society at New Mexico
State University in Las Cruces predicting another Maunder Minimum -
many decades with hardly any sunspots.  There seems to be a
convergence of several lines of thought which all predict this, but
fortunately there are dissenting experts.

Here is the text of the release:

This contains text and images:

The web site for the conference:

Douglas Biesecker of NOAA's Space Weather Prediction Center
questions this hypothesis of disappearing sunspots.  You can read
his notes here:

Or if that doesn't work for you, try this:

A slideshow accompanies the notes:

Here are several articles on related subjects, the first two
contributed by Scott Bidstrup, TI3/W7RI:

Peter Laws, N5UWY of Norman, Oklahoma wrote: "On the morning of
Memorial Day, May 30, I was alerted to a potential opening on the 2
meter band. I went to the radio room and tuned around. Sure enough -
a W8! I worked W8BYA in EN70 about 1230 km from me in EM15.  My
question is this: Was that a Tropospheric Ducting event or was it
sporadic-E?  It seems to me to be long for Tropo but I don't really
know the upper end for Tropo over land.  Is there some rule of thumb
that operators can use to try to determine which mode made the
contact possible?

"As exciting to me as 2 meter DX contacts are, W8BYA was the only
station I heard on the band!!"

My suspicion is that the mode was sporadic-E, but I don't know.
Maybe some experienced VHF ops can lend an opinion on this.

The July 2011 issue of QST has an informative article by Joel
Hallas, W1ZR on pages 37-38 titled, "Solar Indices - What do they
Mean?"  In the article Joel explains solar flux, sunspot numbers, A
index and K index, and what they mean for the radio amateur.  The
article also gives a nice plug for this bulletin.

Lawrence, GJ3RAX from the Isle of Jersey writes: "Last Friday I had
a phone call from GJ3YHU. That is not unusual as he lives about a
mile from me. This time he was down in Meze in the south of France
where he spends time regularly. He said that he had been hearing
signals on 10 meters and wanted to see if there was a path between
us. I was doubtful that it would be possible as my typical
sporadic-E QSOs are usually to the south of Spain, Gibraltar and
North Africa. The south of France would probably be too close. We
chose a frequency and tried, resulting in a QSO at 5/9 each way.
That lasted for nearly 5 minutes before fading out.

"His equipment was an IC-7000 to a mobile whip. I was using an
IC-756-Pro2 to a Cushcraft R5 which is mounted 10 feet above the
ground here. Using Google Earth I estimated the distance as 485

"By the time I get to replace my broken beam for 6 m the sporadic-E
season will be over but I should be back on that band and the higher
VHF bands later in the year."

Thanks, Lawrence!

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 web page at For an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at Find more good
information and tutorials on propagation at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for June 9 through 15 were 46, 35, 37, 16, 16, 48,
and 48, with a mean of 35.1. 10.7 cm flux was 87.5, 86.7, 84.5,
84.6, 86.6, 99.3, and 101.5, with a mean of 90.1. Estimated
planetary A indices were 11, 8, 11, 9, 8, 7, and 7, with a mean of
8.7. Estimated mid-latitude A indices were 7, 7, 10, 5, 6, 7, and 9,
with a mean of 7.3.


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