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ARRL Propagation Bulletin ARLP011 (2009)

ARLP011 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 11  ARLP011
From Tad Cook, K7RA
Seattle, WA  March 13, 2009
To all radio amateurs 

ARLP011 Propagation de K7RA

Last week's Propagation Forecast Bulletin again mentioned briefly
appearing sunspots, and it happened again this week.

For just two days, another Cycle 23 spot appeared, numbered 1014.
The latitude of the spot was consistent with an old and fading solar
cycle.  As this period of quiet Sun drags on, statistic based
projections of a return to solar activity continue to be pushed out.

Early Friday morning the planetary K index is rising to 5, then 5.
This is from a stream of solar wind bearing down upon us.  NOAA and
the US Air Force predict a planetary A index of 15 for today (March
13), 10 for Saturday, then back to 5.  Tough to forecast this far
out, but they show that active region returning on April 9.

On March 10 at 2333z the Australian Space Forecast Center released a
bulletin predicting "increased geomagnetic activity expected due to
coronal hole high speed wind stream from 13-14 March 2009."

The Center has 26 email alert services that anyone can subscribe to.
Check and click on
any subject title to subscribe to that list.

Geophysical Institute Prague projects unsettled conditions for March
13-14, and quiet conditions March 15-19.

Chuck Zabreskie, KE5HPY of Houston, Texas wrote with an anecdote
about last weekend's propagation.

Chuck wrote, "Thought I'd mention a pleasant surprise last Saturday
afternoon (2100-2200Z) during the recent International DX contest.
My rig is 100W into a 35' OCF (off-center fed) dipole, nothing
fancy.  I need to look where the others aren't piled up.  20m was
busy as you'd expect so I took a look at 15m after looking at W6EL
Prop.  Great signals from Peru, Argentina and Brazil among others,
but little heard to the north of my QTH in Houston, Texas (30 deg
N).  Feeling lucky, I looked at 10m and also had great copy from
Argentina and Brazil until 2230.  Nothing in W6EL suggested that
should be where it appeared.  Again, nothing heard to the north of
them or here and relatively few US operators coming back to their
CQs.  Seemed like a pipeline between TX/AZ into that zone."

Chuck continues, "Nothing like a contest to demonstrate what the
bands permit.  I'll be calling CQ on 10m this Saturday."

He ends with, "Is this a seasonal effect due to the equinox?  Is it
common to see a small zone on either end of the pipe?"

I thought I would check into Chuck's results using W6ELprop, which
should factor in the equinox.  Although the program is meant to be
used with the predicted smoothed sunspot number for the month, I
used a sunspot number of 12 -- the actual daily sunspot number for
March 6-7.

Chuck is near Rice University in Houston, and actually sits to the
south of the 30th parallel, at 29.725 degrees North latitude.

Using March 7 with a path to Brazil at 15 degrees south, 54 degrees
west, I show that as a good time for propagation on 15, and even 10,
and especially 20 meters, using the exact coordinates for Chuck's
QTH.  But I wonder why other North American stations weren't working
the South America stations?  But it is interesting that W6ELprop
shows much less favorable conditions for other stateside areas into
Brazil, even from Dallas, which is around the 33rd parallel.  Chuck
and I will have to compare our results using W6ELprop.

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 a detailed
explanation of the numbers used in this bulletin, see  An archive of past
propagation bulletins is at

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

Instructions for starting or ending email distribution of this
bulletin are at mail.

Sunspot numbers for March 5 through 11 were 0, 12, 12, 0, 0, 0, and
0 with a mean of 3.4.  10.7 cm flux was 69.2, 69.1, 69.1, 68.9,
69.1, 68.8, and 68.9 with a mean of 69.  Estimated planetary A
indices were 3, 2, 1, 8, 2, 3 and 3 with a mean of 3.1.  Estimated
mid-latitude A indices were 3, 0, 0, 7, 1, 3 and 2 with a mean of


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