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ARRL Propagation Bulletin ARLP039 (2008)

ARLP039 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
From Tad Cook, K7RA
Seattle, WA  September 19, 2008
To all radio amateurs 

ARLP039 Propagation de K7RA

Last week saw another brief sunspot appearance followed by a quick
fade.  This was an old Cycle 23 spot, numbered 1001, and it resulted
in a sunspot number of 12 for September 11.

Solar flux values (a measure of 2.8 GHz radiation detected by a
parabolic antenna aimed at the Sun in Penticton, British Columbia)
were a bit higher this week, although in normal times any flux value
under 70 is considered quite low.  The September 16 solar flux was
69.4, the highest it has been since May 18, 2008.

Sunspot 1001 was similar to other recent spots, which made only a
weak, brief appearance.  Yesterday, Belgium's Royal Observatory
produced a report titled, "The Sunspot Number Clarified," which
talks about these weak spots making brief appearances, and the
issues they raise during a sunspot minimum.  It says that some
"human arbitration" is required to determine what is counted as an
observed sunspot, and they base this on data from multiple
locations.  If some locations see no spot on the day in question,
the sunspot can still be counted if it is seen by multiple other

You can read about it via if you click on the
report title dated September 18, then click on the link marked
"Handling very low activity levels."  You can download this along
with all other parts of the report at,

For the near term, nothing indicates any emerging sunspots, and the
geomagnetic indicators should remain quiet with a planetary A index
of 5, until the end of the month.  September 30 through October 2
the planetary A index is expected to be 8, 30, and 8.  Eight is a
low number, but thirty indicates a geomagnetic storm, probably
expected from a recurring coronal hole spewing a strong solar wind.

While the lack of sunspots is discouraging, the lack of geomagnetic
activity is welcome.  In times passed we had good sunspot activity
but constant solar wind, disturbing geomagnetic conditions and
making HF propagation very difficult.  On Tuesday, September 23
scientists from the Ulysses International Solar Mission will
participate in a NASA teleconference which will talk about the solar
wind now being at a 50-year low.  The teleconference begins at 12:30
PM EDT (1630z) and you can hear live audio at,  You can see visuals that will
accompany the presentations at,

This week we saw a post by John Sahr, WB7NWP, a professor of
geophysics and electrical engineering at the University of
Washington.  He noted, "I've been watching solar wind data daily for
nearly a decade, and I have *never* seen such a long period of such

This Monday, September 22, marks the Autumnal Equinox, the first day
of the Fall season.  This is generally considered a good time for HF
communications, and the Sun's energy shines equally on the northern
and southern hemispheres.  When I use a propagation prediction
program to compare next Tuesday with the same date three months ago,
there are some differences.  For September from Seattle to New
Zealand, 15 meters offers a reasonable opportunity, but no
possibility in June.  17 meters has a longer opening in September,
although the June numbers look good later in the evening.  20 meters
is good from 0330-0530z in September, but in June the opening ends
30 minutes earlier, and signals aren't as strong.  In September 30
meters is very strong all night long from 0500-1530z, but in June
the openings are brief, at 0430-0630z and again from 1400-1500z.

Last week's Propagation Forecast Bulletin ARLP038 mentioned PY2ZX in
Jundai, but an email from PU2PTH, Paulo de Tarso in Sao Paulo,
Brazil mentioned that Jundai is in Southeast Brazil, not Northeast.
There are actually several places named Jundai in Brazil, but PY2ZX
is not in the Jundai in Northeast Brazil near Recife, but instead
not far from Paulo in Sao Paulo.

Brian Webb, KD6NRP of Ventura County, California says that despite
the low solar activity, he's been having a great time on HF running
less than 100 watts with a modest antenna system on 160 through 10
meters.  He has only been on HF since February, 2007, and has made a
long list of contacts all over the world.

Similar comments came from Mark Mokoski, K1PU/VK2IFH of Higganum,
Connecticut, who decided to rework DXCC and WAS with his new call
(he was WA1ZEK for 30 years).  He is using 100 watts with an 80
meter dipole and a trap vertical, and over the past two months he
has worked 93 countries, mostly on 30 and 40 meters.  He didn't
mention it in his email, but I noticed at his web site that he has free ham radio software he's
written, including a telnet client for DX cluster operation.

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

Sunspot numbers for September 11 through 17 were 12, 0, 0, 0, 0, 0,
and 0 with a mean of 1.7.  10.7 cm flux was 66.9, 66.3, 66.4, 66.8,
67.5, 69.4, and 67.1 with a mean of 67.2.  Estimated planetary A
indices were 2, 2, 0, 6, 15, 9 and 3 with a mean of 5.3.  Estimated
mid-latitude A indices were 1, 0, 0, 4, 11, 7 and 3 with a mean of


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