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ARRL Propagation Bulletin ARLP034 (2011)

ARLP034 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 34  ARLP034
From Tad Cook, K7RA
Seattle, WA  August 26, 2011
To all radio amateurs 

ARLP034 Propagation de K7RA

Solar activity rose this week, with the average daily sunspot number
increasing over 40 points to 66, and average daily solar flux up
over 13 points to 101.9.

Predicted solar flux for August 26 is 110, and 115 for August 27-28,
110 for August 29 to September 1, 105 for September 2-3, 100 for
September 4-5, 95 on September 6-7, and bottoming out at 90 on
September 8-12.  The next peak of activity is predicted for
September 22-23.

Predicted planetary A index is 5 for August 26-27, 10 on August 28,
8 on August 29, and 5 on August 30 through September 2, then 8 on
September 3, 10 on September 4-6, 7 on September 7, and 5 on
September 8-10.

Geophysical Institute Prague predicts quiet conditions for August
26, unsettled on August 27-28, quiet to unsettled August 29 and
quiet conditions on August 30 through September 1.

A story forwarded from a British newspaper by a reader warned that
"a huge mass of electrically charged particles thrown out by a giant
eruption on the Sun is due to strike the earth tonight." But the
article itself is undated, and the web page continuously updates to
show the current date. The link to the article was sent to me on
August 21, but the event didn't happen then, and is not happening
now, nor is such an event predicted for the next few days. Down the
left margin of the page are ads for astrologers, and on the right
margin are links to over 80 stories about celebrity gossip.

If you do a web search for phrases from the article - which is at
- you find it quoted all over the net by people assuming that this
is about to happen, some of them quite alarmed. But looking at the
latest prediction from NOAA/USAF at shows no
predicted rise in the A index, which would be large if such an event
were predicted.

So what date was the article published? I doubt if this newspaper
has had a science editor for a number of years, so perhaps they keep
running the same article with its dire warnings, and only the
celebrity gossip changes.

The key to the date of this article lies in searching the newspaper
archive for the headline.  If you enter a portion of the headline
into the search box next to the article, the actual date is
revealed: October 29, 2003.  This is nearly eight years ago.  Now we
know why nobody predicted this event. In these fast moving times,
2003 might seem to some like ancient history.

Try doing a web search of a phrase from this article. Some of the
results are quite funny.  You will see it referenced all over the
web as if it just happened and were breaking news.

Last week's bulletin mentioned the new issue of WorldRadio expected
last Saturday, which would have an updated propagation column by
K9LA.  The new September issue didn't actually appear online until
several days later.  You can read it now at

The propagation column by K9LA, Carl Luetzelschwab pays tribute to
the late Bob Brown, NM7M and his writings about propagation for the
amateur community.  Carl mentions that one of Bob's popular books is
available for download from Carl's web site.  Just go to and click on General on the
left side of the page, then right-click the link for "Little
Pistol's Guide to HF Propagation" to download the PDF.

We are just a few weeks away from the Autumnal Equinox, a time when
we see better HF propagation than we did during the summer. You can
check the effect of seasonal change by running two instances of a
propagation program, and switching back and forth to see the same
projection over two different dates.

You can download W6ELprop from and try
what I did, which was to compare August 2 with September 22.  The
predicted smoothed sunspot number for August was 59, and for
September it is 62.  You could use those numbers, or use the same
sunspot number on both projections to isolate the seasonal effect.

I ran my projection between Atlanta, Georgia and England.  You bring
up Atlanta coordinates in W6ELprop by entering the prefix W4, and
England with the G prefix.  You can see the generally improved
signal strengths and longer openings in the September prediction.

If you want the latest smoothed sunspot numbers for this month and
off into the future, go to and look at the
table on page 18.  Every 4-5 issues they have an updated projection
for the current solar cycle.

Finally, do you think Cycle 24 is weaker and still progressing
slower than previous solar cycles?  You are correct.  For a
comparison of Cycles 21, 22, 23 and 24, check

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 August 18 through 24 were 53, 46, 59, 66, 82,
81, and 75, with a mean of 66. 10.7 cm flux was 97.8, 98.2, 100.5,
100.9, 108.2, 103.7, and 104.1, with a mean of 101.9. Estimated
planetary A indices were 3, 2, 5, 3, 7, 9, and 6, with a mean of 5.
Estimated mid-latitude A indices were 1, 1, 4, 3, 5, 8, and 5, with
a mean of 3.9.


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