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ARRL Propagation Bulletin ARLP021 (2009)

ARLP021 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 21  ARLP021
From Tad Cook, K7RA
Seattle, WA  May 22, 2009
To all radio amateurs 

ARLP021 Propagation de K7RA

Do sunspots matter?  Many of us are surprised at how good conditions
can be with zero sunspots.  The weak solar wind and lack of flares
and geomagnetic events likely have something to do with it.  Many
times during more active solar periods the sunspots were welcomed,
but then some event associated with the higher solar activity would
make conditions difficult, disrupt the ionosphere and increase

For example, look back to the Fall of 2003 bulletins via the index
at and in addition to
the text, note the sunspot numbers and A index listings at the end
of each bulletin.  There were plenty of sunspots, but if you look at
Propagation Forecast Bulletin ARLP038 in September, or ARLP044
through ARLP049 around November, there were huge events that drove
the planetary A index to 189 during one week and 162 the next.  This
is hard to imagine today.  Also note the comment in ARLP051 in
December 2003 about the relief from geomagnetic disturbances and
somewhat higher sunspot activity.  Actually, the planetary A index
went as high as 43 one day that week, hardly a quiet geomagnetic
number, but the previous two weeks were quite a bit calmer than the
week prior.

Finding those old bulletins was aided by a graph of planetary A
index progression from January 2000 to present on page 10 in the
Preliminary Report and Forecast of May 12 at,

I apologize that last week's bulletin reached many people several
days late.  The bulletin was dated Friday, May 15, but for some
reason did not get distributed via email until the following Monday
night, and the date of the bulletin was changed to May 20.  The
bulletin mentioned that sunspots were just reappearing the day
before, but by the time it went out, there were already five days of
sunspots.  It turns out it had something to do with a string of
minor unfortunate events, and HQ staff trying to administer bulletin
distribution remotely from ARRL National Convention and the
Hamvention held concurrently in Dayton, Ohio.  Your author was safe
and snug in Seattle (having visited Newington only once, decades
ago), and wants to assure everyone that W1AW staff are really a
brilliant and clever bunch, but Murphy struck.

The report linked from the main ARRL web page appeared as normal
last Friday.

As often is the case, many interesting emails arrived in the past
few days.

Bill Kollenbaum, W4XS/KH7XS of Laupahoehoe on the Island of Hawaii
(the Big Island) has built an impressive station since moving there
from Florida.  Take a look at the station description and click on
the antenna photo at the KH7XS page at  Bill wrote about working European
stations on 15 meters on May 18:

"Since moving to KH6 a couple of years ago, any openings to EU on 15
have been far and few between and I could count on my hands the
total number of days I worked any EU on that band. The total number
of EU in the log on that band has been around a hundred and almost
all have been 569 and considerably weaker.  On 15 this morning (EU
sunset) I put 150 EU in the log from 1930Z until 2100Z, many of the
stations were a true 589 and 599.  The opening ran from the Ukraine
and Scandinavia down to LZ and over to EA and G.  There seemed to be
little geographic advantage to the stations with OH0R calling in
with a 589 report, and UK , Italian and Germans  all hitting the S9
mark here.  Conditions were outstanding. What a difference a small
number of sunspots make, coupled with quiet conditions and a big
daylight path!"

Bill's path to Europe is a long one.  To Spain, the beam heading is
not much different from the heading here in Seattle, a polar path at
23 degrees.  But the path to Spain at around 8,000 miles is much
longer than the 5,300 miles from Seattle or the 4,000 mile path from
Ohio, or 3,400 mile path from Boston.

There were several comments about the comments I made about EMP and
vacuum tubes in last week's bulletin.  Gene Dathe, NA0G of Spring
Valley, Minnesota pointed out that vacuum tubes are far more
resistant to an EMP blast compared to solid state devices providing
they are turned off.  While operating, they could suffer from the
same sort of risks.

Bob Voss, N4CD decided to research stories about the great
geomagnetic storm of 1859.  He sent along the link and wondered if the
stories of fires could have been inspired by reports of a "blood red
horizon."  He sent this link from Spaceweather
Canada, and notes there were no fires reported for the 1859 event.
Bob notes that the NASA account at
actually mentions fires in connection with the 1859 flare.  There is
also an old nineteenth-century NY Times article at

Over the near term it looks like more quiet conditions.  We had a
nice seven day run of sunspots, but do not know when they will
return.  Geophysical Institute Prague says quiet conditions should
prevail May 22-28.  NOAA and the US Air Force predict solar flux
settling back to 70, then rising again June 5-17.

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 May 14 through 20 were 18, 12, 15, 13, 14, 11,
and 0 with a mean of 11.9.  10.7 cm flux was 73.9, 73.7, 74.2, 74,
72.9, 72.3, and 71.5 with a mean of 73.2.  Estimated planetary A
indices were 8, 2, 5, 3, 4, 5 and 4 with a mean of 4.4.  Estimated
mid-latitude A indices were 8, 2, 3, 2, 2, 2 and 4 with a mean of


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