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ARRL Propagation Bulletin ARLP023 (2008)

ARLP023 Propagation de K7RA

QST de W1AW =20
Propagation Forecast Bulletin 23  ARLP023
From Tad Cook, K7RA
Seattle, WA  May 30, 2008
To all radio amateurs=20

ARLP023 Propagation de K7RA

This week we saw only one sunspot, numbered 997, and only on
Memorial Day, May 26.  Alas, this was another sunspot left over from
fading Cycle 23, and the appearance was very brief.  One day it
weakly emerged, and it quickly faded from view.  The previous five
days were spotless; spots appeared on the five days prior to that,
and previous to those spotted days were ten days of no spots.

If our Sun shows no more sunspots today and tomorrow, May 30-31, we
will see a 3-month average of daily sunspot numbers centered on
April just above the values for every 3-month average since the
minimum, centered on October 2007.  The values through April are 3,
6.9, 8.1, 8.5, 8.4, 8.4, and 8.9.  Because this is a three month
average, we won't know the value centered on May until the end of

If these numbers suggest Cycle 24 is stalled, we can compare with
the previous minimum.

Using the same scheme, the 3-month averages of daily sunspot numbers
centered on September 1996 through March 1997 (which includes all
the sunspot data from August through the following April) were 8.7,
10.2, 14.2, 16.4, 11.7, 11.3, and 16.4.

Those are slightly higher values 11 years ago compared with the
current numbers, but notice the six months following the minimum
also seemed to flatten out.  And while the last bottom had slightly
higher average sunspot numbers, it had one longer period of no

If we rank periods of spotless days back to the mid-nineteenth
century, the period between Cycles 22 and 23 had the tenth-ranked
spotless days period, the 42 days from September 13 through October
24, 1996.  Now between Cycles 23 and 24 we have observed two
stretches of spotless days of at least three weeks, a fifty-third
ranked 22 days in September, and the twenty-ninth ranked 28 days in
October and November of last year.

The three longest spotless periods since the mid-nineteenth century
were 92 days leading up to Cycle 15 in 1913, 69 days prior to Cycle
14 in 1901, and 54 days before Cycle 12 in 1879.  You can peruse the
72 longest periods of zero sunspots  lasting 20 days or more, all
ranked from longest to shortest at the site,

Recently we offered notes from Dr. Kenneth Tapping, showing why he
doesn't think this minimum is unusual, to anyone who sends a blank
email to

The response was huge, over 900 requests, and the offer still

Dr. Tapping is an astrophysicist at the Dominion Radio Astrophysical
Observatory in Penticton, British Columbia (see, which supplies the world with their daily
10.7 cm solar flux readings, also reported here.

The notes were offered after Dr. Tapping was widely misquoted
several months ago (and since then, as the mangled quotes seem to
have taken on a life of their own) on various web sites claiming
that Dr. Tapping foresaw possibly decades of no sunspots, and then
trying to link this to several sorts of worldwide calamity.  Some
pieces even claimed that the sunspot cycle hit bottom a year and a
half ago, and that no sunspots have been observed since, a false
claim easily refuted by existing data, widely available.

Last week this bulletin mentioned a free downloadable copy of Bob
Brown's "Little Pistol's Guide to HF Propagation," but it seems it
isn't free after all.  I knew the book was out of print, and had
seen the PDF version at the web address I gave for so long that I
wrongly assumed downloading this was legal, but apparently not.  It
is actually still being published as the same PDF document on a CD
ROM produced by World Radio Magazine.

For the next week expect more of the quiet geomagnetic conditions
seen recently.  The U.S. Air Force and NOAA Space Weather Prediction
Center predict a planetary A index beginning May 30 at 10, 8, 10,
10, and then 5 from June 3-14.  They also predict the next period
when daily solar flux is above 70 to be June 12-20.

Geophysical Institute Prague foresees unsettled conditions May
30-31, unsettled to active June 1, unsettled June 2, quiet to
unsettled June 3, and quiet conditions June 4-5.

Currently we are just a few weeks away from the Summer Solstice, the
longest day of the year.  This officially occurs at midnight GMT on
June 21.  Our current sporadic-E season continues, with often
unexpected openings on 6 and 10 meters.

Ray Soifer, W2RS at his Texas vacation home observed 6 meter
openings observed from EM00 to Colorado, Illinois, Tennessee and
Mississippi.  During last weekend's WPX contest using 100 watts and
a very simple antenna, he worked all continents on 20 meters in just
25 minutes on Saturday at 2220-2245z.

Joaquin Montoya, EA2CCG from Spain reports great openings from his
mobile on 6 and 10 meters on Saturday, including 10 meter FM into
Europe.  On mid-day Saturday he worked 27 stations in Europe on 6
meters with great signals, and he heard a very strong signal from an
EA8 in Africa.  The next day 10 meters was open again, although not
as strong, but 6 meters was not.

Julio Medina, NP3CW in San Juan, Puerto Rico reported great
conditions on 6 meters on May 22-23, working many stations across
the U.S. and into South America, Mexico and the Caribbean.

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 22 through 28 were 0, 0, 0, 0, 12, 0, and 0
with a mean of 1.7.  10.7 cm flux was 69.3, 67.8, 68.5, 68.3, 68,
67.9, and 67.8 with a mean of 68.2.  Estimated planetary A indices
were 9, 10, 7, 6, 4, 3 and 12 with a mean of 7.3.  Estimated
mid-latitude A indices were 7, 7, 4, 7, 3, 2 and 10, with a mean of


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