ARRL Propagation Bulletin ARLP022 (2008)

ARLP022 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 22  ARLP022
From Tad Cook, K7RA
Seattle, WA  May 23, 2008
To all radio amateurs 

ARLP022 Propagation de K7RA

This week several new sunspots appeared for five days, but they were
all leftover spots from cycle 23, not new cycle 24 spots. But this
is okay, because at the sunspot minimum we appreciate any spots we
can get.  May 16-20 saw daily sunspot numbers of 34, 23, 30, 28, and

Keep in mind that a sunspot number of 34 does not mean there were 34
sunspots last Friday.  Instead, the numbers represent a somewhat
arcane calculation that accounts for the number of sunspot groups
and the size of each group.  The count gets 10 points for each
sunspot group, and one point for each spot within the groups, the
designation of these different areas within the groups seeming
somewhat arbitrary to a layman such as myself.

So 34 could mean that there are three darkened areas, with one of
them counting as two spots, the other two just one each.  Presumably
the same number would describe the sun with two darkened areas
facing Earth, and each counting for seven spots.  Thirty plus four
is the same as twenty plus fourteen, but this week there were three

For at least a couple of weeks the U.S. Air Force and the NOAA Space
Weather Prediction Center forecast a planetary A index of 25 for May
21, but on May 20 the prediction was downgraded to 15.  The actual
planetary A index for that day was 13, while the mid-latitude A
index was 9 and Alaska's College A index, taken near Fairbanks, was
19.  The earlier number was based on an expectation of returning
coronal holes and solar wind streams, which proved to be weaker than

Currently they expect quiet geomagnetic conditions and another
prediction for a planetary A index of 25 just before the start of
summer, on June 17.  Geophysical Institute Prague calls for
unsettled conditions May 23-24, quiet to unsettled May 25, quiet May
26, quiet to unsettled again on May 27-28, and unsettled for May 29.

This weekend is the CQ World Wide WPX CW Contest, and of course, we
don't expect any sunspots, but we don't expect disruptions either.
Using a technique known as helioseismic holography, the Solar and
Heliospheric Observatory's Michelson-Doppler imager detected a high
latitude sunspot on our sun's far side on May 17.  If it doesn't
fade away first, perhaps we may see that still hidden spot slip into
view next week.

Right now we are in the main sporadic-E skip season, and we have
reports.  Mike Shaffer, KA9JAW of Tampa, Florida regularly sends
reports of television DX, and sends video and audio recordings as
well.  On channel two he has been receiving Dominican Republic, at
2230-2315z, and a Canadian channel from Toronto, about 1,100 miles
from his home.

N0JK, Jon Jones of Wichita, Kansas documented nine 6-meter contacts
between KH7Y, south of Hilo on the western side of the island of
Hawaii on May 19.  He noted that the best propagation seemed to be
to Iowa and Illinois.

David Fisher, KA2CYN of New City, New York (up the Hudson River from
Manhattan, and on the west side) said there was a nice opening on 10
meters to the West Coast on May 16, and around 2110z he talked to
K6CJA in California.

This week an email arrived from Richie Ranta, K8JX of Grand Rapids,
Michigan asking about some material about sunspots and propagation
for his club's newsletter, ''The Open Feed-Line'', from the Michigan
Amateur Radio Alliance (see

I didn't have any articles prepared for him explaining some of the
basics, but suggested some resources.  I didn't know if he was
reading the sometimes shortened bulletin on the ARRL home page, or
the complete text at  The complete
text has links toward the end of each bulletin for suggested reading
on propagation.  This is the same version you get if subscribed via

Another good source is any edition of the ARRL Handbook, or even any
of the old Radio Amateur's Handbook editions going back many years.
Each has a chapter devoted to propagation, which is a good basic

Also, this Flash slide-show is quite good at explaining the

Another good source is NM7M, Bob Brown's book, ''The Little Pistol's
Guide to HF Propagation''.  Unfortunately, it has long been out of
print, but some local libraries may have it.  Seattle Public
Library, where I live, has several copies, in fact I have one
checked out right now.  Fortunately, it is available as a pdf which
you can download from K6PKL's web site at

I shouldn't forget the excellent material from Carl Luetzelschwab,
K9LA on his web site at  Carl is
quite an expert on propagation, and has been an invaluable resource
for this bulletin.

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 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 15 through 21 were 0, 34, 23, 30, 28, 23,
and 0 with a mean of 19.7.  10.7 cm flux was 71.1, 71.6, 71.2, 71.6,
68.9, 68.6, and 69.1 with a mean of 70.3.  Estimated planetary A
indices were 4, 4, 2, 3, 8, 10 and 13 with a mean of 6.3.  Estimated
mid-latitude A indices were 2, 3, 1, 2, 5, 7 and 9, with a mean of