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ARRL Propagation Bulletin ARLP018 (2007)

ARLP018 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 18  ARLP018
From Tad Cook, K7RA
Seattle, WA  April 27, 2007
To all radio amateurs 

ARLP018 Propagation de K7RA

In the past few days sunspots have reappeared after six days of
nothing.  In April so far we've seen 18 days with 0 spots.  But
currently a large sunspot, number 953 is rolling into view.  A solar
wind stream is also expected to hit earth, causing geomagnetic upset
on Saturday, April 28.  The Australian Space Forecast Centre
predicts quiet to unsettled conditions on April 27, active to minor
storm on Saturday, April 28, and active conditions on April 29.  The
U.S. Air Force predicts planetary A index from April 27 through May
1 at 5, 25, 15, 10 and 8.  Similar predictions from Geophysical
Institute Prague give us quiet conditions for April 27, active on
April 28, unsettled to active April 29, unsettled April 30, quiet to
unsettled on May 1, and back to quiet on May 2-3.

Lots of news this week on the solar minimum and predicted solar
maximum.  On April 25, a Solar Cycle 24 Prediction Panel, consisting
of members from NOAA, NASA and other agencies looked at all
available predictions and attempted to reach a consensus.  It looks
like the minimum between cycles 23 and 24 may not occur for another
year, until March 2008, a year later than recently reported.  The
accuracy is expected to be plus or minus six months.  The peak of
cycle 24 is expected to occur in October 2011 if there is a large
solar cycle, and August 2012 for a small cycle.  You can see their
statement at,

Many people sent links to articles about this.  Frank Donovan, W3LPL
of Glenwood, Maryland sent a couple of links, including one with a
graphic representation of a range of predictions at,  Also check for other info, including
PowerPoint presentations.  If you don't have PowerPoint, you can
find a free PowerPoint viewer to download for Mac or Windows by
searching for the two words PowerPoint Viewer in Google, or any
other search engine.

An AP story is at,, and on
the web at, link.

We received a large volume of mail this week, and hope to get to
more of it in the next bulletin.  Among reports was some unusual 6
meter backscatter propagation observed by Bill Van Alstyne, W5WVO of
Rio Rancho, New Mexico on April 21.

I'll let Bill describe it: "Greetings from New Mexico, DM65. Just
finished a very unusual opening off of a pre-season Es cloud in
northern Mexico, approximately 2315-0100z. Many central Mexican
stations in XE1/XE2 with 59++ sigs, but the real news was the
amazing strength of the backscatter signals coming in from Arizona,
New Mexico, Utah, Texas, and California, all peaking with the beam
pointed due south. Was able to work a couple of new close-in grids
in AZ, as well as many other grids I already had. Strongest
backscatter signals were from Bob, W7UT, in southwest Utah; Bud,
N7CW, in Prescott, AZ; and Tommy, W7RV, in Scottsdale, AZ. All were
consistently 56/57 until the propagation began to weaken around

Bill continues, "This is by far the strongest backscatter I've ever
heard on 6M. As a rule, Es clouds (due to their very thin, flat
architecture) are very poor backscatter producers; the only previous
backscatter I've ever worked off of 6M Es was extremely weak. This
backscatter propagation was ragchew quality, and lasted virtually
without QSB for over an hour."

Also this week we saw some of the early 3-D images from the NASA
STEREO satellites.  To view in 3-D, you need those paper glasses
with a red filter covering the left eye, and cyan filter over the
right eye.  You can see the images at,
They also have info on where to find the glasses.  I found mine for
well under a dollar at Science, Art and More, a shop that sells
products for science education in my neighborhood.

I must admit I was a little disappointed, but only a little.  At the
distance these solar images are taken, the depth effect of the sun
shows it as very close to a perfect sphere, in my estimation.
Perhaps I was hoping for detailed looks at the surface with
exaggerated three-dimensional effects that would enhance the
perception of depth and detail.  But I have no doubt that the images
shown on that page are probably accurate, more so than what I had

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,

Sunspot numbers for April 19 through 25 were 0, 0, 0, 0, 0, 0 and 14
with a mean of 2. 10.7 cm flux was 68.3, 68.5 68.7, 68.9, 69.1,
73.2, and 76.5, with a mean of 70.5. Estimated planetary A indices
were 6, 3, 2, 10, 18, 4 and 5 with a mean of 6.9. Estimated
mid-latitude A indices were 4, 2, 2, 8, 10, 5 and 4, with a mean of


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