ARRL Propagation Bulletin ARLP049 (2009)

ARLP049 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 49  ARLP049
From Tad Cook, K7RA
Seattle, WA  November 30, 2009
To all radio amateurs 

ARLP049 Propagation de K7RA

This is a follow-up to last Wednesday's pre-Thanksgiving Propagation
Forecast Bulletin ARLP048.  It was a little early to provide the
complete Thursday through Wednesday sunspot, solar flux, and A index
that normally appears in Friday's bulletin, so we are including it
here at the bottom of this bulletin.  The next bulletin will be out
four days from now.

Our exciting period of nearly daily sunspot activity ended with the
first spotless day on November 23, and the Sun has been blank since
then.  A look at the STEREO image at
shows a bright active area perhaps five days over the eastern
horizon, but we don't know if that will give us sunspots or not.

As the two STEREO craft move further from earth, the visual gap on
the Sun's far side is gradually closing, and we look forward to the
time in 2011 when all of the Sun will be visible from STEREO and
earth.  Currently the gap is about 14.3%.

You can calculate the approximate percentage of the Sun in that dark
spot by using the "Where is STEREO?" link on the STEREO home page,
which takes you to
Check the "Separation angle A with B" stat at the bottom, subtract
that number from 180, divide the result by 360, then multiple that
result by 100 to get a percentage figure.

You can check future dates by clicking on the "STEREO Orbit Tool"
link, taking you to

When you check February 1, 2010 at 0000 UTC it yields a separation
angle of 135.197 degrees.  Subtracted from 180 degrees, this yields
44.803, divide that by 360, then multiply by 100, and you get
approximately 12.45% remaining on the dark side.  October 1, 2010
yields 5.58%, and January 1, 2011 just 1.26% in the dark.  Check the

WorldRadio Online posts a new issue on the twentieth of each month,
and each has a column on propagation by Carl Luetzelschwab, K9LA.
You can download it at, and read Carl's
article on "The Impact of Deep Solar Minimum on 160m Propagation."
Carl's column begins on page 28 of the current December issue.  The
January 2010 issue should appear online on December 20.

Past bulletins mentioned the incredible WSPR mode for weak signal
communication.  Doug Hawkins, W3HH of Ocala, Florida was using WSPR
mode on November 18 on 30 meters, and copied AA1A in Marshfield,
Massachusetts -- 1,105 miles away.  Not unusual, except that AA1A
was running only 10 microwatts!  Doug points out that this signal is
20 dB below 1 mW.  Doug says that several other stations have copied
AA1A, but so far this is the longest distance record.

Doug thought the distance was about 900 miles, but I looked up the
address for each station at the top of the ARRL web page at, then plugged the addresses into a computer
atlas to find the exact latitude and longitude coordinates, then
used W6ELprop to calculate the distance, which turned out to be over
20 percent further than Doug's estimate.

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 November 19 through 25 were 30, 31, 14, 13, 0,
0, and 0 with a mean of 12.6.  10.7 cm flux was 76.7, 76.2, 75.8,
76.3, 75.7, 74.7, and 74.2 with a mean of 75.7.  Estimated planetary
A indices were 2, 1, 8, 4, 0, 6 and 5 with a mean of 3.7.  Estimated
mid-latitude A indices were 0, 2, 6, 2, 0, 3 and 4 with a mean of