ARRL Propagation Bulletin ARLP039 (2007)

ARLP039 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 39  ARLP039
From Tad Cook, K7RA
Seattle, WA  September 21, 2007
To all radio amateurs 

ARLP039 Propagation de K7RA

We're on the road this week in our nation's capitol.

Fifteen days in a row with no sunspots, but this may change soon.
Take a look at sunspot numbers compared to solar flux for the
current third quarter of 2007 at,  Notice that
when there are zero sunspots, the solar flux is always below 70.
Recently the flux value has been below 70, and for some time now the
US Air Force has predicted a slight rise in solar flux to 70 for
today, September 21.  You can see those predictions at,

If we examine predictions from early September on that page, note
they show a return to a solar flux of 70 for September 17, then
later forecasts show it creeping out to September 18, then 19, and
finally for yesterday the prediction for today is 70.

We also see the return of sunspot group 970 set for September 21-23,
from the September 21 Solar Region Summary at, .  It would be
great to have at least one sunspot when Fall returns.  The official
Autumnal Equinox is this weekend, September 23 at 0951z.

Along with no sunspots, geomagnetic indicators were very stable.

The US Air Force predicts a solar flux value of 70 for September 21
through October 1, and a planetary A index of 10, 15, 15, 10, 8 and
5 for September 21-26.

Geophysical Institute Prague predicts unsettled conditions for
September 21, unsettled to active September 22, unsettled for
September 23-24, and quiet on September 25-27.

Even with no sunspots, you can still get good results with a modest
station.  Rod Vlatch, NN0TT of Willmar, Minnesota reports that with
100 watts and a modest commercial vertical antenna he worked the
3B7C expedition (Saint Brandon Island in the Indian Ocean) on 40
meter CW on September 14.  This is CW DXCC #291 for him, all with
the same modest setup.  Chip Margelli, K7JA, worked them on 40
meters at 0214z long path on September 12 using a 2/3 size loaded
dipole at 30 feet from Southern California.

Last week's Propagation Forecast Bulletin ARLP038 mentioned and this week Floyd Chowning, K5LA of El Paso,
Texas sent in a link to an interesting report on 10-meter sporadic-E
activity based on data from PropNET.  Read about it at,

Bob Marston, K6TR of Fremont, California says, "If Cycle 23
continues through January 2008 it will match Cycle 20 as one of the
longest in recent history.  You have to go back to Cycle 9 in the
Mid 1800s to find a longer one.  My own estimate is Cycle 23 will
end in Feb 2008 with a SSN between 6.8 and 7.2."

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 September 13 through 19 were 0, 0, 0, 0, 0, 0
and 0 with a mean of 0. 10.7 cm flux was 66.4, 66.8, 67.7, 67, 66.9,
66.5, and 66.8 with a mean of 66.9. Estimated planetary A indices
were 2, 4, 4, 2, 2, 3 and 4 with a mean of 3. Estimated mid-latitude
A indices were 1, 3, 3, 2, 1, 2 and 2, with a mean of 2.