ARRL Propagation Bulletin ARLP038 (2007)

ARLP038 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 38  ARLP038
From Tad Cook, K7RA
Seattle, WA  September 14, 2007
To all radio amateurs 

ARLP038 Propagation de K7RA

The Sun has been blank, with no visible sunspots, for the past seven
days, September 7-13.  We may not see another sunspot until
September 22, just before the Autumnal Equinox.

Thursday evening, September 13,
( mentioned a coronal wind hitting earth
this evening, September 14.  The IMF points south, which makes earth
vulnerable to solar wind, but other sources don't call for an
increase in geomagnetic activity today.

We might assume that a solar wind from 27 to 28 days ago could
return at this time, based on the rotation of the Sun relative to
earth.  But looking back four weeks on, does not reveal
any heightened activity.  Of course, it could be that the
Interplanetary Magnetic field pointed north, protecting earth from
the coronal wind.

U.S. Air Force Space Weather Operations predict continued quiet
geomagnetic conditions, with a planetary A index for September 14 at
8, then 5 every day through September 20.  Geophysical Institute
Prague predicts quiet to unsettled conditions September 14-15 and
quiet conditions September 16-20.

Each month we are checking the Preliminary Report and Forecast of
Solar Geophysical Data from NOAA SEC for updates to the forecast for
this sunspot cycle.  The current edition is at 1671, dated September
12, at  Compare the table
of predicted smoothed sunspot numbers on page 9 with number 1666
dated August 7.  Note the latest forecast has a more pronounced
minimum, all centered around March and April 2007.

Floyd Clowning, K5LA and Eva Tupis, W2EV sent in some information on
PropNET (see, the automated network of low
power BPSK stations dedicated to detecting propagation paths on 160,
30, 10, 6 and 2 meters, and plotting them on maps.  This was
mentioned briefly in Propagation Forecast Bulletin ARLP015 about
five months ago.

The PropNET website has all the information on setting up one of
these stations, and of course, you don't have to be a participant to
use it.  All the data that is generated appears on the web site.

One thing PropNET needs is more overseas participation.  The network
currently gives good propagation indicators in the United States,
but could sure use a few stations outside North America.

Check the October 2007 issue of QST for an interesting article
concerning the bottom of this solar cycle by Steve Ford, WB8IMY.
Titled "Waiting for the Sun," Steve gives us ideas on how to best
utilize the available propagation when there are few sunspots.

Finally, Ken Fletcher of the British DX Club sent in a link to, a neat site devoted to the current and
upcoming sunspot cycles.

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 6 through 12 were 12, 0, 0, 0, 0, 0
and 0 with a mean of 1.7. 10.7 cm flux was 66.7, 67.1, 66.6, 66.7,
66.9, 66.1, and 65.9 with a mean of 66.6. Estimated planetary A
indices were 13, 12, 6, 2, 2, 2 and 2 with a mean of 5.6. Estimated
mid-latitude A indices were 8, 10, 3, 2, 2, 2 and 2, with a mean of