Register Account

Login Help

ARRL Propagation Bulletin ARLP035 (2006)

ARLP035 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 35  ARLP035
From Tad Cook, K7RA
Seattle, WA  August 25, 2006
To all radio amateurs 

ARLP035 Propagation de K7RA

Average daily sunspot number was 12 points lower this week than
last, but the geomagnetic indices were higher.  Active geomagnetic
conditions on August 19-22 were the result of an August 19 change in
the IMF (Interplanetary Magnetic Field) opening toward the south,
which allowed a solar wind to affect the earth.  This article from
2003 explains cracks in the magnetosphere, and how they make the
earth vulnerable to geomagnetic effects.

Geophysical Institute Prague predicts quiet to unsettled conditions
for August 25, unsettled August 26-28, quiet to unsettled on August
29, and quiet conditions on August 30-31.  Quiet and unsettled refer
to geomagnetic activity.  Low geomagnetic activity is considered
good for HF communications.

NOAA predicts geomagnetic planetary A index for August 25 through
September 3 at 5, 8, 12, 12, 10, 8, 5, 5, 10, and 20.

Regarding progress of the current sunspot cycle and the decline
toward solar minimum, this ftp site (which you can view with a web
browser) shows the predicted minimum slightly later than recent
projections.  The projection we've been watching, which is updated
infrequently, is in the back of some issues of the Space Environment
Center's Preliminary Report and Forecast, which comes out weekly.
The most recent issue with monthly sunspot number predictions was
the August 1 issue:

It shows a smoothed sunspot number for August through December 2006
of 11, 20, 9, 8, and 7, then dropping to a minimum of 5 for January
2007, then 6 for February through April, and 7, 8, 10 and 11 for May
through August 2007.  This would bring us back to where we are now,
and rising, in August of next year.

But this following prediction, from an ftp site viewable from your
web browser, shows the monthly sunspot number hitting a minimum when
it dips below 12 from February through May of next year:

The above chart also shows the monthly average sunspot number rising
above the number predicted for August 2006 after November of next

In email this week, John Lynch, WA3G in Sparks, Maryland noticed
that in propagation reports on a DX cluster on there is a
mysterious R number.  R is a designation for the Wolf Index, which
is a type of sunspot number.  You can read about the Wolf Index

I used telnet to access, and around 0730z on August 25 it
gave this report: SFI=78, A=8, K=0, R=22.  This matched the Space
Environment sunspot number of 22 for August 24, the most recent
sunspot number available.

You can telnet into (with Windows) by clicking on Start,
Run, then type cmd in the Run window, then click OK.

When you come to a command prompt, type ''telnet'' (without the
quotes), then Enter.  At the next prompt type ''open'',
and you are there.

Chuck Zabriskie, KE5HPY of Houston, Texas was trying to remember a
web site for checking real-time VHF propagation shown on a map,
based upon DX spots that are typed in by users.  That was in our
propagation bulletin 23 for June 9, 2006, and the link is

Dan Kovatch, W8CAR of Castalia, Ohio sent an interesting link about
a ''black aurora'' that he first heard about when watching the
Science channel recently on cable television. The article:

I noticed that there is a Hawaii QSO Party this weekend, detailed at

Here are some possible times for working Hawaii this month from
various places around North America.  These projections were done
with ACE-HF V2.05 propagation software (see ), and
these times are for the very best opportunities for propagation.

From Southern California, 15 meters is possible to KH6, but not
likely.  The best times to try would be 0240-0340z.  20 meters looks
good all day, from 1630-0700z, best signals 1620-1800z and
2315-0600z.  Worst time might be 1840-2010z.  40 meters is promising
from 0230-1350z, and 80 meters from 0500-0650z.

From Alaska (around Anchorage to Fairbanks region) 20 meters is best
0150-0700z.  40 meters is promising from 0340-1500z.

From Seattle, 20 meters looks good 1650-1740z, and 2330-0600z.
0230-1400z looks best for 40 meters.

From the center of continental United States, 20 meters looks good
just after 1600z and 0030-0520z.  40 meters is good 0500-0800z.

From Texas, 20 meters is good 0115-0500z, and 40 meters around 0500
and again around 0800z.

From the middle south, around Tennessee and Arkansas, 20 meters is
the best bet from 0200-0300z and there is a fair chance for 40
meters, 0230-1230z.

From the Northeast USA, centered around New York State, 20 meters
has a fair, but not great chance around 0015-0300z and 40 meters

From the Southeast USA, centered near Georgia, 20 meters looks fair
from 0000-0315z, 40 meters 0300-0900z.

From Southern Florida, 15 meters may have an opening around
0020-0100z, 20 meters looks fair 2345-0330, and very good
0120-0230z.  40 meters looks fair, 0230-0900z and 1000-1040z.

From Ohio, 20 meters looks fair from 0010-0315z, 40 meters

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 .

Sunspot numbers for August 17 through 23 were 26, 29, 21, 15, 24, 14
and 22 with a mean of 21.6. 10.7 cm flux was 85.8, 88.5, 88.8, 88.1,
87.8, 80.8, and 78.3, with a mean of 85.4. Estimated planetary A
indices were 5, 12, 38, 24, 13, 17 and 7 with a mean of 16.6.
Estimated mid-latitude A indices were 4, 9, 21, 14, 10, 17 and 4,
with a mean of 11.3.  


Instragram     Facebook     Twitter     YouTube     LinkedIn