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ARRL Propagation Bulletin ARLP040 (2007)

ARLP040 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 40  ARLP040
From Tad Cook, K7RA
Seattle, WA  September 28, 2007
To all radio amateurs 

ARLP040 Propagation de K7RA

Last week's report stated the possibility that zero-sunspot days
were about to end, but no such luck.  Instead we've seen no sunspots
for three weeks straight, since September 7.

The September 20 forecast from NOAA and the US Air Force showed
solar flux values rising to 70 on September 21.  (See  The next
day's prediction reverted to 67
(  The
September 21 prediction had solar flux rising to 70 again, but not
until September 29 to October 1, then falling back below 70, then
back to 70 again for October 18-28.

Now the September 27 forecast has solar flux staying around 67-68
through November 11.  You can see all the latest daily forecasts for
solar flux and planetary A index at  The possible end
to the stretch of zero sunspot days was based on the observation
that when the solar flux is 70 or higher, there is at least one
visible sunspot.  This makes it seem that we are still at the bottom
of the cycle, or haven't quite reached it.

Those daily forecasts are posted after 2100z.  There is a new
sunspot 970 emerging, so perhaps the September 28 forecast will show
solar flux back to 70 or higher.  There is currently a solar wind
hitting earth, and currently the interplanetary magnetic field
points south, which leaves earth vulnerable.  That same forecast on
September 27 predicts a planetary A index for September 28 to
October 3 at 15, 25, 12, 8, 8 and 15, so we may see unsettled to
active geomagnetic conditions on Saturday, September 29 and again
Wednesday, October 3.  Already early Friday morning UTC (which is
late Thursday on the West Coast) we've seen the planetary K index as
high as 6.  Lately with quiet conditions the K index has been 1 or
2.  Above 3 is considered unsettled or active geomagnetic

Geophysical Institute Prague predicts unsettled conditions for
September 28, unsettled to active September 29, unsettled September
30, quiet October 1, unsettled October 2-3, and quiet to unsettled
October 4.

Jeff Lackey, K8CQ of Saint Simons Island, Georgia wrote in with an
interesting observation.  He created a graph (which unfortunately is
not on the web for viewing) which plots periods in which the solar
flux drops below 80 for extended periods.  It shows the longest run
at the end of cycle 22 was from January 8 through July 7, 1996, 182
days.  The second longest run from 11 years ago was 112 days from
August 2 to November 21, 1996.  The latest and also the longest run
at the end of the current cycle 23 began on June 9, 2007 and so far
runs 112 days through September 28.  The September 28 morning
reading at Penticton (the noon reading is the official value) has a
very low solar flux value of 64.4.

The latest forecast from the Air Force shows solar flux below 80 for
the next 45 days, so if this turns out to be true, that would put
this run up toward the longest one from 11 years ago.  We are today
already equal to the second longest run of cycle 22, and are in the
longest run of the current cycle.  The second longest run for the
current cycle is 77 days, ending after April 25, 2007.

Note there is nothing magic about a solar flux value of 80, but Jeff
is a numbers guy and found this to be an interesting threshold for
his analysis of solar minima.

Despite the lack of sunspots, hams are still communicating around
the world, and reports of working 3B7C with modest stations are
still coming in.  WA2VQW worked them on 30 meters from his car at
2115z on September 18 while sitting at a traffic light in Hawthorne,
New York.  Mike was on his way to higher ground, but never made it,
instead working the DXpedition while stuck in traffic.  W4WNT of Oak
Island, North Carolina reports a 30 meter 3B7C contact at 0212z on
September 22 using an 80-20 meter fan dipole bent around his deck at
30 feet.

On September 18, Ken Tata, K1KT of Warwick, Rhode Island noticed an
online propagation map tracking 2 meter APRS stations showed a path
from Rhode Island to Newfoundland's Avalon Peninsula.  Ken was
running 50 watts into a dipole, a driven element removed from an 11
element Yagi and mounted on a pole.  He reports, ''I worked VE1PZ, in
FN85, 100 mi north of Halifax; VE1HD, FN95, 100 mi east of Halifax;
and VE1AHM, FN76, near Moncton, New Brunswick''.  He reported that
many of the better equipped stations in Southern New England were
working into the Maritime Provinces on 432 and 1296 MHz.  Ken didn't
say what mode he used.  Ken sent along web-based VHF propagation
sites he likes for checking real-time conditions:,,, and

This weekend is the Texas QSO Party (see, and if I
were in California, to work Texas I would try 15 meters 1900-2230z,
20 meters 1500-0230z, 40 meters any time, but best bet probably
0200-1200z, and 80 meters 0230-1230z.

From Atlanta to Texas try 20 meters 1830-2030z, 40 meters best
2230-0230z, 80 meters 2200-1330z.

From Seattle, 15 meters 1930-2230z, 20 meters 2100-0300z, 40 meters
best 0130-1230z and weakest 1630-2100z, 80 meters 0300-1300z.

From California, 15 meters 1900-2230z, 20 meters 1500-0230z, 40
meters best 0130-1230z and weakest 1700-2130z.  80 meters best

From New York, 20 meters 1500-0030z, 40 meters best 2330-1130z and
weakest 1530-2000z, 80 meters 0130-1030z.

From Ohio, 20 meters 1500-2300z, 40 meters almost around the clock,
but 0630-1030z may be questionable, and best signals 2200-0400z and
1130-1400z.  80 meters 2230-1300z, with strongest signals 0030-0200z
and around 1130z, weakest signals 1600-1930z.

All of these are best guesses worked out with W6ELprop.  Look for
details on using this tool in back issues of this bulletin.

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 20 through 26 were 0, 0, 0, 0, 0, 0
and 0 with a mean of 0. 10.7 cm flux was 66.8, 66.9, 66.7, 66.3,
66.1, 66.2, and 66.5 with a mean of 66.5. Estimated planetary A
indices were 10, 9, 11, 15, 10, 6 and 3 with a mean of 9.1.
Estimated mid-latitude A indices were 6, 7, 10, 11, 7, 5 and 2, with
a mean of 6.9.


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