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ARRL Propagation Bulletin ARLP045 (2007)

ARLP045 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 45  ARLP045
From Tad Cook, K7RA
Seattle, WA  November 2, 2007
To all radio amateurs 

ARLP045 Propagation de K7RA

Average daily solar flux and sunspot numbers were unchanged from
last week.  The average sunspot number was easy to figure, since
there were none.  Average daily solar flux was essentially the same,
67.3 and 67.2.  Since this is a new month, it is time to go over
some monthly sunspot averages.  But more about sunspots later.

A big surprise this week was last weekend's 15 meter activity during
the CQ World Wide DX Phone Contest.  We've recently reported 10 and
15 meter activity that seemed surprising for the bottom of the solar
cycle, but openings on Saturday and Sunday, October 27-28 seemed to
have little precedent.

N3RD and KC1XX worked 139 and 150 countries, respectively, in the
contest, all on 15 meters.  All this with still no sunspots.

Dave Hawes, N3RD of Phoenixville, Pennsylvania (about 25 miles
northwest of Philadelphia) wrote, "The band opened strongly to
Europe both mornings, but from the East Coast, there were virtually
no eastern Asians to be had, with only one JA logged here. Several
VKs and ZLs made it through, as did A35, V7, KH6, and FO. KL7RA
squeaked through with an ESP level signal. Of course, the N-S path
provided many strong signals, and there was a good showing from
Africa and the Middle East as well. If this is what no sunspots is
like, I can hardly wait for some to show up.  There's no meters like
15 meters!"

I should point out though that N3RD used an array of three stacked
5-element Yagis.  And KC1XX, the station that worked 150 countries
on 15 meters, has an even more impressive antenna installation,
which you can see at,

We've commented recently that the recent 10-meter activity is a
surprise at the bottom of the cycle, but another opinion was put
forward by Bob Adams, W7UH of Bryantown, Maryland.  Regarding
north-south propagation on 10 meters, he wrote, "In the 55 years I
have been listening and working 10-meters, this is not unusual. In
fact it's quite common. People should pay more attention to their
logbooks and their memories. North/South propagation is quite common
on 10 meters from all parts of the U.S. to Central and South America
and the Caribbean."

Carl Luetzelschwab, K9LA commented, "I think Bob, W7UH summarized
his 10-meter experiences very well. I think the bands are open a
heck of a lot more than we realize - and when a contest comes along,
it really shows."

Carl also commented that, "we have to remember that sunspots are not
the cause of F2 region ionization - it's radiation at wavelengths
between 10 and 100 nm (nanometers). Sunspots, just like 10.7 cm solar
flux, are proxies for the true ionizing radiation."

Carl continued, "The closest measurement we have is the GOES X-ray
data at 0.1 to 0.8 nm in the Weekly Report put out by the Space
Weather Prediction Center, and those wavelengths impact the D
region. When the next report comes out Tuesday evening, we'll see if
there was any increased radiation in the 0.1 to 0.8 nm band - that
could indicate we had increased radiation in the 10 to 100 nm band."

There wasn't the expected increased radiation at .1 to .8 nm.  Carl
wrote, "If there wasn't an increase, it was probably a combination
of moving into northern hemisphere winter and some geomagnetic
activity that enhanced the mid and low altitude F2 region."

Jack Emerson, W4TJE of Fancy Gap, Virginia works 15 meters with a
7-element Yagi at 100 feet and a 5-element Yagi at 75 feet.  He
wrote, "Maybe my set-up on 15 meters is giving me a head-start, but
over the past month many other East Coast stations have discovered
that 15 has reawakened as well. What we have been hearing is much
more than the seasonal improvement we always get this time of year,
though that surely is helping. Listening to the band over the past
month at my QTH, you would think we were closer to the top than to
the bottom.  I'm not exaggerating. I have filled log page after log
page with Europeans and Mid-East stations on phone and CW. But
hearing the JA on 15m this past weekend, with the solar flux at 68 I
think, that takes the cake. Though he was too weak for me to work, I
did hear stations as far east as W9 working him."

Here at K7RA, I went out mobile on Sunday with a set of monoband
whips, and worked several Caribbean and South American stations
before discovering that I was using the 10 meter instead of the 15
meter antenna.

We received many other reports from people surprised at the
no-sunspot propagation on 15, as well as 10 and 12 meters.  It may
be that we're experiencing a combination of factors, including DX
stations with great antennas, and also spotting networks that bring
many stations on the air when an opening occurs.  All of this
conspires to contrast our on-air experiences with the remembered or
misremembered activity of 11 or 22 years ago.

Below is the latest update on our 3-month moving average of daily
sunspot numbers.  We've been tracking this in 2007 to help us spot
trends that might indicate the bottom of the solar cycle.

Dec 05 40.6 Jan 06 32.4 Feb 06 18.1 Mar 06 27.7 Apr 06 38.5 May 06
39.7 Jun 06 28.9 Jul 06 23.3 Aug 06 23.5 Sep 06 21.2 Oct 06 24.1 Nov
06 23.1 Dec 06 27.3 Jan 07 22.7 Feb 07 18.5 Mar 07 11.2 Apr 07 12.2
May 07 15.8 Jun 07 18.7 Jul 07 15.4 Aug 07 10.2 Sep 07  5.4

The average for August, September and October, centered on
September, at 5.4 is the lowest yet for this side of cycle 23.  This
number was derived by adding together all the daily sunspot numbers
for those three months, then dividing the sum (492) by the number of
days, which is 92.

The straight monthly sunspot number averages for this year, January
through October, are 28.2, 17.3, 9.8, 6.9, 19.8, 20.7, 15.6, 9.9,
4.8 and 1.3.  October's average is lower than September and October
of 2006, during the minimum between cycles 22 and 23.  The monthly
averages for August through November, 1996 were 20.7, 2.9, 2.3 and

So what's next?  ARRL CW Sweepstakes is this weekend.  No
geomagnetic upsets are expected, but no sunspots either.  This is a
domestic instead of a DX contest, with the object being to contact
as many stations in as many ARRL sections as possible.  There is no
provision for working a station more than once by switching bands,
so whichever band offers the highest rate at any time is the one to
be on.  You can go to, to read the
contest rules.

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 October 25 through 31 were 0, 0, 0, 0, 0, 0 and
0 with a mean of 0.  10.7 cm flux was 67.1, 67.5, 67.1, 67.5, 67.1,
67.2, and 67.1 with a mean of 67.2. Estimated planetary A indices
were 20, 14, 10, 7, 14, 10 and 4 with a mean of 11.3. Estimated
mid-latitude A indices were 10, 10, 8, 4, 8, 10 and 3, with a mean
of 7.6.


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