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ARRL Propagation Bulletin ARLP036 (2009)

ARLP036 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 36  ARLP036
From Tad Cook, K7RA
Seattle, WA  September 4, 2009
To all radio amateurs 

ARLP036 Propagation de K7RA

This week we saw another one of those fast-disappearing sunspots.
It lasted just two days, over the last day of August and the first
of September.  No other sunspots were observed during the month of

The monthly average of the daily sunspot number, January through
August 2009, is 2.8, 2.5, 0.8, 1.3, 4, 6.6, 5.1 and 0.4.

The three-month moving averages of daily sunspot numbers for October
2008 through July 2009 were 4.5, 4.4, 3.6, 2.2, 2, 1.5, 2, 4.2, 5.2
and 4.  This takes into account all the daily sunspot numbers for
September 2008 through August 2009, and those numbers are for the
center months of each of those three month moving average periods.

The latest figure, for July 2009, is an arithmetic average of all
daily sunspot numbers for June through August.  The previous figure,
for June, is an average of daily sunspot numbers for May through
July.  In other words, sum all the daily sunspot numbers from May 1
through July 31, which equals 478.  Divide by 92, which is the
number of days in those three months, and it equals approximately
5.196, or 5.2 rounded off.

For June and July we saw the moving average drop from 5.2 to 4, and
if September has no sunspots after the one on September 1, then the
three-month average centered on August will be 2.

So what is coming up in the near term?  Continued low solar flux and
possibly no sunspots.  Geophysical Institute Prague predicts quiet
to unsettled conditions for September 4 and 8.

We received many tips and comments this week about the lack of
sunspots, and a link at, to an
article titled, "Are Sunspots Disappearing?"

It concerns the work of Livingston and Penn at the National Solar
Observatory in Tucson, and their observation that magnetic fields
from sunspots are declining.  It is important to note that most of
their measurements are after the peak of Cycle 23, so this may be
normal during the decline of a cycle, not just this one.  Also, when
they say there may be no sunspots by 2015, this is an extrapolation.
Since we do not know what has happened in previous cycles regarding
this more accurate measurement of magnetic fields from sunspots, it
may be unrealistic to assume that the trend will continue.

NW7US interviewed Dr. Penn this week in his podcast, which you can
download from  Very interesting
interview with lots of details on his research.

Regarding sunspots disappearing, check out the comments from K6SGH
on his web page,

An interesting comment came from Jim Williams, K5NN of Wichita,
Kansas.  Jim wrote, "As an old retired Electrical Engineer and a ham
dating back to 1952, I'm wondering what the explanation for
consistent long skip might be. I have been involved in an informal
net on 75 meter SSB for close to 50 of those years (2 uncles and
others, lots of silent keys now) before going to work-about 7AM
central time. We never used to have consistent problems with long
skip, now most mornings short skip is 200 miles. As I have been
active through several sunspot minimums, the extended periods of
long skip around daylight was never such a problem. Lately it has
taken a kilowatt to be just above the noise on a hundred mile path,
the path normally has been good, even at 100 watt level. Is a good
plausible explanation in existence for these conditions?"

This brings to mind an August 2007 email from Jerry Reimer, KK5CA of
Spring, Texas.  Jerry mentioned that short skip on low frequencies
depends on NVIS (Near Vertical Incidence Skywave) propagation.  The
propagation out to 100 miles depends on the high angle component of
the antenna radiation bouncing or refracting off the ionosphere
overhead.  Longer skip depends on lower angle radiation.  Jerry
mentioned that for reliable short skip propagation, the frequency
used should be only 50-80 percent of the fMUF.

Recent fMUF values from ionosonde data may be found at  If I click on
the Boulder (Colorado) data, I see that over the past day the fMUF
above Colorado may not be high enough to support short skip on 75

Another source of real time info are the HAP (Hourly Area
Predictions) charts at
Select a location from the drop down menu, and you see a map showing
propagation for various frequencies from that location.

Go to for more information about

We got a report this week from Luke Steele, VK3HJ, in Benloch,
Victoria, Australia.  He will soon see the Spring equinox down under
(our Autumnal Equinox in the Northern Hemisphere is September 23,
nearly three weeks from now), and note at the end of his comments
that he echoes K5NN regarding 80 meters.

"Just thought I'd drop a line and offer a DX perspective from my
modest station in central Victoria, 50 miles NW of Melbourne."

"My main antenna here is a 520 foot doublet at 60 feet, with open
wire to the shack and a 1/4 wave vertical for 40m."

"Conditions the past few months have been very quiet, with very
little happening on 20m and up, although I have still been working
DX on CW and PSK most evenings (0800-1400z). There are nearly always
Russians to be seen on 20m PSK afternoons and evenings here."

"40 and 30m provide continuing interest, particularly CW and PSK.
Contacts to the Pacific Islands and S Asia and JA are available in
the evenings when I get on the air. Some Indian Ocean contacts to be
had, recently with VQ9JC and VQ9LA on Diego Garcia on 20 and 40m,
and 4S7NE in Sri Lanka."

"75m SSB looks average for this time of year with USA on most
evenings. 40m CW to USA is mostly good, and SSB is light. I've also
been hearing some North America on 160m CW most evenings, and have
worked a couple. Top band OK out to Western Australia, Queensland
and the western Pacific Islands (out to about 2500mi)."

"Nothing much from Europe, Africa, South America and the Caribbean
for some months."

"Local club nets on 80m in the evenings have sometimes been
difficult, over the past few months with close stations weak, those
beyond about 500mi loud. There's also DX to be had in the mornings
here, but I usually miss that, not being a 'morning person'!"

"So, there is still DX to be had, but operating modes and methods
need to change to suit."

Thanks, Luke!

Bob Karpinski, WB8B from Clinton Township, Michigan has been having
fun running QRP on 17 meters.

Bob wrote, "There was a very sporadic opening with very good signals
from the far western edge of EU on 17m from 2300-0000z from
Michigan. CT1JOP was worked on 17m CW with only 1 watt on 8/27/09
2330z! He lowered his power to 5w during the QSO and we had a 2-way
QRP contact with 559 signals."

Steve Ickes, WB3HUZ of Lightfoot, Virginia wrote: "Despite the lack
of sunspots, I've been enjoying world wide DX on 40 meters daily. 80
meters has been more active in the last few weeks with very strong
signals (5-9+20) from many stations out of Europe. It can only get
better as the static begins to subside with fall coming."

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 web page 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

Instructions for starting or ending email distribution of this
bulletin are at

Sunspot numbers for August 27 through September 2 were 0, 0, 0, 0,
12, 12, and 0 with a mean of 3.4.  10.7 cm flux was 67.7, 67.9, 68,
67.2, 68.3, 69.1, and 68.2 with a mean of 68.1.  Estimated planetary
A indices were 5, 2, 2, 19, 5, 4 and 3 with a mean of 5.7.
Estimated mid-latitude A indices were 4, 2, 2, 12, 5, 2 and 2 with a
mean of 4.1.


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