ARRL Propagation Bulletin ARLP036 (2010)

ARLP036 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 36  ARLP036
From Tad Cook, K7RA
Seattle, WA  September 10, 2010
To all radio amateurs 

ARLP036 Propagation de K7RA

Average daily sunspot numbers for the week rose nearly 13 points to
38.3, and average daily solar flux was up over four points at 78.4.
On September 2 one new sunspot group emerged, numbered 1105.  It
joined sunspot groups 1101, 1102 and 1103.  On September 4, group
1102 faded away, then 1101 and 1103 vanished on September 6.  1105
went over the western side of the Sun by September 9, but a new spot
may be emerging in the northeast.  On September 9 the sunspot number
was zero, and solar flux dropped to 73.7.

The current prediction from US Air Force and NOAA shows a rising
solar flux, 74 on September 10, 75 on September 11-12, 77 on
September 13-14, and peaking at 78 on September 15-16.  This is
lower than the peak of 80 predicted on Wednesday for September 16.
After that a decline in solar flux is expected, then a rise to 80 on
October 2-3.

Looking at the STEREO mission image at
on early Friday morning, there is a bright area south of the solar
equator about to cross the eastern horizon, but we can't tell yet if
this activity will yield sunspots or not.  Currently about 93.4% of
the Sun is within view of the STEREO project, and by the end of
October this will increase to about 96%.

Predicted planetary A index is 5 on September 10-11, 10 and 8 on
September 12-13, 5 on September 14-18, and 8, 12, 8 on 5 on
September 19-22.

Geophysical Institute Prague sees quiet conditions September 10-11,
unsettled September 12, quiet to unsettled September 13, and back to
quiet again on September 14-16.

Chuck Hallett, K4SC of Mesa, Arizona asked, "What are typical
sunspot numbers during the peak of a normal cycle?  I see the
current values, e.g. 25, but have no feel for where that is on a
relative scale."

Current sunspot numbers are quite low, and Cycle 24 is having a long
low start that seems to extend longer as time goes by.  One way to
get an idea of past sunspot numbers and compare them to today is to
look at past issues of this bulletin.

You can view an archive of past propagation forecast bulletins at,

Here is last week's bulletin, showing an average daily sunspot
number of 25.4:

A year ago there were zero sunspots!

You see how you can just change the year at the end of the URL to
get propagation forecast bulletin ARLP035 for every year.  Looking
at the week's average sunspot numbers from that bulletin in every
year from 1997 to 2010 gives us 18.3, 119.3, 90, 135.4, 163.3,
257.1, 122.1, 77.6, 41.1, 21.6, 3.3, 0, 0 and 25.4.

You can see we have to go back 13 years to see a level of sunspot
activity near where it is now, and there is quite a large range of

If you look through the bulletins in 2002, you'll see some big

WM7D has a solar resource page with some historical data:

Another tool for visualizing historical sunspot data is at  You can enter any
date to see what the sunspot cycle looked like for 11 years around
that date. Unfortunately, the links to other sites referenced on
this page don't work.

The Australian government has a page comparing monthly smoothed
sunspot numbers, ranking the fifteen most active months:

These are monthly averaged values, which sum all the sunspot numbers
for a calendar month, then divides by the number of days.  This is a
different value than smoothed sunspot numbers, which represent a
year of data averaged together.

You can see predicted and past smoothed sunspot numbers on page 11
in, which is the
latest issue of the Preliminary Report and Forecast.  Note that this
table shows the current cycle peaking between February and July of
2013 with a smoothed sunspot number of 90.  Back in issue 1701 in
April 2008 the prediction was for a cycle peak from August through
December 2011 with a smoothed sunspot number of 154.  Expectations
are now much lower.

After viewing images of his beam and tower on a residential lot
referenced in last week's bulletin, a number of readers had
questions. How did KD8ID get that big antenna up on that relatively
small residential lot, surrounded by neighbors?  It seems that this
neighborhood has no deed covenants, and KD8ID was able to put up the
antenna without a building permit.  Before the area was wired for
cable television, most people had large outdoor TV antennas on
towers, so neighbors were accustomed to seeing antennas.  KD8ID
reports no RFI complaints from neighbors, perhaps because he has a
directional antenna up high.  He is also very careful about running
high power.

A lot of mail came in concerning the KD8ID antenna and station,
pointing out that the average ham couldn't afford this.  But I think
it is interesting to hear about stations that some individuals have
put a lot of effort into, and for a contester or DXer, his
installation isn't unusual.  But it is a matter of degrees.  The
better the antenna, the more frequently the bands will be open and
the more often you'll be able to work people.

One email from John Shannon, K3WWP of Kittanning, Pennsylvania
indicates he is having fun with simple wire antennas and QRP.  John
writes, "Tad, I must both agree with and take somewhat of an
exception to KD8ID's comments in the last propagation bulletin. I
definitely agree that propagation is there on all the HF bands most
of the time. They sound dead only because no one is transmitting,
only listening. That definitely will make them sound dead even
though propagation might be very good at the time. I often call CQ
on a 'dead' band and wind up with some nice solid rag chew QSOs EVEN
WITH my QRP (or QRPp) and simple wire antennas.

"I think Ron's statements about antennas can be discouraging to many
hams. While it is nice to have super big antennas, that discourages
those who live in apartments, antenna restricted locations, and the
like from even trying the HF bands. Using simple wire antennas such
as a random wire in my attic, and dipoles in my attic or on my porch
roof, I've made at least one QSO using 5 watts output or less each
day since August 5, 1994 or for 5,874 consecutive days as of
9/3/2010. Total QRP QSOs in that time frame - just under 51,500 of
which 13,850 plus are DX from 207 entities.

"Starting with our North American QRP CW Club's (NAQCC) May
challenge of making as many QRPp (less than 1 watt) QSOs as possible
during the month, I've now made at least one QRPp QSO a day using
the above antennas at 930 mW output power. That 'streak' is at 126
straight days and counting.

"See my web site at to get even
more info on what can be done with a very minimal QRP setup. Oh, the
key (pun intended) is to use the best and most efficient of all ham
radio modes - CW. All my QSOs are CW only.

"Please don't discourage your readers by emphasizing the use of big
antenna systems for making QSOs. Big antennas help, but they are
definitely not a necessity, especially if you use CW."

Thanks, John.  I don't think there is anything wrong with talking or
writing about big antennas, wire antennas in your attic, or any
antenna.  It's all part of the big wide world of ham radio, and even
if I don't have enough room or money for a truly big antenna, I
still enjoy hearing about them.

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 an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at,  Find more good
information and tutorials on propagation at,

Monthly propagation charts between four USA regions and twelve
overseas locations are at,

Instructions for starting or ending email distribution of ARRL
bulletins are at,

Sunspot numbers for September 2 through 8 were 52, 54, 53, 58, 24,
16, and 11 with a mean of 38.3. 10.7 cm flux was 77, 77.2, 82.2,
82.1, 79.7, 76.2 and 74.5 with a mean of 78.4 Estimated planetary A
indices were 8, 4, 3, 4, 8, 9 and 10 with a mean of 6.6. Estimated
mid-latitude A indices were 5, 3, 0, 4, 6, 7 and 8 with a mean of