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ARRL Propagation Bulletin ARLP009 (2010)

ARLP009 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 9  ARLP009
From Tad Cook, K7RA
Seattle, WA  March 5, 2010
To all radio amateurs 

ARLP009 Propagation de K7RA

Two new sunspot groups appeared on March 1, numbered 1052 and 1053.
The total number of sunspot groups appearing over the last month is

Looking at our 3-month moving average of daily sunspot numbers, the
latest for December-January-February is 22.4, for the period
centered on January.  The average daily sunspot number for the month
of February was 31.  The fact that this is higher than the latest
3-month average is a welcome trend.

The current 3-month average centered on January 2010 is very close
to the 3-month average centered on January 2007, which was 22.7.
That moving average has not been as high since.  In fact, the
closest it has been was February 2007, at 18.5.  It was all downhill
from there, and that average was below 10 from September 2007
through October 2009.  It now looks like we saw three minimums,
which is why it was so easy to err when trying to locate the bottom.
Several times we hit some low number, decided that things were
improving, and then a few months later hit it again.

The three minimums were 2.97 in October 2007, 1.1 in August 2008,
and 1.5 in March 2009.

The three month moving average centered on January 2008 through
January 2010 was 8.5, 8.4, 8.4, 8.9, 4.9, 3.7, 2, 1.1, 2.5, 4.5,
4.4, 3.6, 2.2, 2, 1.5, 2, 4.2, 5.2, 4, 4, 4.6, 7.1, 10.2, 15.2 and

The ARRL International SSB DX Contest is this weekend, and it isn't
really certain whether there will be sunspots visible through the
whole of the contest.  Sunspot groups 1051, 1052 and 1053 will soon
rotate over the Sun's western limb.  Looking at images from the
STEREO spacecraft (, there is a
magnetically complex area visible in the upper left quadrant facing
Earth, but no sunspot has emerged there.  Looking beyond the horizon
the only really active area (bright white contrasted against green)
appears to be emerging from the far side blind spot in the southern
hemisphere.  That could be five days away from emergence over the
eastern horizon.

The blind spot of the STEREO mission incrementally recedes.  On
March 1, 88.1% of the Sun was visible to the craft, on April 1,
88.5% should be visible, and 90% visibility will occur some time in
June.  For the first of December 2010, January 2011 and February
2011 visibility should be 97.4, 98.7 and 99.8%.  After that, the two
spacecraft continue their journey, but the blind spot shifts to the
Earth-side of the Sun, which of course we can see directly.

Earlier this week the prediction for the weekend showed higher
activity.  Go to and click on
March 1.  Note the solar flux values for today, tomorrow and Sunday
(March 5-7) show predicted solar flux at 84, 86 and 90, with flux
staying at 90 through March 13.

Now click on March 4, which was the latest report available by the
time this bulletin was written early Friday morning, and for the
same period it has shifted way down to 82 straight through March 12.
You can go back to that site to get the updated forecast after 2000z
(but often after 2100z) today, and on subsequent days.

The same forecast shows quiet geomagnetic conditions with planetary
A index of 5 until March 15 and 16, when it rises slightly to 8 and
7.  Geophysical Institute Prague predicts quiet conditions for March
5 through 11.

K9LA pointed out a problem with the description of effective sunspot
numbers from in last week's Propagation Forecast Bulletin

At we see a plot of SSNe, or
effective sunspot number, which is derived from multiple ionospheric
sounders.  The ionosonde data used is foF2, which is the critical
frequency of the F2 layer.  It is the maximum frequency that can be
reflected back from the F2 layer by a vertically incident beam.  The
smoother heavy line in the upper SSNe graph uses 24 hours of foF2
data, and the lighter and less smooth line uses 6 hours of data.
Using a longer period of data makes the 24 hour line smoother,
because it behaves more like a moving average, responding less to
short duration changes.

This page, gives a more formal
definition of the derivation of effective sunspot number. shows a comparison of SSNe,
actual observed sunspot number, and SSNf, a sunspot number derived
from the 10.7 cm solar flux.  The formula toward the bottom shows *
as multiplication, and SSNf**2 I believe means SSNf raised to the
second power, a way of showing exponents using conventional

The formula shows a relationship between solar flux and SSNf, but is
not set up to solve for SSNf using solar flux.  So to test it I
entered some sunspot numbers into a spreadsheet, and then calculated
10.7 cm flux using the formula.  The relationship came out roughly
in line with the same values entered into W6ELprop, which always
shows flux values when entering sunspot numbers, and sunspot numbers
when flux values are used.

W6ELprop introduces a variation based on date, because of our
elliptical orbit around the Sun.  At you
can see a column for observed solar flux, and another for adjusted
solar flux.  The adjusted value factors for variations due to
Earth's orbit.  Note certain dates when the adjusted and observed
values are equal.  Using those dates with W6ELprop and entering
sunspot numbers results in flux values equal to data produced by the
formula referenced above.

Many reports on good 10, 12 and 15 meter conditions came in
recently, and K9IL wrote last week: "From NW Tennessee in the last
10 days I've picked up 40 new countries from all continents. Using
400w and a homemade 2 el Yagi at 30'. I worked my 1st JA ever on
12m. Worked 5R, VQ9 almost the maximum distance away. No VU yet but
12m has been great."  Thanks, Bob.

Richard Vincent, KR7R, lived in Seattle, but retired some time back
to Chiang Rai, way up in Northern Thailand.  He sits 30 miles from
the Burmese border to the northwest, and about the same distance
northeast to the Laotian border.  From there he operates HS0ZFQ.

Richard writes, "I was complaining about PSK being so hard on twenty
meters, then on February 25, I decided to look at 15 meters.
Without any sweat whatsoever I proceeded to work 5R8FL (Madagascar),
EK1KE (Armenia), OH4TI, DL6TG, and HA1AD (Hungary) to the PSK log.
When OH4TI came back he just said WOW? He was as surprised as I

"Early the next morning I hooked up with Bob, K6MBY, in Sequim,
Washington, and we talked for about twenty minutes with good copy. I
run 30 watts to the quad and he was running about the same. After
that it was anticlimactic, YL3GP (Latvia), ZS2I (South Africa) and
IZ3AX in Padova Italy. So in two days I added another nine
countries, all on 15 meters. So tell the boys that from about 0500Z
to about 0800Z, noon to 3PM our time, that 15 is good. It fades for
the west coast, at least it did yesterday, at 0100Z."

It looks like the best time for Richard, who is around 19.91 N
latitude, 99.83 E longitude, to work Sequim, Washington on 15 meters
would be around 0000-0130z next week.  But 17 meters should give a
better shot.  For Richard, working Southern California on 15 would
be best around 0000-0230z, and 0630-1400z to Europe.

An email arrived from Peter Burokas, KL1HB who has a PO Box in
Fairbanks, Alaska, but lives about 65 miles north in grid square
BP55.  With no internet access, he sends email via Winlink.  He
lives way off the grid with no commercial electricity, running
water, or TV.  His email said he worked his first 10 meter contact
recently, but nothing about where the other station was located. But
don't miss his page at  It must be a
challenge to harness solar power at 135 miles south of the Arctic
Circle.  I see that on December 22, according to his grid square,
his sunrise was at 2023z and sunset at 2326z.  I wonder how many
degrees above the horizon the Sun rose?  On June 22 the Sun sets at
0827z and rises 3 hours later at 1129z.  He must charge his
batteries with his solar cells in the Summer.

Ian Drury, W0IMD/G0FXQ in Elbert, Colorado wrote, "I was switching
between 12/10m on 18 February. I called an EA8 and a CT1 on 10m, S9
both ways. On 12m, worked GM and ZB2, both S9 again. This occurred
between 1716-1728z."

"Openings to South America are pretty commonplace on both those
bands from here in CO, but that was the first time I worked EU on
both bands with signals truly that strong. I am still amazed and
excited by that." In a later email Ian indicated he was using CW.

And finally, it is fun getting messages from new hams who haven't
experienced sunspots before.  Of course, the sunspot activity we're
now seeing isn't much, but it seems great compared to the drought
over the past few years.

Here are thoughts from Randy Cook, K6CRC of Los Altos, California.

"I am a relatively new ham, passed the Tech in 2006, the General in
2007, and the Extra Class this January.  Due to all the usual
reasons, I have not been on the air as much as I'd like. I also have
been in the hobby during one of the worst sunspot droughts in a long

"I have to admit I have been very skeptical of the claims by old
timers of 'working the world with 5 watts' during high sunspot
activity.  Euro QSOs are not a regular occurrence for me - with the
exception of contests, I do not have many QSOs outside North
America. The few I do hear are usually the big guns with pictures of
their incredible antenna arrays on"

"However, today was amazing. I am thinking maybe the OTs haven't
been breathing too much solder smoke."

"I was short on time this morning, so I decided to just spin the
dial and listen for a few moment starting at about 1500z. Even with
my modest roof mounted vertical, it was solid Europeans on 15 meters
in Northern California. I was rewarded with a number of interesting
QSOs, including a German ham adjusting a portable 20m antenna and
looking for local signal reports."

"The 'wow' moment came when I heard a weaker, but copyable French
contest station, F6KHM, CQ'ing for North America with a 'QRP' suffix
and '6 watts.' As an experiment, I cranked my Elecraft K3 output to
under 10 watts, and returned the call. We had a good conversation
and the band held up for about 10 minutes. Solid copy and 55 signal
reports. Fortunately his English was significantly better than my

"All and all, an interest morning. I have not had this type of
experience before. I hope this continues."

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 February 25 through March 3 were 30, 26, 26, 13,
36, 39, and 39 with a mean of 29.9. 10.7 cm flux was 82.7, 80.5,
78.6, 78.1, 77.9, 79.4, and 80.4 with a mean of 79.7. Estimated
planetary A indices were 2, 2, 2, 2, 5, 4 and 6 with a mean of 3.3.
Estimated mid-latitude A indices were 2, 1, 0, 2, 4, 3 and 5 with a
mean of 2.4.


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