Register Account

Login Help

ARRL Propagation Bulletin ARLP018 (2009)

ARLP018 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 18  ARLP018
From Tad Cook, K7RA
Seattle, WA  May 1, 2009
To all radio amateurs 

ARLP018 Propagation de K7RA

The data at the end of last week's Propagation Forecast Bulletin
ARLP017 reported daily sunspot numbers from April 16-22 were six
zeros, then 11, when in fact they were zero on every day until April
21, when it was 11, then zero again the next day, April 22.  Just as
many zero sunspot days -- and only one day with a sunspot -- but on
Tuesday, April 21, and not April 22.

We had two additional days with a sunspot this week, Wednesday and
Thursday, April 29-30.  The sunspot number was 15 and 12 on those
days.  But this was another old Cycle 23 sunspot, and it appeared
near the western limb, and may have either faded away completely or
rotated out of view today, May 1.  The data at the bottom of our
bulletin shows seven days, Thursday through Wednesday for the
reporting week, so the sunspot number of 12 for Thursday will appear
in next week's data.

Now that we have all the data for the month of April, it is time to
present our running 3-month average of daily sunspot numbers,
centered on March.

The last time we presented this was four weeks back, in Propagation
Forecast Bulletin ARLP014 on April 3.  We were hoping last Fall that
the sunspot minimum was centered around August 2008, when we showed
the three month average centered on that month with data from July
through September at 1.1.  The following two averages for September
and October were 2.5 and 4.5, but then it began another decline, to
4.4, 3.7, 2.3 and 2.1 for November 2008 through February 2009.

The average daily sunspot number centered on March was just 1.5, so
the decline continues.  Why so low?  From February 1 through April
30 we had very few days with sunspots, in fact only eleven.  There
was never more than one sunspot visible on each of those eleven
days, and the highest sunspot number (an index which does not equal
the number of sunspots) was just 15, and that was this last
Wednesday.  That is not a high sunspot number, but we haven't had
one that high since November 13, 2008 when the sunspot number was

The only days with visible sunspots over the past three months were
February 11-14 and 24-26, March 6-7, and April 21 and 29-30.  That's
it.  And if you add all those sunspot numbers together on those
dates, you get a sum of only 133.  Divide 133 by the 89 days over
those three months, and you get an approximation of 1.49438, or 1.5
to round it up.

Here are the latest 3-month averages of daily sunspot numbers:

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 
Oct 07  3.0 
Nov 07  6.9 
Dec 07  8.1 
Jan 08  8.5 
Feb 08  8.4 
Mar 08  8.4 
Apr 08  8.9 
May 08  5.0
Jun 08  3.7 
Jul 08  2.0 
Aug 08  1.1 
Sep 08  2.5 
Oct 08  4.5 
Nov 08  4.4 
Dec 08  3.7 
Jan 09  2.3 
Feb 09  2.1 
Mar 09  1.5

So if we examine the 3-month averages since January 2007, we see
what we thought was a minimum of 3.0 centered on October 2007, then
another decline to 1.1 in August 2008, and now after rising slightly
it has dropped again, to 1.5.  And of course we have no way of
knowing if next month the number will be lower or higher.

If you look at the sunspot numbers for the three days with sunspots
in April -- April 21, 29 and 30 -- the numbers 11, 15 and 12 only
add up to 38.  Divide that by April's 30 days, and the average is
about 1.267, less than the 3-month average ending yesterday.  So if
we saw the same activity (or lack of it, actually) for May, we could
see another decline at the beginning of June when we look at the
averages centered on April.  If by chance we have no sunspots at all
through the end of May, that average would decline from
approximately 1.494 centered on March to 0.681 centered on April.

Last week's bulletin mentioned the Weak Signal Propagation Reporter
Network site at  This week we
heard from David Witkowski, W6DTW of San Jose, California, who said
that WSPR was developed by Joe Taylor, K1JT, the 1993 Nobel Laureate
in Physics who brought us WSJT and JT65.  David recommends for getting
set up.  Also note the link selections on the left side of that page
for info on WSJT and JT65.

WSJT is a mode for communicating via brief meteor scatter
propagation, and JT65 is useful for moonbounce and troposcatter

Last week's mention of the first signs of early 2009 E-skip season
brought a response from Jon Jones, N0JK, who says most of the
openings have been short, and best for those in Arizona, Texas,
Florida and Central America.  At the start of the season, conditions
are better for the southern tier, but later E-layer openings improve
further north.  He sent a log of 6-meter contacts on April 22, from
2158-2206z on 50.125 MHz.  N0JK (EM17) worked K9NU (EN44), VA2JOT
(FN45ER) worked KI4FCQ (EM72NK), and UT1FG/MM worked K1TTT.

Last night (Thursday, April 30) Rob Geursten, N1KEZ of Beaverton,
Oregon worked some unexpected DX on 20 meter PSK31 at 0545z.  He
copied a Bulgarian special event station, LZ2009KM, working many
European Russians, and Rob worked Wolfgang, DL2MWB in Memmingen,
Germany.  He was surprised to find 20 meters open at this time of
day.  The sunspot number was 12 -- and 15 the day prior -- but a
check with the W6ELprop software shows that with or without
sunspots, communication over that path on the first of May is not
surprising at that time of day, 10:45 PM at Rob's end.  Run the
numbers a month ago, and the path isn't there, but for this late in
the Spring communication becomes more likely.

You can download W6ELprop at  Don't
miss an excellent tutorial for using this software, written by K9LA,
Carl Luetzelschwab at,

Bob Rumsey, KZ5R of Denton, Texas wrote in comparing current
conditions to 45 years ago, during the minimum following Cycle 19.

He writes, "I would like to add a different perspective to the
current solar minimum.  Licensed originally at age 14 in 1962, I
worked the HF bands diligently until I left for college in 1966.
Unless I am mistaken, this was also a period of very low sunspot
activity (there was little understanding of it then) and as a
General class on 50 watts of AM and using a 40 meter dipole and 2
element triband Yagi, I worked little to no DX.  I remember an
opening during a contest in 1965 when I worked G3CAZ and thought I
had walked on the moon."

He continues, "From 1966 to 2006 I kept my license active but other
than a stint with VHF in the 70s did little hamming.  Then after
retiring early and starting my own business, I once again had some
time and felt the tug of the HF bands.  I built up my station and
was amazed at what the technology can now accomplish.  Working
either coast of the US is a day to day occurrence and Europe or Asia
are quite frequent.  So you can imagine my surprise when I began
reading how we were once again in a solar activity downturn while
I'm thinking, 'Wow this is great.'  From November of 2006 when I put
up my vertical disguised as flagpole, I have worked 106 countries
running from 100-1000 watts.  To me this is heaven and of course in
2006 conditions to me where what I remembered as normal.  The
vertical is my primary antenna since I live in a restrictive CC&R

He ends with, "So as you might have guessed, because of the current
technology, I am actually quite happy with the current conditions
and cannot wait to see what true solar activity will bring.  The
proverbial 'kid in a candy store' comes to mind.  Thanks for letting
me provide an alternative viewpoint on today's conditions."

Thanks Bob.  Readers can check out Bob's bio on,

I started in ham radio a few years after Bob -- in 1965 -- and one
big difference is that back then I had a very poor receiver and most
of my attempts at antennas didn't work very well.  To look at the
sunspot minimum back then, use the tool at,  This shows
that the minimum between Cycles 19-20 was probably around the middle
of July, 1964.

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 April 23 through 29 were 0, 0, 0, 0, 0, 0, and
15 with a mean of 2.1.  10.7 cm flux was 70.6, 69.7, 69.4, 69.2,
67.7, 68.8, and 69.5 with a mean of 69.3.  Estimated planetary A
indices were 3, 5, 4, 5, 4, 2 and 3 with a mean of 3.7.  Estimated
mid-latitude A indices were 0, 5, 2, 3, 3, 2 and 3 with a mean of


Instragram     Facebook     Twitter     YouTube     LinkedIn