ARRL Propagation Bulletin ARLP008 (2006)

ARLP008 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 8  ARLP008
From Tad Cook, K7RA
Seattle, WA  February 24, 2006
To all radio amateurs 

ARLP008 Propagation de K7RA

More zeroes! A string of zero-sunspot days re-appeared this week, a
pattern we'll likely see repeated over the next year, but for longer
periods. Average daily sunspot numbers compared to last week dropped
nearly two points to 7.1. On February 20 and 21 a gust of solar wind
hit Earth, causing a moderate rise in geomagnetic indices and
visible aurora way up north. A small coronal hole on our sun's
equator was the source.

Over the next week don't expect a rise in sunspot numbers. You can
take a look at recent numbers, updated daily at, Check for geomagnetic

A solar wind from a coronal hole is expected to cause unsettled
conditions for Friday and Saturday, February 24-25.  Geophysical
Institute Prague expects unsettled conditions for February 24, quiet
to unsettled on February 25, quiet February 26-27, and quiet to
unsettled on February 28-March 2.

We receive a steady stream of mail inquiring about the magnitude of
the next solar cycle, and the end of this one. Steve Stutman,
KL7JT/1 in the Boston area said he'd heard somewhere that the rise
of the next solar cycle should be modest. I poked around, and found
this interesting link for solar cycle 24:

With twenty-three recorded sunspot cycles, there isn't a huge amount
of data to analyze. And so you can see on this site, various
approaches are put forth, which the users believe have worked in the
past. I think most of us would prefer Hathaway's prediction, which
is the first one listed under Predictions of Cycle 24. We would
prefer it, because it is the most optimistic.

Don't miss this graphical presentation of data from the current
cycle 23: Also, see a nice
visualization of all recorded solar cycles at You can see from
these graphs why cycle 19 in the late 1950s is recalled with such

I became interested in ham radio as a young boy in 1963, got my
license in 1965, and not only was solar activity low during the
mid-1960s, but cycle 20 peaking in the late sixties was a real
stinker in comparison to the recent one. Of course all of the older
hams (just about everyone, since I was 12 at the time) had
experienced cycle 19, and I hadn't. My only recollection of cycle 19
was as a small boy in Reedley, California.

My father was a biologist, taking a few years off to earn money for
school selling insecticide to farmers before returning to Berkeley
for his PhD. My dad had a company car, with a long whip antenna on
the back connected to a low-VHF business-band FM two-way radio
(probably 30-40 MHz). I recall him talking about being unable to
raise the head office in Fresno, but someone in Texas was able to
relay for him, and something about sunspots. Around that time hams
were living it up on 10-meter AM, working the world with low power.

We don't have many sunspots now, so the MUF (maximum usable
frequency) tends to stay low. But we do have quiet conditions, and
the CQ 160-Meter SSB contest this weekend isn't bothered by low MUF.

Finally, Cap Cox, W4AMW of Owensboro, Kentucky wrote in about the CW
portion of the ARRL International DX Contest, which was last
weekend, and conditions in general:

"Saturday morning around 1000-1200z I worked Japan, Russia, Western
Europe and could hear VT and CO all about the same time on 40
Meters. That night I worked Japan and Switzerland on 80. Sunday
during the day 20 was open into Europe and Africa all day and even
10 Meters lit up into Central and South America in the early
afternoon. I'm running a hundred watts into a Windom. I kept looking
at my calendar to make sure it wasn't 2013 already. Wow!"

Cap goes on to say, "I guess it helps to have a couple of thousand
operators on all the HF frequencies pushing the ethereal envelope in
order to know what conditions are really like under the
circumstances. I can get by with 'poor' bottom of the cycle
conditions like these for a long time, maybe even until the next
'peak' arrives."

Thanks, Cap.

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 and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at, An archive of past
propagation bulletins is found at,

Sunspot numbers for February 16 through 22 were 27, 23, 0, 0, 0, 0
and 0 with a mean of 7.1. 10.7 cm flux was 79.2, 79.2, 78.5, 76.5,
76.2, 75.9, and 76, with a mean of 77.4. Estimated planetary A
indices were 8, 4, 2, 6, 20, 17 and 12 with a mean of 9.9. Estimated
mid-latitude A indices were 7, 2, 2, 5, 9, 15 and 11, with a mean of