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ARRL Propagation Bulletin ARLP017 (2008)

ARLP017 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 18, 2008
To all radio amateurs 

ARLP017 Propagation de K7RA

We saw a string of zero-sunspot days over the past couple of weeks,
but this week saw a brief but significant sunspot lasting only a
couple of days.  Sunspot 990 emerged as a tiny speck over April
14-15, but it was a real live solar Cycle 24 spot.  Not only was the
polarity of this region correct for the new cycle, but it was far
north above the Sun's equator, which is what we expect for a sunspot
from an emerging solar cycle.  The only previous Cycle 24 activity
was close to the solar equator.

For some unknown reason there were no mid-latitude geomagnetic
readings from the Fredericksburg Virginia magnetometer on April 10,
so I estimated the A index for that day as 6.  This was done by
looking at the Boulder Colorado readings for April 9-11 and the
Fredericksburg readings for both April 9 and April 11.

Fredericksburg is about 1500 miles east of Boulder, and about 2.4
degrees south in terms of latitude.  Each location produces a
mid-latitude K and A index.  The Fredericksburg numbers are reported
at the end of each ARRL Propagation Forecast Bulletin, and the
Boulder numbers are what you hear on WWV at 18 minutes after the
hour when they give the Geophysical Alert Message.

You can see the current message at, and look through an
archive of them at,  NOAA predicts
quiet geomagnetic conditions over the next few days, with
geomagnetic upset occurring on April 23.  The chance of returning
sunspots increases beginning April 20, and the best bet for more
spots is April 26-28.

Geophysical Institute Prague predicts quiet conditions April 18,
quiet to unsettled April 19, quiet April 20, quiet to unsettled
April 21, active April 22-23, and unsettled to active April 24.

Stan Whiteman, W1MDZ of Danforth Maine wrote to say he has set up a
telescope with the proper filters for viewing sunspots.  Of course,
now that he has it finally set up, there were no sunspots to see.
Danforth is a community in East Central Maine, across Grand Lake
from New Brunswick, Canada.  Stan turns 87 this year.  Stan didn't
mention this, but I happen to know that he was stationed in Japan
after World War II, and got to meet Dr. Hidetsugu Yagi, the
originator of the Yagi antenna.

Last week we mentioned the storm brewing a couple of months ago when
a daily business publication ran an article suggesting the Sun is on
the verge of a Maunder Minimum, a many decades long period with very
few sunspots.  They quoted Dr. Kenneth Tapping of Canada's Dominion
Radio Astrophysical Observatory in Penticton British Columbia --
quotes that he says are incorrect and misleading.

Ken has produced a very good response, complete with graphs
demonstrating that this minimum we are currently experiencing
between cycles is nothing unusual.  You can get a copy via email by
sending a request to,  Every email sent to
this address, no matter what the content, will receive a copy of Dr.
Tapping's report via return email.

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 10 through 16 were 0, 0, 0, 0, 11, 12, and
0 with a mean of 3.3.  10.7 cm flux was 67.9, 67.1, 68.2, 69.3,
68.5, 69.2, and 69.5 with a mean of 68.5.  Estimated planetary A
indices were 8, 4, 11, 7, 2, 5 and 15 with a mean of 7.4.  Estimated
mid-latitude A indices were 6, 3, 8, 6, 2, 3 and 9, with a mean of


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