ARRL Propagation Bulletin ARLP042 (2008)

ARLP042 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 42  ARLP042
From Tad Cook, K7RA
Seattle, WA  October 10, 2008
To all radio amateurs 

ARLP042 Propagation de K7RA

A familiar sight appeared this week, as sunspot 1003 emerged for one
day, then was gone. 1003 was a new Cycle 24 sunspot, based on its
magnetic polarity and high position in our Sun's southern
hemisphere, and like all the other recent sunspots, it was short

Geomagnetic conditions were still quiet, although a coronal hole
wind stream having maximal effect centered on October 3 caused
unsettled conditions.  At mid-latitudes the effect was slight, with
a middle-latitude A index for October 2-4 at 11, 10 and 8.  Toward
the poles conditions were more active, as expected.  In Fairbanks,
the college A index for those same days was 26, 32 and 17.

With northern hemisphere hours of darkness expanding and geomagnetic
stability the norm, this is a good time to use the lower part of the
HF spectrum -- 160, 80 and the relatively new 60 meter band.

Last week's Propagation Forecast Bulletin ARLP041 mentioned Mike
Reid, WE0H and his experimental operation on 500 KHz. This week he
mentioned that "LF and MF propagation seem to have inverted
propagation from the HF bands." He notes that on October 2, 40
meters seemed dead, but 600 meters came alive.  You can learn more
about WD2XSH and the ARRL 600 Meter Experimental Group at,

Regarding noctilucent clouds and VHF/UHF propagation, Roger Swickis,
VE7BZR of Gibsons, British Columbia recalls seeing them in
Churchill, Manitoba in 1968 and being quite impressed at the time.
He added, "I saw them again in the early 1970s while working the
midnight shift as a Radio Operator/Weather Observer at Kenora,
Ontario.  Early that morning I heard Winnipeg Tower (at about 120
miles) testing on 121.5 and 243.0 MHz and we exchanged signal
reports.  I always wondered if the long propagation was related to
the NLC."

For October 10 to 17, the U.S. Air Force Space Weather Operation
predicts planetary A index at 5, 5, 15, 10, 5, 5, 5 and 5.  Over the
same period Geophysical Institute Prague predicts quiet conditions
today, October 10, unsettled October 11-12, quiet to unsettled
October 13, and quiet again October 14 to 16.

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 October 2-8 were 0, 0, 12, 0, 0, 0, and 0 with a
mean of 1.7.  10.7 cm flux was 66.3, 67.2, 66.6, 67.4, 67.2, 66.7,
and 67.7 with a mean of 67.  Estimated planetary A indices were 12,
13, 11, 4, 4, 3 and 2 with a mean of 7.  Estimated mid-latitude A
indices were 11, 10, 8, 3, 3, 1 and 2 with a mean of 5.4.