ARRL

ARRL Propagation Bulletin ARLP041 (2008)

SB PROP @ ARL $ARLP041
ARLP041 Propagation de K7RA

ZCZC AP41
QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 3, 2008
To all radio amateurs 

SB PROP ARL ARLP041
ARLP041 Propagation de K7RA

The latest sunspot appearance reported last week seems to follow the
pattern emerging for most of 2008.  A spot will appear for one or
two days, and then suddenly it is gone.

Last week's Propagation Forecast Bulletin ARLP040 mentioned the
solar wind being at an all time low.  This week NASA announced that
2008 so far is the "blankest year of the space age," with over 200
spotless days.  The minimum following Cycle 18 in 1954 had 241 days
without sunspots, and it preceded the solar max in 1959 for Cycle
19, which had the highest sunspot numbers on record.

Read the NASA article at,
http://science.nasa.gov/headlines/y2008/30sep_blankyear.htm.

With September passed, we now can calculate the 3-month average of
sunspot numbers centered on August, which was 1.1.  Compare that
with 3 month averages going back to June 2006.

Jun 06 28.9
Jul 06 23.3
Aug 06 23.5
Sep 06 21.2
Oct 06 24.1
Nov 06 23.1
Dec 06 27.3
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
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
Jun 08  3.7
Jul 08  2
Aug 08  1.1

Randy Crews, W7TJ of Spokane, Washington commented that extended
periods of quiet Sun make propagation more predictable, but zero
sunspots affects all bands, not just 15 meters and higher
frequencies.  Even 80 meters is different.  After sunset when
residual ionization from the Sun is gone, 80 meters suffers.  He
believes we are seeing a double bottom (October 2007 and now)
following the double peak of Cycle 23.

Two weeks ago, on September 19, Michael Reid, WE0H of Saint Francis,
Minnesota mentioned his experimental operation on 600 meters (500
KHz) as WD2XSH/16.  Mike said the low solar activity and quiet
geomagnetic conditions make this part of the spectrum quite
attractive for long distance propagation.  During the previous week
he and other FCC Part 5 experimental stations were beaconing and
getting reports from all over, typically 1000 miles distance.

Early last Friday morning (September 26) George Hrischenko, VE3DGX
of Zephyr, Ontario noticed a number of UHF and high VHF (175-220
MHz) television stations coming in from a long distance away.  He
didn't say where the signals were from, but figures it must be from
ducting.

In response to last week's mention of noctilucent clouds and UHF
propagation, Ken Beck, WI7B of Kennewick, Washington sent a copy of
the scientific paper by Bellan referenced in the article in Science
Daily, published in the Journal of Geophysical Research, vol 113,
D16215.  He notes the article mentions propagation from 50 MHz to 1
GHz, so this may be a useful propagation mode for 6 meters as well.

Click on http://www.agu.org/pubs/crossref/2008/2008JD009927.shtml to
read an abstract of the article, and note there is a link on that
page providing access to the full article.

Patrick Dyer, WA5IYX of San Antonio, Texas sent a link to a 1968
article in Soviet Life about noctilucent clouds and experiments run
by a Latvian teenager.  Read about it at,
http://www.qsl.net/wa5iyx/es-nlc.htm.

If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at,
http://www.arrl.org/tis/info/propagation.html.  For a detailed
explanation of the numbers used in this bulletin see,
http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
propagation bulletins is at http://www.arrl.org/w1aw/prop/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at http://www.arrl.org/qst/propcharts/.

Instructions for starting or ending email distribution of this
bulletin are at http://www.arrl.org/w1aw.html#email.

Sunspot numbers for September 25 through October 1 were 0, 0, 0, 0,
0, 0, and 0 with a mean of 0.  10.7 cm flux was 68.2, 67.7, 67.3,
67, 66.8, 66.2, and 65.8 with a mean of 67.  Estimated planetary A
indices were 4, 4, 2, 3, 2, 4 and 6 with a mean of 3.6.  Estimated
mid-latitude A indices were 1, 2, 1, 2, 2, 3 and 7 with a mean of
2.6.
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/EX