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ARRL Propagation Bulletin ARLP051 (2008)

ARLP051 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 51  ARLP051
From Tad Cook, K7RA
Seattle, WA  December 5, 2008
To all radio amateurs 

ARLP051 Propagation de K7RA

This was another quiet week, in which the geomagnetic indicators
hovered around 0, and there were no sunspots.  Look at the A values
for mid-latitude, high latitude, and global at  Sunday through
Tuesday of this week (November 30 through December 2) was another
unusually quiet period, similar to November 11, November 14, and
November 18-24.

The A index -- a linear value -- is calculated from the eight K
index readings for the day, and those are logarithmic values.  It is
somewhat similar to calculating decibels from voltage readings
across a known load, only in reverse.

For an expanded view the web site, shows us these
values for the calendar quarter, back to October 1.  Note that big
changes in the daily A index reflect relatively small changes in the
K index.  The K index is calculated from magnetometer readings.
Middle latitude is from Fredericksburg, Virginia and the high
latitude numbers are from a magnetometer near Fairbanks, Alaska.
The estimated planetary numbers are calculated using data from a
number of magnetometers at various latitudes.

Right now on Friday morning, there are one or two sunspots trying to
break through.  The magnetic activity at our Sun's surface in this
area is not quite at a level to indicate a visible spot.

Compare forecasts at, from USAF/NOAA
from December 3 and December 4.  The December 3 prediction shows
solar flux at 69 for December 5-7, and 70 for December 8-10.
Earlier forecasts had a flux of 70 for only December 8-9, but now on
Thursday's forecast (December 4), we see the flux value of 70
extended to a whole week, December 5-11.  The change to a predicted
solar flux of 70 may coincide with emerging sunspots.

The daily forecast is posted usually after 2100z.  But the December
4 forecast has a second set of values, updated at 1149z on December
5.  It shows a higher A index prediction (changed from 12 to 15) for
December 5.  You can often see a day's forecast a little earlier by
changing the URL on the latest one.  At the end of the URL (web
address) for December 3 are the characters 120345DF.txt, and it
changes to 120445DF.txt for December 4.  Some time prior to 2100z
December 5 you may be able to see the latest forecast by changing
that URL ending to 120545DF.txt, and hitting enter or F5 to refresh,
before the link appears on the main page.

Expect higher geomagnetic activity today (December 5) due to a solar
wind stream.  On December 4 the high latitude A index rose to 20.
As mentioned above, the predicted planetary A index for December 5
is 15.

A note from Mike Reid, WE0H, of Saint Francis, Minnesota mentions
great low-frequency propagation (way below 160 meters) coinciding
with the quiet geomagnetic indicators.

Mike operates on 600 meters (500 KHz, just below the bottom of the
North American AM radio band) with an experimental license,
WD2XSH/16.  He reported on December 2, "I worked a 600m station in
Southern Mississippi at 0700z this morning from Minnesota, with
armchair CW copy on both ends. Only running 90w output here. Very
light fading and zero background noise. 600m has been real good for
a couple weeks or so now."

He continues, "I read this morning on the QRP-L QTH reflector that
the HF bands are completely dead, even 160m. Strange when the HF
bands go dead that 600m opens wide open. 1750 and 2200 meters are
also in excellent shape. 600m and 2200m Part 5 stations have been
crossing into Europe the past few nights with real strong signals."

You can see a picture of the base of his 600-meter antenna at,  Also on that page is a link to Mike's
personal web site, and if you click through, you can eventually get
to, with more info on his LF activity.

Recent Propagation Forecast Bulletin ARLP050 mentioned Tree, N6TR
and his suggestions for a 160-meter antenna.  Regarding the
capacitor, he commented, "You can use a piece of coax as the
capacitor when you determine you have something that will work.  Cut
it long and trim it.  For high power, you might need to treat the
end so it doesn't arc.  I spread out the shield and stick the center
conductor inside a ceramic insulator."

We received quite a bit of mail in the past week that we can't cover
in this bulletin.  We hope to get to this later.  This included
notes from N8II about good conditions on 160 meters with day-to-day
variations, N0JK about 6-meter openings, including thoughts on
meteor showers instead of sporadic-E being the predominate mode at
times, and WB4SLM on 30 meter mid-day openings to Europe.

Don't forget the ARRL 160-meter contest this weekend.  See rules at,  Next
weekend is the ARRL 10-meter contest, with rules at,

And finally, Sid Sosin, W7SID of Bellevue, Washington writes, "I
have figured out the reason why there has been such a paucity of
sunspots for such a long time. It's due to my propensity for
terrible timing:  Besides getting into stocks at their highs, I also
got back into ham radio in 2007 after 25 years off the air, just in
time for the low point of the sunspot cycle, and, at age 84, my
opportunities for propagation maxima are limited."

He continues, "Unfortunately, my punishment for abandoning hamming
for so long is also being inflicted on others."

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 November 27 through December 3 were 0, 0, 0, 0,
0, 0, and 0 with a mean of 0.  10.7 cm flux was 68.2, 67, 68.2,
68.4, 68.1, 68.9, and 69.2 with a mean of 68.3.  Estimated planetary
A indices were 7, 4, 2, 1, 0, 0 and 4 with a mean of 2.6.  Estimated
mid-latitude A indices were 5, 3, 2, 1, 0, 0 and 4 with a mean of


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