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ARRL Propagation Bulletin ARLP001 (2008)

ARLP001 Propagation de K7RA - Correction

QST de W1AW  
Propagation Forecast Bulletin 1  ARLP001
From Tad Cook, K7RA
Seattle, WA  January 4, 2008
To all radio amateurs 

ARLP001 Propagation de K7RA - Correction

It's a new year, and now time to review 2007 sunspot cycle
progression.  In 2006 there was a consensus that solar minimum would
occur in early 2007, but we actually may not be there still.  The
latest projection in the Weekly Preliminary Report and forecast (see and page 8 in the January 2 issue)
shows the bottom of the cycle between December 2007 and April 2008.
Note the two predictions for the next cycle, a high estimate and a
low estimate, reflecting the split consensus for the Cycle 24

Also note the monthly (even though the URL says weekly) forecast
issued on January 2 at, shows a cycle minimum
for February 2008.

Exactly one year ago in Propagation Forecast Bulletin ARLP001 we
wrote that 2007 would be "the year we'll likely see the end of
sunspot Cycle 23, the beginning of Cycle 24, and the minima between
cycles."  Now a year later we might say the same about 2008.

The yearly average of the daily sunspot numbers for 1999-2007 were
136.3, 173, 170.3, 176.6, 109.2, 68.6, 48.9, 26.1 and 12.8. Average
daily solar flux for the same years was 153.7, 179.6, 181.6, 179.5,
129.2, 106.6, 91.9, 79.9 and 73.1.

Compare 2006-2007 above with the last solar minimum, when in
1995-1997 the yearly averages of sunspot numbers were 28.7, 13.2 and

In February 2007 we began calculating and tracking a 3-month moving
average of daily sunspot numbers.  This was done to try to spot
trends.  A three month period seemed like it might give us some
smoothing of the often volatile daily numbers, but much shorter than
the 12-month smoothed values.

Apr 06 38.5
May 06 39.7
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

Why is November the last month on our list?  Because it is the
center month for the latest 3-month average, which is for October
through December.  If we were instead calculating a 12-month moving
average, at the end of December the latest number would center on
June 2007.

Last week's bulletin reported 10-meter openings, and said that
E-skip was unexpected at this time of year.  Actually there is a
small peak in sporadic-E propagation centered around Winter
Solstice, about 1/5 to 1/8 the intensity of the Summer sporadic-E
season.  The propagation reported by K7HP occurred just hours from
the precise time of solstice.

One of several who spoke up concerning Winter E season in response
to last week's bulletin was Bill Van Alstyne, W5WVO of Rio Rancho,
New Mexico.  Bill said that Winter E-skip is, "more likely to happen
during the evening hours than during the morning, while Summer Es
occurs during morning and evening about equally -- though that's
just percentages and probability. We just had a nice morning Es
opening a couple days ago on 6 meters."

Another Winter solstice 10-meter report came from Joaquin Montoya,
EA2CCG, who reported working a number of Italian and French stations
with his "fishing rod antenna."  If you can read Spanish, or even
want to try out one of those online language translators, check out
his blog at,

A December 30 10-meter E-skip report came from Oleh Kernytskyy,
KD7WPJ of Saint George, Utah.  In the morning he heard a strong
beacon signal from K5AB, then he called CQ on CW with no response.
He moved to phone and had many contacts, including the states of UT,
NM, TX, OK, AR and FL.

See for an interesting
treatment of E-layer propagation.

So what's up for the next week?  Sunspot 978 reappeared, and the
daily sunspot numbers for Tuesday, Wednesday and Thursday were 11,
13 and 13, while solar flux was 79.4, 79.6 and 79.3.  The US Air
Force and NOAA Space Weather Prediction Center forecast rising solar
flux values of 80 for January 4-5, 85 for January 6-8, and 90 for
January 9-11.  This is a slight move downward and outward.  As
recently as two days ago, they were predicting flux of 95 for
January 7-9.

They also forecast planetary A index for January 4-10 of 10, 10, 5,
8, 8, 5 and 5. The next unsettled to active period is predicted for
January 13-14 with a planetary A index of 15. After 2100z today look
for an updated forecast of solar flux and A index at  Please note
this is a hacked URL, that only works after 2100z Friday.  It is
updated daily, so for Saturday, January 5 after 2100z, the URL would
end /010545DF.txt. This hack was explained back in October 2007, in
ARLP044, found at

Geophysical Institute Prague predicts quiet to unsettled conditions
January 4-5, unsettled January 6-7, quiet to unsettled again on
January 8, and quiet conditions January 9-10.

The last few days have had very quiet with stable geomagnetic
conditions.  This should correlate with lower absorption of HF
signals.  You can see interesting very quiet numbers at,  Note the planetary
A index for January 2-3 was 1 for both days, but all of the K index
readings for those days were 0.  Contrast that with the high
latitude college (Fairbanks, Alaska) readings for January 2.  There
is just one K index reading of 1, but the A index reading for that
day is 0.

KN4LF writes that he has decided to make his daily propagation
forecasts free again, and you can see them at,  He also has a sign-up option
there for email bulletins.

Last, today I am buying a used car from a private party found via an
online ad.  The seller turned out to be the grand-daughter of the
original holder of VE7BR, A.J. Spilsbury, a remarkable Canadian
radio pioneer who manufactured HF gear for marine and wilderness
communications in British Columbia.  Spilsbury was also an
accomplished painter, photographer, author of several books, and he
founded a regional airline.  He became a Silent Key in 2003 at age
97.  I found information on him by googling his last name alone, or
combined with other search terms such as "radio."

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,

Sunspot numbers for December 27 through January 2 were 0, 0, 0, 0,
0, 11 and 13 with a mean of 3.4.  10.7 cm flux was 72.1, 71.8, 72.7,
75, 76.7, 79.4, and 79.6 with a mean of 75.3.  Estimated planetary A
indices were 4, 2, 2, 2, 2, 3 and 1 with a mean of 2.3.  Estimated
mid-latitude A indices were 4, 2, 2, 3, 2, 2 and 1, with a mean of


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