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ARRL Propagation Bulletin ARLP002 (2011)

ARLP002 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 2  ARLP002
From Tad Cook, K7RA
Seattle, WA  January 14, 2011
To all radio amateurs 

ARLP002 Propagation de K7RA

Average daily sunspot numbers declined 12 points to 38 during the
past week - when compared to the previous week of December 30
through January 5 - when the average was exactly 50.  Average daily
solar flux declined by nearly six points to 83.8.  The latest
forecast shows solar flux at 80 on January 14-15, 78 on January
16-21, and back to 80 on January 22-25, 82 on January 26, 88 on
January 27-30, and 89 on January 31. The same forecast has planetary
A index for January 14 at 8, January 15 at 7, and January 16-31 at

Geophysical Institute Prague sees unsettled geomagnetic conditions
on January 14-15, quiet to unsettled January 16, unsettled January
17-18, quiet to unsettled January 19, and quiet on January 20.

The STEREO mission's coverage of the entire Sun is nearly complete,
with continuous images showing more than 99.2% of our nearest star.
By Sunday evening in North America, the project will have passed
99.34% coverage.  The black band of unseen area (seen at is now just a tiny sliver, and
magnetically active areas over the entire Sun may now be observed
live from any place with an internet connection at any time of the
day or night.

In last week's Propagation Forecast Bulletin ARLP001 we discussed
W1YO's comments on HF propagation, and this prompted a question from
Howard Lester, N7SO of Schuylerville, New York.  He thought it would
be more instructive if we intended to illustrate seasonal variation
by using the same sunspot number for the April prediction as for the
January prediction.  That is true, but since the prediction engine
is based on a statistical model that employs the predicted smoothed
sunspot number (not the latest actual sunspot number), I thought it
would be interesting to use the official smoothed prediction from
NOAA, to illustrate how conditions might actually play out. Thus we
changed two variables, the date and sunspot number. It is important
to keep in mind that the smoothed sunspot number for January is
predicted as well, because it uses about a year of data to arrive at
the number.  We know what the last six months of data is, but the
component that makes up the next six months is predicted, and
currently unknown.  So in order to know the true smoothed sunspot
number, you need to go back at least six months.

In last week's bulletin we used the table on page 11 of the document
at In that table,
all of the smoothed sunspot numbers from January 2009 through June
2010 are know quantities.  Each month after June 2010 uses a
declining number of months of known data. July 2010 uses 11 months
of known data, and one month (January 2011) of predicted data.
August 2010 uses 10 months of known data, and two months
(January-February 2011) of predicted data, and so on.

How do past predicted smoothed numbers compare with the ones we now
know for sure?  The first six months of 2010 have known smoothed
sunspot numbers of 9, 11, 12, 14, 16 and 16.  If we go back two
months, to the first week in November,
(, the
numbers for the same months track closely (9, 11, 12, 14, 16 and
19).  Of course, going back two months, the only months the smoothed
sunspot number is not known for sure are May and June 2010.

Every time we step back a month, the series diverges a little more
from the actual outcome. At we see
October's projection for those months, and it is 9, 11, 12, 15, 18,
and 21.

Go back to and it is
now 9, 11, 13, 16, 19 and 22 for September.

In August we see 9, 11, 14, 17, 20 and 23 at

In July at we see
variation all the way back to January, at 10, 13, 15, 18, 21 and 24.
You can see now why forecasts for the increase of this solar cycle
keep getting scaled back to track actual outcomes more closely.

W1YO commented this week that Cycle 24 is different. "It's slow to
climb and the effects of high SSNs and solar flux are not long
lasting. I have been through 5 solar cycles and this one is not

Larry Godek, W0OGH of Gilbert, Arizona commented on 6 meters in the
New Year: "January 11 just after midnight GMT, ZL1RS was worked on 6
CW followed by VK3OT then ZL2TPY on SSB followed by VK4MA back on
CW. What a surprise opening that was. Hopefully this is leading us
into a very good January VHF contest weekend coming up soon.
Neither high power nor big antenna systems needed for these QSOs.  I
only have 100 watts and a 5 element Yagi at 40 ft fed with 1/2 inch
hard-line.  Signals were very easily copyable without wearing cans."

Jon Jones, N0JK in Lawrence, Kansas (EM28) reported on January 12,
"Made my first 6 Meter QSO (and first QSO) of the New Year 2011
today with XE2OR/m.

"Rafael was mobile in the rare grid DL97 and worked at 2330 UTC Jan.
9 on 50.125 MHz via E-skip. He was strong with considerable QSB.
Heard him work a few other zeros and N5JEH NM also spotted him. He
was using an IC-706MIIG and a whip antenna.

"Noted 2x Es from Costa Rica to Colorado and earlier in the
afternoon single hop from ZF to W4."

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 an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at  Find more good
information and tutorials on propagation at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for January 6 through 12 were 28, 52, 52, 50, 35,
26, and 23, with a mean of 38. 10.7 cm flux was 86.8, 86.4, 84.8,
82.7, 83.3, 82.6 and 80 with a mean of 83.8. Estimated planetary A
indices were 8, 11, 7, 5, 5, 5 and 6 with a mean of 6.7. Estimated
mid-latitude A indices were 9, 10, 6, 4, 4, 5 and 6 with a mean of


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