ARRL

ARRL Propagation Bulletin ARLP001 (2011)

SB PROP @ ARL $ARLP001
ARLP001 Propagation de K7RA

ZCZC AP01
QST de W1AW  
Propagation Forecast Bulletin 1  ARLP001
From Tad Cook, K7RA
Seattle, WA  January 7, 2011
To all radio amateurs 

SB PROP ARL ARLP001
ARLP001 Propagation de K7RA

Average daily sunspot numbers were up nearly 24 points this week to
50, and average daily solar flux rose over 9 points to 89.5.  The
lagging 3-month average of daily sunspot numbers was down 3.5 points
from last month's average of the previous three months.  The three
month moving average of daily sunspot numbers, ending on June
through December was 16.2, 20.4, 23.2, 28.9, 33, 35.6 and 32.1.

The latest forecast from NOAA/USAF for the near term has a solar
flux of 88 on January 7, 86 on January 8-9, 84 on January 10, 82 on
January 11, 80 on January 12-15 and 78 on January 16-18, 80 again on
January 19-25, 88 on January 26-30, and 90 on January 31 through
February 2.  Planetary A index is predicted at 7 on January 7, 10 on
January 8-10, 8 on January 11 and 5 on January 12-19.

The geomagnetic prediction from Geophysical Institute Prague is
quiet to unsettled January 7, unsettled January 8-9, quiet to
unsettled January 10, and quiet January 11-13.

Yekta Gursel, KJ6DRO alerted us to an article in the February 2011
issue of "Sky and Telescope" titled "The Perfect Solar Superstorm."
You can read most of it online by going to
http://www.nxtbook.com/nxtbooks/newtrack/st_201102/#/28 and clicking
on "Preview" if you are not a subscriber.  Your local library may
also provide online access to the magazine.  The article begins on
page 28.

David Moore, who is not a radio amateur but has a keen interest in
all things solar, sent a link to a National Science Foundation
article on why the corona of the Sun is millions of degrees hotter
than the surface.  You can read it at
http://www.nsf.gov/news/news_summ.jsp?cntn_id=118338.

Ken Lappe, W1YO of Leesburg, Florida is puzzled by the lack of HF DX
during this time when we have sunspot activity.  He wrote, "The past
few days Jan 3, 4 and 5, the sunspot number has been in the 50 range
and the solar flux in the low 90s with very low A and K indices.
All indications suggest at least fair conditions on the higher
bands.  But this is not the case.  Yes we hear some sporadic-E at
times and some trans-equatorial propagation at times on 12 and 10
meters.  But otherwise the bands are dead, or so it seems. ZL4WW was
weak here in central Florida on 12 meters yesterday around 1900z,
but nothing else was heard.  Even 17 meters has been quiet in the
afternoon and nothing special in the mornings. So, the question is:
If we have sunspots and solar flux and quiet As and Ks where is the
DX?"

It may just be a combination of seasonal Winter conditions and
sunspot activity not high enough to support much long distance
propagation.  A look at a propagation program, such as W6ELprop, is
instructive.

Using a predicted smoothed sunspot number of 39 for January 5 (see
http://www.swpc.noaa.gov/weekly then go to page 11 of the January 4
edition for the source) from Ken's Florida location to New Zealand,
12 meters looks marginal.  17 meters looks good over that path, but
only from 0200-0500z.

Look a few months ahead to April, and with a smoothed sunspot number
of 51, conditions look considerably better.

Now 12 meters opens 1930-0300z, and 17 meters is open during Ken's
local evening until 0530z.

But perhaps Ken is accustomed to better HF openings at this time of
year with this level of solar activity.  In that case, I don't know.

Walt Knodle of Bend, Oregon wrote on January 2, "I had an
interesting experience on 40 meters this morning, interesting
because of the timing relative to reading an article by K9LA on skew
paths in the January 2011 World Radio Online.

"That article was directed toward 160 meter propagation, but seemed
appropriate for conditions on 40 meters today. While listening for
VU2GSM I noticed his signal was stronger along the long path than
the short path. However, the LP was almost entirely in daylight so
something else was at play. In swinging the beam toward the LP I
could hear Kanti's signal pass through a very definite peak between
the SP and LP headings. The best heading was directly SW of my QTH
and along the grey line. Assuming a refraction point near the
equator, this would follow Carl's example from the WRO article and
implicate the equatorial ionization anomaly. One side benefit of the
skew path was that it placed the Chinese OTH radar at 90 degrees to
my beam heading."

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://arrl.org/propagation-of-rf-signals. For an explanation of the
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation.  Find more good
information and tutorials on propagation at
http://mysite.ncnetwork.net/k9la/index.html.

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

Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins.

Sunspot numbers for December 30 through January 5 were 24, 23, 65,
38, 51, 54, and 50, with a mean of 43.6. 10.7 cm flux was 82.9,
90.9, 91, 91.1, 92.1, 90.6 and 87.7 with a mean of 89.5. Estimated
planetary A indices were 5, 4, 3, 3, 4, 4 and 2 with a mean of 3.6.
Estimated mid-latitude A indices were 4, 2, 2, 3, 3, 3 and 2 with a
mean of 2.7.
NNNN
/EX