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ARRL Propagation Bulletin ARLP051 (2010)

ARLP051 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 51  ARLP051
From Tad Cook, K7RA
Seattle, WA  December 23, 2010
To all radio amateurs 

ARLP051 Propagation de K7RA

This bulletin is posting nearly a day early, because ARRL
Headquarters is closed on December 24.  Next week the bulletin will
also be out late Thursday instead of the usual Friday distribution,
as ARRL is closed on December 31.  There is no ARRL Letter until
January 6, 2011.

Sunspots disappeared this week.  Five days with no spots is the
longest since May 9-19, 2010, when we saw 11 days in a row in which
the Sun was spotless.  Since then there has only been the occasional
day or two that was spot-free. April 2010 saw 13 consecutive days
with no spots, followed by one day in which the sunspot number was
12 (indicating the emergence of a sunspot group with two spots),
only to be followed by another spotless day, April 29.

As this bulletin is being written early Thursday, December 23, there
may be a spot emerging right in the center of our Sun, when viewed
from Earth.  It is visible as a white area when viewing the image
from the STEREO mission at, although
this image just shows magnetically active areas in a lighter shade,
which does not always correspond to areas with sunspots.  Viewing
the rest of the image out to the eastern horizon (left side, on
solar images) shows no dramatic activity.  Unfortunately, the Solar
Dynamics Observatory Joint Science Operations Center has experienced
a disk controller failure, and until it can be replaced, the latest
image they have is from December 19.  There is a recent H-Alpha
image at

With no spots for five days, the average daily sunspot number for
December 16-22 dropped nearly 23 points to 4.9.  Average daily solar
flux declined 8 points, or a little over 9%, to 80.1.

The noon reading at the Penticton observatory showed the solar flux
rose today to 80.1, precisely the arithmetic average listed below
for the prior seven days.  Although still pretty weak, solar flux
hasn't been this high since last weekend, on Sunday, December 19.

NOAA/USAF sees a low solar flux of 78 until December 26-27, when
they predict a flux value of 80, then 82 for December 28-29, 84 on
December 30, and 90 on December 31 and January 1.  They also show
low geomagnetic activity with a daily A index of 5, except for
December 25, with an index value of 7.  They show the A index going
back to 5 until the third week in January 2011.

Geophysical Institute Prague always has a more detailed outlook on
geomagnetic activity, and they show quiet conditions for December
24, quiet to unsettled December 25, quiet December 26, quiet to
unsettled December 27, and unsettled December 28-29.

For some, a dead quiet A index with no sunspots might be ideal for
the Winter Solstice, which was on December 21 at 2338z in the
Northern Hemisphere.  Long nights with low seasonal noise from
lightning signal good conditions on 80 and 160 meters, and with
quiet geomagnetic conditions, even better.

Chris Scibelli, NU1O lives in grid square FN32rb in Longmeadow,
Massachusetts. On 10 meters he runs 100 watts into a 3 element beam
at 55 feet.  He sent us a message after reading about the December
14 E-skip opening on 6 meters in the last bulletin.  Chris writes,
"On December 13 after the 10 meter contest ended we had about a 4
1/2 hour E-skip opening to GA, TN, NC, and VA.  Most of the guys
were running ground mounted verticals with 100 watts. I went QRT at
0500z as I put in a full 36 hours in the contest and that was enough
radio for a weekend.  I don't know if there was any relation to what
you wrote about but what was ironic was we did not have decent E
layer openings during the contest. Most of the states I worked at
the normal E layer distance were extremely weak -- about an S1. I
did have an opening to the West Coast on both the 11th and 12th but
signals weren't very strong, either. Toward the end of the contest
on Sunday I had a great opening to LU and PY. Most were 59 to 59

Brett DeWitt, W0BLD lives in Southwest Missouri, near Springfield,
and says that he worked a lot of E-skip on 6 meter SSB to both the
east and west coasts on December 13.  He runs 100 watts to a 3
element Yagi at 25 feet, and you can see a log of his contacts by
querying the DX Sherlock database at He wrote, "The opening lasted
for several hours. I try to log MOST of my VHF QSOs on the site. Worked QSOs from Myrtle Beach SC to Los Angeles CA.
Some contacts I worked a couple different times over several hours
apart.  Florida mainly came in first for a couple hours along with
SC, VA, GA, MS and AL. Then later in the opening NM, AZ, CA started
booming in here with CO in and out. I think I was able to work one
Colorado station. There were also openings several days after the
13th. The band was real good for about a week. I started out in the
afternoon and the band was open till I think 9pm or so if I recall

To see Brett's contacts at
most of the settings can be left at default values, but select 50
MHz, reported from 12 December 2010 to 18 December 2010, containing
the callsign W0BLD, and set the maximum number of returned QSOs to
100 or greater.

Note that in the returned listings, you can click on any of the
callsigns, then click on the maps link to see where their grid
locator is.  Or you can click on the grid locator, and see all of
the stations reporting from that same locator.

Merry Christmas from K7RA.

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 December 16 through 22 were 23, 11, 0, 0, 0, 0,
and 0, with a mean of 4.9. 10.7 cm flux was 84.1, 81.6, 80.5, 80.9,
77.9, 77.9 and 77.7 with a mean of 80.1. Estimated planetary A
indices were 5, 3, 2, 1, 8, 1 and 0 with a mean of 2.9. Estimated
mid-latitude A indices were 4, 2, 2, 2, 6, 1 and 1 with a mean of


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