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ARRL Propagation Bulletin ARLP009 (2011)

ARLP009 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 9  ARLP009
From Tad Cook, K7RA
Seattle, WA  March 4, 2011
To all radio amateurs 

ARLP009 Propagation de K7RA

Solar activity is rising again, but average sunspot numbers and
solar flux are down compared with last week. This week the average
daily sunspot number declined over 14 points to 50.9, and average
daily solar flux was off 7 points to 96.8. Average daily planetary A
index rose from 6.1 to 9, and the average mid-latitude A index was
about the same, declining from 5.4 to 5.1.

You can see daily sunspot and solar flux numbers, updated after
0230z at
Geomagnetic indices are updated 8 times per day at Our weekly data
reports at the bottom of this bulletin run Thursday through
Wednesday, so at the above links you can see that yesterday
(Thursday, March 3) the planetary A index dropped from 17 to 12 and
the daily sunspot number went from 83 to 71.

The most active day for geomagnetic indexes was March 1, with a
planetary A index of 31. The planetary K index rose as high as 6 on
that day. Polar propagation paths were disturbed, with the College A
index (measured near Fairbanks, Alaska) for March 1-3 at 53, 43 and

NOAA and USAF predict solar flux of 120 on March 4-11, 110 on March
12-15, 105 on March 16-17, and 100 on March 18-21. Planetary A index
is forecast at 12 on March 4-5, and 5 on March 6-13, 7 on March
14-15, and 5 on March 16-21.

You can get the daily NOAA/USAF prediction for solar flux and
planetary A index at The forecast
is usually updated by 2130z daily.

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

It looks like good conditions for the ARRL International SSB DX
Contest this weekend, or at least much more interesting than the
past few years, due to increased solar activity. Along with this
comes the greater risk of geomagnetic disruption from solar flares,
coronal mass ejections and gusts of solar wind. I received some
comments from 80 and 160 meter DXers during the recent minimum
noting that they loved the absence of solar activity, because
everything was so quiet and stable.

For this year's DX contest we are seeing sunspot numbers in the
range of 20-100, but for the first ten days of March 2010 the
average sunspot number was 20.1, for 2009 it was 2.4, 2008 it was
3.7, 2007 it was 14.9 and 2006 it was 14.1.

The monthly average of sunspot numbers for December 2010 through
February 2011 was 22, 32.2 and 53.5, reflecting the rise in solar
activity. The three-month moving average of sunspot numbers centered
on January (an average of all daily sunspot numbers for December
2010 through February 2011) was 35.3. The three-month moving average
of daily sunspot numbers centered on each month of 2010 was 22.4,
25.7, 22.3, 18.5, 16.4, 20.4, 23.2, 28.9, 33, 35.6, 31, and 30.1.
The average centered on January 2011 is back up to the level it was
in November 2010, 35.6.

Big news this week was about the solar model explaining the deep
solar minimum we've just experienced. Thanks to all the readers who
sent emails about this. See the story at,,

Johnathon Ballard, KI4UKF lives in Stokes County, North Carolina,
less than 10 miles south of the Virginia state line. On Wednesday,
March 2 at 1655z (just before noon local time) he heard Claudio
Costa, LW2ECC (Argentina) calling CQ on 2 meter FM, on 144.48 MHz.
KI4UKF was using a Moxon wire antenna tacked to a wall, and said the
signal was steady for several minutes at about S6, then faded away.
He emailed Claudio, who confirmed the transmission. Claudio was
using three 5/8 wave verticals and 160 watts.

John Shew, N4QQ of Silver Spring, Maryland was in Curacao for the
ARRL DX CW Contest and operated at PJ2T. He had some interesting
observations about trans-equatorial propagation on 6 meters into
South America.

He wrote, "Thursday evening around 8 PM (0000z February 19) W9VA and
I decided to check 6 meters looking south for TE propagation. The
equipment at PJ2T is a Yaesu FT2000 and a M2 5-element at 70 feet
with a clear shot over water to South America. Much to our joy the
band was full of LU beacons at S9 strength. At 0015z we tuned up to
50.110 MHz and I called CQ using the call PJ2/N4QQ. Over the next 15
minutes I worked 16 stations in 14 grid squares. Signal strengths
were S7-S9 plus. Stations included:

PY4LH GG68   PY4OY GG78   LU4FW FF97   PP5XX GG53   LU2NI FG72

"We kinda worked the band empty after 15 minutes but it was still
open, but there were no more stations calling us so we moved back
over to the HF bands.

"It was a great thrill for me to experience TE propagation for the
first time after reading about it many times in the ARRL VHF column
over the last 50 years. Signals sounded slightly hollow, but were
quite strong with no obvious QSB. The band appeared to open to all
areas at once, with no obvious flashlight effect, experienced during
E-skip. I plotted the grid squares I worked and they fall in a band
about 600 miles deep between 2700 and 3300 miles to the south,
crossing the entire South American continent. The plotted skip zone
appears to slightly skew from southwest to northeast, with stations
to the west farther south than those to the east.

"As I have no experience with TE I don't know if this propagation is
common for this time of year or if it occurs throughout the year or
if it is enhanced by recent solar events. (Solar flux peaked
somewhere between 115-125 during our time in PJ2.) With our
attention focused on the DX contest we didn't have a lot of time to
check 6 meters, but the few days we did check it appeared open to
the south from 0000 to at least 0200z.

"It was my impression that TE is a very reliable mode of
communication to the south from the southern Caribbean this time of
year in the early evening. I have been checking 6 meter spots for
the last week and the PYs and LUs have been having a field day
beaming north in the late afternoon and early evening, with numerous
contacts with KP4, TI, FM, YV, P40, etc. PY5XX and others have also
worked EA and CT in Southern Europe and EA8 in Africa. In fact, I
think now I understand one reason why 6 meters is so popular with
the southern PYs and LUs. From PJ2 it appears there are only 5
countries we can work on TE -- PY, LU, CX, ZP, and CE. I worked all
but one in less than 15 minutes. Maybe 4 or 5 more countries can be
worked from PJ2 via TE if one counts islands with DXpeditions like
Juan Fernandez, Trindade, etc. On the other hand PYs and LUs see in
their regular TE skip zone maybe 25 countries with active 6 meter
populations; the countries include the northern coastal South
American countries, much of Central America, the Yucatan, and most
of the Caribbean from Puerto Rico south."

Thanks, John for a fascinating report!

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 February 24 through March 2 were 23, 31, 49, 44,
54, 72, and 83, with a mean of 50.9. 10.7 cm flux was 88.9, 88.2,
90.2, 90.4, 95.8, 110.5 and 113.4 with a mean of 96.8. Estimated
planetary A indices were 3, 3, 4, 2, 3, 31 and 17 with a mean of 9.
Estimated mid-latitude A indices were 0, 1, 2, 1, 2, 18 and 12 with
a mean of 5.1.


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