Register Account

Login Help

ARRL Propagation Bulletin ARLP013 (2011)

ARLP013 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 13  ARLP013
From Tad Cook, K7RA
Seattle, WA  April 1, 2011
To all radio amateurs 

ARLP013 Propagation de K7RA

The activity we could see recently on our Sun's far side -- thanks
to the STEREO mission ( -- has been
rotating into view, producing some nice sunspot activity and the
resulting improved upper-HF propagation.  Compared to the previous
week (March 17-23), the past week (March 24-30) showed average daily
sunspot numbers up over 61 points to 102.1, and average daily solar
flux up nearly 20 points to 114.7.  Geomagnetic conditions were
quieter as well, and reports from readers show greatly improved
propagation on all the upper-HF bands, 20 through 10 meters.

The table at shows a
new sunspot group on March 23, two more groups appeared March 24,
two more on March 25, and two more on March 27.

The latest prediction from USAF/NOAA, issued Thursday, March 31
differs from the one from the previous day.  The March 30 prediction
was referenced in the ARRL Letter, and the new prediction is less
optimistic in terms of increasing solar activity.

The March 31 projection shows solar flux at 115 on April 1-2, 110 on
April 3-5, 105 on April 6-8, 100 on April 9-10, and for April 11-17
flux values of 95, 95, 90, 88, 88, 90 and 100.  Then they show a
rise to 125 on April 19-27, and 135 on April 28.

The latest planetary A index projection shows an Ap of 8 on April 1,
5 on April 2-7, 8 on April 8, and back to 5 on April 9-17.

Geophysical Institute Prague predicts quiet to unsettled conditions
April 1, quiet April 2-4, quiet to unsettled April 5, and unsettled
April 6-7.

Rob Steenburgh, KA8JBY informs us of the annual Space Weather
Workshop, scheduled April 26-29, 2011 in Boulder, Colorado. Check for details and registration

Rob also reminds us, "There is a nice web application for examining
imagery from the SDO and SOHO spacecraft. It is called 'Helioviewer'
and can be found at There's also an
open-source application folks can load on their computer called
'JHelioviewer' at Users can create
whole-disk animations as well as movie loops zoomed in on active
regions. They can also overlay various images. JHelioviewer and are open-source projects for the visualization of
solar and heliospheric data.  The projects are funded by ESA and

I noticed that seems to work much better than
when it was first announced.  You can zoom in on the latest images,
and also step back in time to see how the Sun has changed over the
previous few hours, days or weeks.

Now that March has ended, we can review some sunspot number averages
over previous months.  The monthly averages for sunspot numbers,
December 2010 through March 2011 were 22, 32.2, 53.5 and 81.1.  This
represents a dramatic increase in solar activity.  We've also been
looking at a 3-month moving average, and the latest is for January 1
through March 31, centered on February. The three month moving
average centered on March 2010 through February 2011 was 22.3, 18.5,
16.4, 20.4, 23.2, 28.9, 33, 35.6, 31, 30.1, 35.3 and 55.7.  So to
review and clarify, 35.3 is the average for all daily sunspot
numbers from December 1 through February 28, and 55.7 is the average
of all sunspot numbers from January 1 through March 31.

Charles Tropp, N2SO of Staten Island, New York is excited about
10-meter propagation.  He writes, "I saw a spot for 5N7M Ivan in
Abuja, Nigeria on Monday 3/29 at 2000 UTC on 28.009 MHz CW so I
checked the frequency and sure enough there he was loud and clear in
Staten Island, NY. He was working US call areas 1,2,3,4 and 5, none
of which I could hear. So I turned on my XIT up about 1.25 and gave
him a call.  He came right back to me about 589. After I logged him
I decided to check my Ham Cap propagation program which I run with
IonoProbe and DX Atlas to see why this QSO was possible with my
backyard vertical and my K3 running 100W. The effective SSN was
about 72 at the time, KP was 1 and yes according to DX Atlas there
was a thin crescent moon shaped propagation path running down Mexico
and Central America, across the South Atlantic and just reaching
Nigeria about 5,230 miles from my QTH.  All of the US was dark which
explains why I couldn't hear any other signals. I just thought I
would share my excitement."

At first I was confused by Charles' description of the propagation
path, because this seemed an unlikely route for his signal to take.
But he is probably talking about areas shown on the map that have
propagation to Nigeria, which could be over a large area.

You can see a nice photo of Charles and his station at Click on the photo to zoom in.

Randy Crews, W7TJ of Spokane, Washington is excited about the
increased solar activity and resulting HF propagation.  He writes,
"This past month has been the most amazing this year for high band
propagation, as I am certain all DXers would agree for Cycle 24.
There have been more days with the solar flux over 100 than below,
in addition reaching a new high. 17 meters sounds like 20, both 17
and 15 are loaded with DX stations from sunrise to well after
sunset. 12 meters has been extremely productive in the past few
days, with EU DX from 1500Z to 2200Z! I have had QSOs with stations
not heard since 2001-02 as folks renew their interest. It really is
great to see the high bands snap back after an incredibly long dry

Mike Shaffer, KA3JAW of Tampa, Florida sent in a link to some video
recordings of broadcast television DX via tropospheric propagation
from Cuba.  You can see it at  This shows several
stations received on Sunday, March 27.

Eric Bowen WK4CW of Winston-Salem, North Carolina sent in this
report: "Just a report from the CQ WPX contest. Between 2200-2300
UTC on 3/27/2011, I was able to work VK4RK and VK4MC along with
several JAs on 10 meter SSB from Winston-Salem, NC. I personally
have not worked any VKs from the East Coast on 10 meters in quite a
long time and all were between 5/7 to 5/9 RST. Rig was FT-920 at 100
watts and Force 12 up 70 feet. Conditions on all bands were good
throughout the contest and the flux at the time was 115 with K and A
indexes both at 1. The SSN was 104."

This report arrived on March 27: "I am Steve Moles N5TEY from
Pawhuska, OK. I have read your propagation column weekly from the
ARRL for years. I have always envied those operators you noted in
your report who had worked the hard to find DX stations on an upper
band. I was fortunate enough to catch one of those openings myself

"I had just came home from church and opened my BandMaster program
and saw that VU2PAI (Ananth in Mangalore, India) was working well
into the US on 12M. I moved late last Fall and only have up a
Cushcraft MA5V using RG-8X feed line at 250 watts from 746 Pro at
this time. The past winter has been tough here and I am just now
preparing to put up my tower for my hybrid cubical quad. The reports
from the cluster reported Ananth as being a true 59 into the
southern US; I thought I would give it a try.

"I turned on the 746 Pro and tuned to 24.965 MHz and VU2PAI was
there at a true 59 at my home in northern OK. I tuned my amplifier
and gave a call up two (24.967 MHz) and Ananth replied to me on the
first call as 59 into southern India at 1613 UTC. I was so shocked I
almost fell out of my chair! One of my daughters was in the room
with me and she asked where the guy was I had just spoken with? She
was amazed at how well he sounded.

"I had read last week about N8II reporting daily openings on 12M
into EU. I was able to experience the 12m opening today myself and
still can hardly believe it."  Check out Steve's site at

Rich Dowty, W7EET of St. Paul, Oregon notes that the DX Sherlock
site ( also shows HF propagation
maps in addition to VHF. You can select HF and any continent to look
at current conditions.

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 March 24 through 30 were 73, 104, 104, 132, 103,
108, and 91, with a mean of 102.1. 10.7 cm flux was 107.6, 112.6,
114.5, 115.6, 118.5, 116.2, and 117.6, with a mean of 114.7.
Estimated planetary A indices were 4, 3, 1, 2, 3, 4, and 5, with a
mean of 3.1. Estimated mid-latitude A indices were 3, 2, 1, 2, 2, 2,
and 4, with a mean of 2.3.


Instragram     Facebook     Twitter     YouTube     LinkedIn