ARRL

ARRL Propagation Bulletin ARLP017 (2009)

SB PROP @ ARL $ARLP017
ARLP017 Propagation de K7RA

ZCZC AP17
QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 24, 2009
To all radio amateurs 

SB PROP ARL ARLP017
ARLP017 Propagation de K7RA

Teased again, on Wednesday, April 22 we saw sunspot 1015 fade away,
just as it was about to slip over our Sun's western limb.  It
emerged only briefly, late on April 21, and by Thursday it had
disappeared.

10.7 cm solar flux (2.8 GHz radio energy, measured in Penticton,
British Columbia with a parabolic antenna that tracks the Sun) rose
slightly with the sunspot appearance, to 71 and 71.1.  Average solar
flux for the week increased slightly over the previous week, from
69.3 to 70.2.  Both planetary and mid-latitude average A index
declined, from 6.6 to 5.1 and 4.6 to 3.9, respectively.

Sunspots have become so rare that many of us were happy to see
anything at all, and of course a low geomagnetic index is welcome.
One thing about this extended solar minimum: With solar wind
declining and not much to upset our earth's magnetosphere, it is
great for 160 meters.

Calvin Branch, KA1WOR of Hudson, Florida sent a link to an
interesting BBC item about the extended solar minimum.  You can read
it at, http://news.bbc.co.uk/2/hi/science/nature/8008473.stm.  Some
interesting observations in the article include the assertion that
the twentieth century saw high solar activity, and perhaps that is
now quieting down.  Many of us were hoping that the activity fifty
years ago during Cycle 19 was normal, and had hoped that it might
return, but that doesn't seem to be the case.  Too bad, because most
of us get to experience only a few solar cycles.  I was licensed as
a Novice when I was a pre-teen, so I've seen four complete cycles,
and I will probably see five.  But six, or seven?  One can hope.

The BBC seems to do a good job of science reporting, but I'm still
seeing lots of confusion about what the solar cycle is actually
doing.  Tonight I read a blog post making fun of climatologists
which claimed the current solar minimum has been ongoing for nine
years now.  Of course, this is nonsense.  The average daily sunspot
number for each year since 1999 is:

1999 146.3
2000 173 
2001 170.3 
2002 176.7 
2003 109.2 
2004 68.6 
2005 48.9 
2006 26.1 
2007 12.8 
2008 4.7

Those numbers were derived by adding up each year's daily sunspot
data presented in this bulletin, then diving by 365, or 366 in the
case of 2000, 2004 and 2008.

I queried the blogger for more info on his data, but haven't seen
anything yet.

We are beginning to receive reports for the Spring sporadic-E
season.

Mike Schaffer, KA3JAW in grid square EL87 (Tampa, Florida area)
looks for Central American and Caribbean television signals, and on
April 18 sent his first sporadic-E observation since February 22,
when he last received a Guatemala station.  At 2113z he copied WKAQ
in San Juan, Puerto Rico, and 2145z he copied WIPM in Mayaguez.

He wrote, "The distance to both stations is 1,232 miles with a
heading of 118 degrees from Tampa, Florida. I noticed on
AccuWeather.com that a satellite that measures water vapor content
had shown dry air over the Bahamas at 2145z. The half-way point was
616 miles, 45 miles east-northeast from Clarence Town, Bahamas, the
same general area where there was dry air overhead. The event lasted
a total of forty-five minutes before the plasma cloud drifted
out-of-range with no further signals being detected."

On April 19 at 1146 and 1200z he picked up an unidentified station
broadcasting music on channel 2, and on channel 3 the Mexican TV
network Televisa.

He also wrote, "I believe that springtime Es has officially arrived.
I say this because this is when Mexican, Central American, and South
American stations are detected during the early morning hours at my
location. During the winter months, it's the reverse, late afternoon
or early evening hours."

Mike continues, "While I was recording various programming, the logo
from El Super Canal, TGV, Guatemala City, Guatemala showed itself
with a white number three at the top/right of the screen multiple
times.  At 1300z (9:00 AM EDT) the last program that was seen before
it vanished was a Spanish religious service."

Vince Varnas, W7FA of Aloha, Oregon reported lots of 10 meter
activity on April 23 from 0100-0330z (April 22 his local time).  At
0108z he worked LU7KAT, he thinks on trans-equatorial propagation
and shortly after worked KH7XS in Hawaii, he believes on sporadic-E.
He also worked New Mexico and Arizona on sporadic-E.  At 0325z he
worked ZL1BYZ, he thinks on F2 propagation.  He was most surprised
by the last contact, 7,000 miles at 8:25 PM his local time.

Charles Preston, KL7OA of Anchorage, Alaska sent along information
on WSPRnet, the "Weak Signal Propagation Reporter Network."  They
have a web site at http://wsprnet.org/drupal/wsprnet/map.  I don't
know the details, but it appears to be an automated network that
tells users what bands are open between a number of locations.  On
their interactive map, you can restrict the display by time or to a
particular band.

Charles also mentioned using the network for comparing antenna
performance.  He has a paper on this at, http://tinyurl.com/cjphes.

Doug Wetzel, K7IP of Everett, Washington sent in a link
(http://www.kg7hq.wetnet.net/node/55) to a page of propagation info
that his friend KG7HQ maintains.  The map shows overhead foF2 MUF
based on real-time data from ionospheric sounders, or ionosondes.
The data originates at http://www.ips.gov.au/, the Australian Space
Weather Agency.

The outlook for the near term is more of the same, quiet conditions.
Geophysical Institute Prague predicts quiet conditions for April
24-30.  USAF and NOAA predict a nice quiet planetary A index of 5
until May 6-9, when the expect to see a planetary A index of 15, 8,
8, and 8.

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://www.arrl.org/tis/info/propagation.html.  For a detailed
explanation of the numbers used in this bulletin, see
http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
propagation bulletins is at http://www.arrl.org/w1aw/prop/.

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

Instructions for starting or ending email distribution of this
bulletin are at http://www.arrl.org/w1aw.html#email.

Sunspot numbers for April 16 through 22 were 0, 0, 0, 0, 0, 0, and
11 with a mean of 1.6.  10.7 cm flux was 69.9, 69.8, 69.9, 70.1,
69.8, 71, and 71.1 with a mean of 70.2.  Estimated planetary A
indices were 6, 5, 8, 4, 4, 5 and 4 with a mean of 5.1.  Estimated
mid-latitude A indices were 3, 4, 8, 4, 3, 3 and 2 with a mean of
3.9.
NNNN
/EX