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ARRL Propagation Bulletin ARLP019 (2012)

ARLP019 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, K7RA
Seattle, WA  May 11, 2012
To all radio amateurs 

ARLP019 Propagation de K7RA

Average daily solar flux for the past week rose slightly, 116.2 to
119, but average daily sunspot numbers declined more than 14 points
(about 13%) to 92.6.

Predicted solar flux for the near term is quite a bit higher than
the average for the past week. Solar flux on May 11-18 is 130, and
then it drops sharply to 110 on May 19-22, 115 on May 23-25, 110 on
May 26, 105 on May 27-31, 110 on June 1-2, and 115 on June 3-10.

Predicted planetary A index is 12 on May 11-12, 10 on May 13, 5 on
May 14-18, 8 and 10 on May 19-20, 15 on May 21-23, 8 on May 24, 5 on
May 25 through June 4, 12 on June 5-6, 18, 10 and 5 on June 7-9, 8
on June 10-11, then 5, 8, 5, 8 and 10 on June 12-16, and 15 on June

Right now sunspot group 1476 has been producing a lot of activity,
and could give us an X-Class solar flare. It is currently pointed
straight at Earth, at the center of the visible solar disk.  This
sunspot is the subject of news reports lately, including,

If you like your solar news with dramatic music, don't miss these

This week you can compare the tables in the Preliminary Report and
Forecast at and the
earlier version at
and see the slight decline in estimated and predicted smoothed
sunspot numbers for October 2011 through October 2012.  These
smoothed numbers are averaged over a whole year, so a current number
would be an average made up of half predicted numbers and half
actual sunspot numbers for the past half-year.

David Gerns, K1LD of Plaistow, New Hampshire sent a link to a
remarkable article on the "Carrington Event of 1859, the Great
Auroral Storm."

Read it at,
and note the exchange between the two telegraphers in which they
observed better performance of the telegraph system by disconnecting
their batteries, and just using the induced currents from the

I also was not aware that recordings were made from magnetometers
150 years ago, such as the one shown in the article.  Also note that
at the end of the piece is a link
to a collection of eyewitness reports of this event.

Josep, EA3AKY of Catalunya Spain wrote on May 4: "I'm a 6 meter DXer
and appreciate very much your information. This band is not easy and
sometimes surprises me. In spite of this low Sun activity, today I
worked OA4TT at 1810 UTC at 10029 Km. Signal on CW was 519-529 with
some flutter and quick QSB. Jack has worked several other EAs and
CTs. After Jack, I worked UR7FM/MM in field IG28. Propagation to
Jack was sporadic-E (EA8 and CS3 were in at same time) linking to F2
/TEP layer."

Fred Honnold, KH7Y of Ocean View, Hawaii wrote: "We still are having
openings just about every evening from 0500 to 0800 UTC to
DU7/PA0HIP with very good signals most of the time peaking S9+10.  I
was lucky and worked 9M0L on April 21, 2012. They were into KH6 for
over 2 hours with their beacon, thanks to Dave N2NL was able to
alert them on 10 meters to man their six meter station and look
towards KH6.  I am not sure if any other KH6 stations worked them.
Also on April 21 worked YN2N, 9M6XRO, DU7/PA0HIP all with big
signals 30+ over S9.

"Last night I worked KG6DX, BV2DQ, was copied by Han, JE1BMJ 519,
and I was hearing KH0/W3STX but could not get their attention.  So
the six meter band is alive and well out here."

Tom McGuire, W0VPI of Davenport, Iowa asked about a website that
would show him real time MUF, or Maximum Usable Frequency. The
problem is there is no single MUF value, as it varies according to
the path, or the location of the two endpoints.

I mentioned that he could estimate MUF using W6ELprop, available at  MUF programs are written to use the
predicted smoothed sunspot number for the month.  Apparently they
aren't any more accurate if you use the current daily sunspot
number, but one compromise might be to average the sunspot number
over the past few days.

For the day that I was using in my example, the average sunspot
number would be 99. I calculated that at 2200 UTC on that day the
MUF would be about 21.7 MHz between my place in Seattle and W0VPI in

I continued, "Interesting that throughout the day and night, the MUF
doesn't vary much.  The lowest it goes at 3:00 AM my time (1000 UTC)
is 15.1 MHz, so 20 meters is always open between us. 17 meters looks
like the best band between us at the moment.

"You can see how location dependent MUF is by entering the default
location for Brazil, PY. The MUF is above 28 MHz from your place
from 1530-2200 UTC, all day long."

To look at real time conditions, you could use  Note that you can customize
it by band.

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 May 3 through 9 were 107, 101, 88, 104, 79, 90,
and 79, with a mean of 92.6. 10.7 cm flux was 114, 114, 116, 117.3,
121.7, 122.8 and 127.3, with a mean of 119. Estimated planetary A
indices were 8, 4, 4, 5, 4, 9, and 24, with a mean of 8.3. Estimated
mid-latitude A indices were 9, 4, 4, 5, 4, 8, and 19, with a mean of


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