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ARRL Propagation Bulletin ARLP013 (2013)

ARLP013 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 13  ARLP013
From Tad Cook, K7RA
Seattle, WA  March 28, 2013
To all radio amateurs 

ARLP013 Propagation de K7RA

This bulletin is issued a day early this week due to the Good Friday

Solar activity was down this week, with the average daily sunspot
number less than half last week's figure, at 49.6. Average daily
solar flux dropped 22 points to 97. Geomagnetic activity was quiet

The predicted solar flux is 95 and 100 on March 28-29, 105 on March
30-31, 110 on April 1-3, 115 on April 4, 120 on April 5-7, 125 on
April 8-10, 120 on April 11-13, 115 on April 14, 110 on April 15,
then it drops below 100 on April 20-24.

The predicted planetary A index is 22, 18 and 8 on March 28-30, 5 on
March 31 through April 22, then 8, 18, 15 and 8 on April 23-26, and
5 through the end of April and into the first week in May.

Lee Gordy, W4KUT of Cartersville, Georgia wrote to say he just
finished reading Carl Luetzelschwab's article "The Sun and the
Ionosphere" in the March 2013 QST for the third time.

Lee wrote, "For me, It's consoling to know that knowledgeable
professionals such as Carl Luetzelschwab are having exciting
difficulties rounding up Ol' Sol's secrets. There's a fine and
mystical line between prophesy and prognosis, and the even bigger
consolation prize I've taken away from Luetzelschwab's informative
writings is a closer understanding of songwriter Joni Mitchell's
wonderful composition, 'Both Sides, Now' -- 'It's cloud illusions I
recall, I really don't know clouds, at all.' I was there for Cycle
19. It was mystical and magical, and I have every hope that I'll
experience a like ionospheric folly before I send my final SK. Who
knows, maybe this cycle will have another peak, and we'll hear
non-stop, worldwide 10 and 6 meter activity. In the meantime, it's
fun to try and outguess Solar Mojo. It's a big part of the
infectious excitement and thrill of amateur radio."

Lee added later, "Regarding the Sun, we can literally see 'both
sides now.' And it just seems like the more we know about it, the
less we really know!"

W4KUT must be referring to the Solar TErrestrial RElations
Observatory project, or STEREO (, which
does allow us to observe both sides of the Sun, with real time
images, too, updated every few minutes.

Bill Tynan, W3XO of Kerrville, Texas (in grid square EM00kd) wrote,
"The CME of March 15 apparently caused a major North/South opening
on 6 meters. Sunday, March 17 at 2122 UTC, I worked HC5VF. He was
S-9 with 50 Watts. I did not hear any Central American stations, so
my conclusion is that it was via F2, not multi-hop Es. I rule out
TEP as HC is above the magnetic equator.

"Then beginning from 2154 to 2256 UT, I worked LUs 7YA, 9EHF, 1DA,
3EX and 7YS. I also heard but did not work, a CX.

"These could have, of course, been TEP, since they are south of the
geomagnetic equator. But, since they followed so closely on the HC,
it makes me wonder."

Bill has an interesting bio and description of his current station
activities on his page, at
You'll need to log in, but the account is free. His email signature
says "700 watts to an 11 element M2 Yagi at 70 feet." I assume that
is for 6 meters.

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 21 through 27 were 60, 54, 56, 45, 56, 41,
and 35, with a mean of 49.6. 10.7 cm flux was 106.1, 100.9, 98.2,
96, 92.6, 92.4, and 93, with a mean of 97. Estimated planetary A
indices were 12, 4, 11, 5, 4, 3, and 14, with a mean of 7.6.
Estimated mid-latitude A indices were 11, 2, 10, 6, 3, 2, and 9,
with a mean of 6.1.


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