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ARRL Propagation Bulletin ARLP016 (2013)

ARLP016 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 16  ARLP016
From Tad Cook, K7RA
Seattle, WA  April 19, 2013
To all radio amateurs 

ARLP016 Propagation de K7RA

Solar activity weakened over the current reporting period (April
11-17), and geomagnetic conditions were stable as well.  The
predicted geomagnetic storm did not happen last weekend, with both
the planetary and mid-latitude A index only rising to 10 on Sunday
April 14 in response to a glancing blow from a CME.

Average daily sunspot numbers declined nearly 25 points to 113.3,
and average daily solar flux was down over 17 points to 121.7.

Predicted flux values for the near term are 95 on April 19, 90 on
April 20-23, 95 on April 24-25, 100 on April 26, 110 on April 27-28,
115 on April 29-30, 120 on May 1-2, 125 on May 3-6, 120 on May 7-8,
and 115 on May 9-12.

Predicted planetary A index is 5 on April 19-22, 12 on April 23-25,
15 on April 26, 5 on April 27 to May 4, 8 on May 5, 5 on May 6-11,
and 8 on May 12.

F.K. Janda, OK1HH of the Czech Propagation Interest Group predicts
the geomagnetic field will be quiet to unsettled April 19, quiet
April 20, mostly quiet April 21, quiet to unsettled April 22, quiet
to active April 23, active to disturbed April 24, quiet to active
April 25, active to disturbed April 26, quiet to unsettled April
27-28, mostly quiet April 29-30, quiet May 1-4, mostly quiet May 5,
quiet May 6-7, mostly quiet May 8, quiet May 9, mostly quiet May 10,
quiet to unsettled May 11-12, and mostly quiet May 13.

Carl Luetzelschwab, K9LA maintains a great website devoted to
propagation information, but it moved recently to a new domain.

Paul Drahn, KD7HB of Crooked River Ranch in Central Oregon wrote: "I
must take exception to your comment about 'great news for HF
propagation.'  It's very difficult for local evening nets on 75
meters. I am active on the Oregon Emergency Net on 3980 from 6pm to
7pm. Just prior to our net, the Tennessee phone net operates on the
same frequency. Afterward, several Tennessee hams use the frequency
as a local rag chew net. At times, like the last two evenings, they
are stronger in Oregon than many of the local check-in stations.
Last night there were at least three conversations going on from
Tennessee, all on 3980. They could not hear each other, and could
not hear the OEN.

"We expect this interference in the Winter, but only is a problem at
other times when the propagation allows it. Fortunately the folks in
Tennessee go to bed early!"

As we move later in the Spring and toward Summer, the signals should
be weaker around net time. It might help if the folks in Tennessee
used NVIS type antennas for local coverage, as they don't have a low
angle of radiation. There are several pages that describe the NVIS,
or Near Vertical Incident Skywave antenna, such as or or

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 More good
information and tutorials on propagation are 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 April 11 through 17 were 121, 128, 148, 111, 99,
97, and 89, with a mean of 113.3. 10.7 cm flux was 137.1, 137.9,
125.1, 116.8, 113.3, 113.3, and 108.1, with a mean of 121.7.
Estimated planetary A indices were 5, 5, 6, 10, 5, 3, and 3, with a
mean of 5.3. Estimated mid-latitude A indices were 4, 4, 6, 10, 6,
2, and 2, with a mean of 4.9.


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