ARRL Propagation Bulletin ARLP017 (2013)

ARLP017 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 26, 2013
To all radio amateurs 

ARLP017 Propagation de K7RA

Solar activity quieted this week. The average daily sunspot number
declined nearly 23 points to 90.6. Average daily solar flux values
were down nearly 13 points to 109.1. The most active day was April
24, with a planetary A index of 19 and mid-latitude A index of 15.
But that is still quite moderate activity.  The average daily
mid-latitude A index was the same this week as last, 4.9.

The predicted solar flux is 120 on April 26-29, 125 on April 30
through May 1, 130 on May 2-3, 125 on May 4-5, 120 on May 6, 115 on
May 7-8, 120 on May 9-11, 115 on May 12-13, 110 on May 14-15, 105 on
May 16-18, 110 on May 19 and 120 on May 20.

The predicted planetary A index is 12 on April 26, 5 on April 27
through May 4, 8 on May 5, 5 on May 6-18, and 8, 12, 12, 15, 12 and
5 on May 19-24.

F.K. Janda, OK1HH predicts the geomagnetic field will be quiet to
active April 26, quiet to unsettled April 27 to May 10, quiet to
active May 11-12, and quiet to unsettled May 13-19.

The Australian government's Ionospheric Prediction Service issued a
geomagnetic disturbance warning at 0503 UTC on April 26. Increased
geomagnetic activity is expected due to a high speed solar wind
stream from a low-latitude coronal hole. Minor storm levels are
possible. Active to minor storm levels are expected April 26, and
unsettled to active levels are expected April 26-27.

See You can go to to subscribe to their alert

Bob Logan, NZ5A lives in Manor, a tiny town in central Texas. On
Sunday, April 14 at 2032 UTC he was surprised to work HC2UA
(Ecuador) on 6 meter CW. Bob ran 4 watts with a Flex 1500.  The
antenna was unusual, an 80 meter inverted vee with the center at 35
feet, fed with ladder line and an HF antenna tuner, which Bob says
"is not designed to tune 6 meters, but it does!" He also worked them
at 2043 UTC on SSB, although they were not able to copy his report.
"Quite exciting for me!" says Bob.

Jeff Hartley, N8II of Shepherdstown, West Virginia wrote on April
19: "10 and 12 meters have been quite poor with the recent solar
activity decline, but 15 and lower continue to delight with 20 open
to western EU and the middle East thru most if not all of their
night. There were tremendous signals on 10 meters from south central
and SE EU during the recent flux in 140s, the best days being April
10th and 11th.

"The highlight of propagation was working VK9CZ (Cocos-Keeling) on
10 CW easily around 1400 UTC and hearing JAs around 2230-2330 UTC on
10 one night with one JA QSO. I had a run of JAs on 12 meter SSB
with the loudest over S9."

Scott Bidstrup, TI3/W7RI sent an article about a study with a pair
of sounding rockets to see if turbulence in the E-region of the
ionosphere at sunset could serve as a warning of disturbance in the
F-layer an 1-2 hours later.  Read it at

NASA has a new video of the Sun showing three years of continuous
images. In that time, if the Sun rotates relative to Earth about
every 27.5 days, then this video should show 398 rotations of the
Sun, in less than 4 minutes.  Watch it at,

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

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bulletins are at

Sunspot numbers for April 18 through 24 were 86, 101, 101, 76, 83,
95, and 92, with a mean of 90.6. 10.7 cm flux was 105, 99.4, 104.9,
109.3, 112.9, 117.5, and 114.7, with a mean of 109.1. Estimated
planetary A indices were 3, 2, 4, 3, 4, 7, and 19, with a mean of 6.
Estimated mid-latitude A indices were 2, 1, 2, 3, 5, 6, and 15, with
a mean of 4.9.