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ARRL Propagation Bulletin ARLP017 (2006)

ARLP017 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 17  ARLP017
From Tad Cook, K7RA
Seattle, WA  April 28, 2006
To all radio amateurs 

ARLP017 Propagation de K7RA

Geomagnetic conditions were quiet this week in most places, but on
April 22 there was a geomagnetic storm at high latitudes caused by
solar wind and a south-pointing IMF. The college A index in
Fairbanks Alaska reached 38, and the K index was 7 at its highest.
The mid-latitude A index for the day was only 10, just slightly

On April 27 there was a strong but brief solar flare from sunspot
875, but this is not expected to cause major geomagnetic activity.
At the time of the flare, around 1552z, x-rays caused a short radio
blackout of nearly a quarter hour.

Sunspot numbers and solar flux have been rising, and solar flux is
expected to remain around 100 over the next week. Geomagnetic
conditions may become active again around May 2 and May 6, with a
big increase in activity around May 10-13 expected because of
similar activity during the previous solar rotation.

Steve Lybarger, NU7T of Reno, Nevada wrote asking about sunspot
polarity, and where he could get information on the actual polarity
of currently visible spots. I told him I didn't know, but did find
this interesting page from "Mr. Sunspot's Answer Book" at the
National Solar Observatory web site,

Ron Wright, ZL1AMO (and others, including AE6RR) wrote in to say
that ZK1JD, mentioned in last week's bulletin as worked by VA7GO, is
not actually in the South Solomon Islands, an area of great civil
unrest currently. Jim Ditchburn, ZK1JD is actually in Rarotonga in
the South Cook Islands. Craig Bradley, AE6RR worked ZK1JD a few days
ago on 20 meters, and when told about his call appearing in the
bulletin, Jim commented that he "would not want to be in the Solomon
Islands at this time!"

Greg Andracke, W2BEE of Pine Plains, New York tells about some
unexpected propagation from a couple of weeks back. On Saturday,
April 15 at 1123z he heard VQ9LA of Chagos calling CQ on 30 meters
with no takers. Greg scrambled to tune his 20-meter vertical to 30
meters, and reached VQ9LA, neither station having strong signals.
Afterward Greg could hear no other stations called the DX station.
Odd propagation for that time, but it would have been normal about
10-14 hours later.

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 and an explanation
of the numbers used in this bulletin, see the ARRL Technical
Information Service propagation page at, An archive of past
propagation bulletins is at

Sunspot numbers for April 20 through 26 were 30, 14, 15, 24, 38, 33
and 60 with a mean of 30.6. 10.7 cm flux was 78.7, 76.4, 82.4, 86.7,
92.8, 95.1, and 100, with a mean of 87.4. Estimated planetary A
indices were 5, 8, 18, 8, 7, 5 and 5 with a mean of 8. Estimated
mid-latitude A indices were 3, 6, 10, 8, 4, 1 and 2, with a mean of


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