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ARRL Propagation Bulletin ARLP016 (2006)

ARLP016 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 16  ARLP016
From Tad Cook, K7RA
Seattle, WA  April 21, 2006
To all radio amateurs 

ARLP016 Propagation de K7RA

Geomagnetic activity was higher over the past week, with the average
daily planetary A index rising over six points to 18.  The most
active days were Friday and Saturday, April 14 and 15, when the
planetary A index was 58 and 29.  All this and auroras too were
caused by a stiff solar wind meeting an interplanetary magnetic
field pointing south, making Earth vulnerable.

Otherwise, geomagnetic activity has been low and should stay that
way.  Sunspot numbers and solar flux should rise gradually, reaching
a peak around April 29 through May 3.

Predicted planetary A index for April 21-25 is 8, 8, 10, 8 and 8.
Geophysical Institute Prague predicts quiet to unsettled conditions
for April 21, unsettled conditions April 22-23, quiet to unsettled
April 24-25, and quiet conditions April 26-27.

For this week's report we were missing solar flux data for April 18.
For some reason the report from observatory in Penticton, British
Columbia did not show any noon data on that date.  See

So we averaged the morning (75.4 at 1700z) and afternoon (75.8 at
2300z) readings with the solar flux from NOAA (74) and came up with
75.1.  At Penticton they measure the 10.7 cm solar flux three times
per day, at 1700z, 2000z and 2300z, but it is only the local noon
reading at 2000z that gets reported as the official flux value for
the day.

Several hams reported interesting or unusual propagation recently.
Grant Hollands, VA7GO of Victoria, British Columbia (on Vancouver
Island) reports that last week (April 12) he was sitting on a bench
on Mt. Tolmie (a park in Victoria) running 2.5 watts into a home
made whip.  After sunset around 0300z he heard a strong signal from
W5QG in Texas on 14.21 MHz and gave him a call.  W5QG gave him a 4x6
signal report.  Then he worked ZK1JD at South Solomon Islands, who
gave him a 3x4 report.  Well, maybe none of that is unusual, but it
is nice to know that running a couple of watts from a park bench
using a whip antenna does allow you to make some contacts.  Grant
said that in February 2005 on 6 meter SSB using 2.5 watts and a
handheld he worked Hay River in the Northwest Territories.  Hay
River is about 60.8 degrees north latitude, 115.8 degrees west
longitude.  He notes that so far this year he hasn't worked any 6
meter QRP DX.

Mike Giddings, G3XLB writes that even when the geomagnetic
conditions were acting up recently, he still made contacts over long
distances.  Mike is in London, and says that he couldn't hear any
North American stations on April 14, but worked Asia, Malaysia,
Cambodia and Indonesia with reports over S9.  Yet recently when the
K index was low, conditions seemed worse.

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 found at,

Sunspot numbers for April 13 through 19 were 69, 62, 45, 45, 48, 46
and 38 with a mean of 50.4. 10.7 cm flux was 80, 78.9, 78.4, 76.5,
77.9, 75.1, and 75.8, with a mean of 77.5. Estimated planetary A
indices were 13, 58, 29, 10, 6, 6 and 4 with a mean of 18. Estimated
mid-latitude A indices were 9, 32, 18, 8, 4, 5 and 2, with a mean of


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