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ARRL Propagation Bulletin ARLP012 (2005)

ARLP012 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 12  ARLP012
From Tad Cook, K7RA
Seattle, WA  March 25, 2005
To all radio amateurs 

ARLP012 Propagation de K7RA

Seasonally this is a great time for HF propagation, as the Northern
Hemisphere passed into spring last Sunday.  But sunspot activity is
low as we slip toward the bottom of the cycle, still estimated at
nearly two years away.

The weekly average of the daily sunspot number slipped over 16
points from last week to 44.3.  The daily average of solar flux was
down over 12 points to 92.1.  Geomagnetic A and K indexes showed
stable conditions, but slightly unsettled on March 19.  There were
many periods with the K index at zero or one, even at high
latitudes.  For the entire day on March 22, the College K index from
Fairbanks, Alaska was zero, which produced an A index for that day
of zero.  This was even slightly lower than the planetary or
mid-latitude values for that day.

The forecast for this week shows more of the same, with solar flux
slipping below 90.  A solar wind stream may cause some unsettled to
active conditions.  The U.S. Air Force shows unsettled to active
conditions with a planetary A index around 15 for March 27-29.  RWC
Prague shows unsettled to active conditions for March 26 and 27,
with unsettled conditions for March 25, 28 and 29.

Noel Petit, WB0VGI, sent a link to a magnetometer in Minnesota which
is on a rural farm north of Minneapolis.  The approximate location
is northwest of Cambridge, Minnesota at 45.616 degrees N, 93.312
degrees W.  You can observe the output in terms of K index from a
server at Augsburg College at  This is similar
to a K index from NOAA generated by 9 magnetometers in North America
The Cambridge K index gives a nice localized indication of real time 
geomagnetic activity at that latitude in the upper Midwest.

Reminiscence of the late 1950s and the peak of cycle 19 continues to
generate email.  I'll let John Goewey, KI5IG of New Mexico tell it:

''During that peak K2UKN (Charles Groves) had a regular schedule with
JAs every noon time on 6 meters. I DXed a YL on 6 meters in MO while
I was WA2AJM in NJ. The YL had a curtain rod out the window, she
said. Another unusual contact was off my light bulb dummy load, in
the basement shack. QSO was 20 miles away, 6 meters as well. Yes, I
thought it was always going to be that way also.''

Emory Gordy, W4WRO was only 13 until the end of 1958, and writes, ''I
was first licensed in 1958, the era of the BIG ONE. Being a
novice-neophyte I, like others, innocently thought it would last
forever. The fact that it hasn't been repeated didn't dampen my
enthusiasm for ham radio''.

And last, Peter Hansen, W8TWA wrote: ''Having started my ham radio
activity as a Novice in 1954, I have seen the best and worst several
times now. One thing I miss is the two weekend ARRL DX contest.
Since the two weekends were separated by about a month, the March
weekend seemed to be a bit more exciting as we approached the
equinox. The two weekend contest was a great opportunity to observe
the changing conditions as winter came to a close. Maybe it was my
imagination, but it always seemed easier to work the polar path,
both long and short, to VU, UL, UH, UM, etc (excuse the old prefix
references.) in March than it was in February. And while there were
obvious variations in geomagnetic activity and availability of
stations between the two weekends, it always seemed that March was
better for that path. However, another contributing factor could
have been that we spent more time listening because many of the
stations had already been worked on the first weekend. To this day I
continue to monitor the flux, A, and K indices before the contest,
and find it of interest how that nuclear furnace 93 million miles
away continues to affect our everyday living, as well as its
influences on our hobby''.

If you would like to comment or have a tip, 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

Sunspot numbers for March 17 through 23 were 35, 37, 41, 39, 53, 49
and 56 with a mean of 44.3.  10.7 cm flux was 101.4, 96.5, 93, 89,
89.7, 87.3 and 87.7, with a mean of 92.1.  Estimated planetary A
indices were 12, 9, 14, 5, 8, 3 and 4 with a mean of 7.9.  Estimated
mid-latitude A indices were 8, 6, 9, 4, 5, 2 and 3, with a mean of


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