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ARRL Propagation Bulletin ARLP013 (2007)

ARLP013 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 13  ARLP013
From Tad Cook, K7RA
Seattle, WA  March 23, 2007
To all radio amateurs 

ARLP013 Propagation de K7RA

For the past ten days we've observed no sunspots at all. Periods
like this, or longer, are expected at the bottom of the sunspot
cycle. As mentioned in a recent bulletin, the latest projection for
smoothed sunspot numbers from NOAA Space Environment Center has the
solar minimum at February through April 2007, with a smoothed
sunspot number of 11. You can see the table on page 10 of the
Preliminary Report and Forecast at,
Another way to look at it is that the minimum is projected between
December 2006 and July 2007, with a smoothed sunspot number of 12 or

Randy Crews, W7TJ notes that the graph at
tells the story on recent trends.

But reports still arrive weekly of operators working long distance,
even at the bottom of the cycle. Mike Carter, K8CN of Durham, New
Hampshire says he runs 50 watts CW into a wire 60 feet long and 20
feet at its highest. He's worked a lot of South Pacific DX on 40
meters from 1100-1200z, and Europe, Africa and the Caribbean on 30
meters around 2100-2300z.

The lower part of the HF spectrum is a good place to operate at the
bottom of the sunspot cycle. Unlike 10 or 15 meters, 160 and 80
meters won't be bothered by a low MUF (Maximum Usable Frequency), a
consequence of the lack of sunspots. With less solar activity comes
less problems with geomagnetic disturbances, which can be frequent
toward the top of the cycle.

Wednesday night about an hour after local sunset I operated 60
meters from my car, using one of those inexpensive popular
single-band mobile whips mounted on the trunk. This antenna can't be
very efficient, as the length is only about .045 wavelength. 60
meters is an unusual channelized band, with just 5 channels, the top
at just above 5.4 MHz. Upper-sideband SSB is the only permitted
mode, with transmit power limited to 50 watts ERP. The atmospheric
noise was high, and the static crashes probably from far-away

I made contact with Frank Miller, K9HMB of Harvard, Illinois, nearly
1700 miles to the east of me, and was surprised to receive an S9
signal report. Later, a glance at his antennas at told me what kind of station was receiving K7RA
so strongly. See if you can find the photo of a large commercial
crane "adding a third beam to the stack."

You can see more info on operating in the 60 meter band on the ARRL
web site at,

Dramatic solar images from the Japanese Hinode spacecraft prompted
numerous emails this week. The messages referred to a NASA article
at and a New Scientist article at, has a movie from the
spacecraft at or for today you can see it
at, Clicking on the movie URL should
launch a media player on your personal computer. I found the movie
better on the second viewing, because all of the content had been
buffered and the motion was smooth.

This weekend is the CQ World Wide WPX SSB Contest. There probably
won't be any sunspots, although a few are on the way. The sunspot
number will probably be 0 or 11. The higher frequencies won't be
fantastic, but geomagnetic conditions are expected to be stable and
quiet. The U.S. Air Force predicts a planetary A index for March
23-29 at 5, 5, 10, 15, 20, 10 and 5. Geophysical Institute Prague
says that March 23 should be quiet to unsettled, March 24-25
unsettled, March 26-27 unsettled to active, March 28 unsettled, and
March 29 quiet.

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 at, For a detailed
explanation of the numbers used in this bulletin see, An archive of past
propagation bulletins is at,
Monthly propagation charts between four USA regions and twelve
overseas locations are at,

Sunspot numbers for March 15 through 21 were 0, 0, 0, 0, 0, 0 and 0
with a mean of 0. 10.7 cm flux was 69.2, 68.7, 69.3, 70.5, 70.1,
72.6, and 72.8, with a mean of 70.5. Estimated planetary A indices
were 8, 10, 8, 3, 2, 2 and 2 with a mean of 5. Estimated
mid-latitude A indices were 5, 11, 8, 1, 1, 1 and 1, with a mean of


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