ARRL Propagation Bulletin ARLP025 (2007)

ARLP025 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 25  ARLP025
From Tad Cook, K7RA
Seattle, WA  June 15, 2007
To all radio amateurs 

ARLP025 Propagation de K7RA

In last week's Propagation Forecast Bulletin ARLP024, we had
erroneous solar flux values for June 5-6.  Instead of 88.8 on June
5, the solar flux was actually 81.2.  On June 6 the flux value was
84.6, not 87.1.  This means the average solar flux for May 31
through June 6 was actually 82.2, not 83.7.  If you use the WA4TTK
Solar Data Plotter, be sure to edit the values for those dates.

The solar flux numbers for two days of last week were estimated,
rather than actual, because there was a server change, and new data
was not at the old location on the web.  You can get to the new site
for the data via a shortened URL at,  The
official solar flux is the local noon reading, at 2000z, listed in
the fluxtime column of the table.  The fluxobsflux column holds the
three daily solar flux readings.  You can see a photo of the
observatory at,

This week's numbers at the end of this bulletin show that average
daily sunspot numbers for June 7-13 are down over 20 points,
compared to May 31 through June 6.  Average daily solar flux
declined over five points.

There has been another change in the prediction for smoothed sunspot
numbers for this year, and the latest figures show the cycle minimum
may have been three months ago, in March.

If you look at the previous forecast in the NOAA SEC Preliminary
Report and Forecast for May 1 at,, (check page 10 in issue
PRF 1652), the minimum smoothed sunspot number is 11, and it
stretches from January through June of this year.  But if you look
in the current June 12 issue on page 12, it shows the minimum of 11
for just one month, March 2007.

Check back issues of this bulletin at, for observations on smoothed sunspot
numbers, how they are calculated, and what they mean.  At, NOAA has a page on
smoothed sunspot numbers as well.

Dave Colton, VO1TK of St. John's, Newfoundland emailed comments
regarding recent conditions and activity on the bands.

Dave says, "Bands seem to be improving a little here lately. It
never ceases to amaze me how 15 meters seems to come alive whenever
there is a contest on but remain dormant otherwise. During the CQ WW
WPX contest, 15 was open well into the evening and past sunset. I
got into New Zealand with 100 watts and a wire antenna, again, on 15

Dave continues, "Several days ago, in the early evening, 20 meters
was open but uncommonly noisy. When I checked 40 meters however, it
was open and very, very quiet which is nothing short of a miracle at
my QTH."

I've noticed this as well, that frequently beacons demonstrate that
a band such as 15 or 17 meters is open to areas some distance away,
and propagation software has predicted it, but activity is low
enough when I'm on that it takes quite a bit of calling to raise
someone.  This is particularly noticeable when operating on a
weekday, rather than a weekend day.

Pat Hamel, W5THT of Long Beach, Mississippi experiments with 600
meters, which is the old 500 KHz maritime distress frequency, just
below the AM broadcast band.  At, you can see
details on the experiments, and location of the stations.  Don't
miss the link to the maps of reception reports, and another link to
photos of the stations, which can be viewed directly at,

For the next week, expect low sunspot activity and moderate
geomagnetic conditions.  Higher geomagnetic activity is predicted
for June 19 and again on June 22.  The US Air Force predicts the
planetary A index from June 15-24 (June 23-24 is ARRL Field Day) at
10, 5, 5, 10, 20, 15, 12, 20, 12 and 5.  Geophysical Institute
Prague predicts unsettled conditions for June 15, quiet to unsettled
on June 16-17, quiet on June 18-19, unsettled June 20, and unsettled
to active conditions on June 21.

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 June 7 through 13 were 59, 51, 19, 14, 13, 12
and 12 with a mean of 25.7. 10.7 cm flux was 85.5, 84.3, 78.6, 75.9,
73.3, 70.4, and 70.9, with a mean of 77. Estimated planetary A
indices were 3, 8, 8, 8, 2, 4 and 5 with a mean of 5.4. Estimated
mid-latitude A indices were 1, 7, 5, 6, 1, 3 and 5, with a mean of