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ARRL Propagation Bulletin ARLP005 (2004)

ARLP005 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 5  ARLP005
From Tad Cook, K7RA
Seattle, WA  January 30, 2004
To all radio amateurs 

ARLP005 Propagation de K7RA

There are no sunspots. The visible solar disk is blank. This prompts
email inquiring if it's normal to see a spotless sun at this point
in the solar cycle. Yes, it is normal, because there are big
variations from day to day.

In order to generalize and see the larger trends, we need to
calculate a very smooth running average, where readings from many
days or months are averaged together. An example of a smooth chart
using running or moving averages of many data points can be seen on
the web at or

There is an explanation of how a smoothed sunspot number is
calculated based on 12 months of averaged data at, There is also a very
interesting graphic representation of the difference between a
running average based on 12 months and the averages for each
individual month over the same period at,

For the 12 months of data there is still a point on the graph for
each day, but that point represents all the data from 6 months
before and 6 months after, averaged together. The point for the next
day is the same, but drops one day off at the back end and averages
in another day's data from 6 months in the future. This is why
reports showing the current smoothed sunspot number always must be
at least 6 months in the past.

In that chart at the previous web link, those tiny colored diamonds
each represent a month of averaged data, just like those averages
presented frequently in this bulletin. An example of those monthly
averages is in 2003's Propagation Forecast Bulletin 49, at

Jeffrey Philpott, N6QYS wrote to ask if the solar cycle is near
bottom, and how long until conditions improve? If we look at the end
of a recent (January 6) issue of the NOAA Preliminary Report and
Forecast of Solar Geophysical Data at, it shows a
projection of future sunspot and solar flux values for nearly the
next four years, until December 2007.

This is a rough guess based on previous solar cycles. We can see
from both spreadsheets that the predicted bottom of the cycle is
expected to occur some time around the end of 2006, although given
what we covered above concerning long moving averages, we won't know
when the bottom occurs until some time after we've passed it.

We could assume that as we examine projections for rising values
during the next cycle, an estimate could be made for when conditions
should improve past the current level by looking for a value that
matches current conditions. Unfortunately, the data doesn't go that
far into the future. The best we can say is that a year from now
conditions should be worse, and that the projected number for
January 2005 doesn't rise back to that same level until December

Because January 2005 is a year from now, could we assume that
current conditions will worsen and not be at this level again until
December 2008? We can't really do that, because solar cycles tend to
rise faster than they decline, but a wild guess could be that some
time in 2008 conditions will be back up to where they are now.  We
can all make notes in our PDA to check back to this bulletin in 2008
and see if we were far off base. I've done this, and four years from
now I should be quite surprised to see this note from the past.

Conditions will likely improve somewhat over the next week. The
weekly average of daily sunspots for this week was half what it was
the week before. Average daily solar flux declined over 21 points.
Projected solar flux for Friday through Monday, January 30 through
February 2 is 90, 90, 100 and 100. Solar flux is expected to peak
for the short term around February 8.

Geomagnetic conditions may be rough over the next week, unsettled to
active. The predicted Planetary A index for January 30 through
February 5 is 15, 20, 20, 25, 25, 15 and 10.

Yesterday's ARRL DX Bulletin reported that this weekend is the UBA
DX SSB Contest. The CW section will be in February, but the target
in this competition is to work as many European stations on the five
non-WARC HF bands, and especially Belgian stations. Working Belgium
is worth 3 times the points counted for contacts with other European
countries. We won't hazard to guess when 80 and 40 meters should be
good for working Belgium or the rest of Europe, but here are some
projections for bands higher than 40 meters.

From Seattle, best conditions look to be on 20 meters after local
sunrise, 1630-1900z, and a weak possibility on 15 meters around
1630-1700z. There is another possible opening on 20, although not as
strong, after local sunrise at the European end around 0830-1000z.

From Southern California, conditions look best on 20 meters again
after local sunrise, from 1530-1900z, and around 1700z on 15.

From North Texas, conditions look best after local sunrise from
1400-2030z on 20 meters, 1530-1700z on 15 and possibly on 10 around

From Utah, check 20 meters around 1530-2000z.

From Nebraska and Kansas, the center of the contiguous 48 states,
check 20 meters around 1500-1930z.

From Chicago, check 20 meters after sunrise from 1400-2030z and 15
meters 1630-1830z.

From Ohio, check 20 meters after sunrise from 1330-2030z and 15
meters 1600-1800z.

Boston should have an excellent path around 1230-2000z on 20 meters,
and 1500-1730z on 15 meters.

Centered around the New York City area, the projection looks like
Boston's, except there is a greater chance of a 10 meter opening
around 1630-1700z. Philadelphia's prediction looks just like New
York City's.

Atlanta looks good from 1300-1930z on 20 meters and 1500-1630z on 15

South Florida should be good on 20 meters from 1230-2000z, 15 meters
1400-1700z, and possibly 10 meters around 1430-1600z.

Montreal, Quebec looks good on 20 meters from 1230-2030z and 15
meters around 1530-1730z.

Winnipeg, Manitoba looks good on 20 meters right at sunrise, from
1400-2000z. This is a polar path, so it could be especially affected
by geomagnetic activity.

Edmonton, Alberta is also a polar path, and 20 meter openings may
occur 1630-1930z.

South Central Alaska is also a polar path, and doesn't look very
good at all for 20 meters to Europe. There are only about 7 hours of
daylight at the Alaska end. The worst times look to be 0400-0600z on
20 meters.

Hawaii is so far from Europe that the openings have nothing to do
with sunrise at the KH6 end, but look good on 20 meters after
sunrise at the Belgium end, 0800-1330z.

From Japan, the openings look long, 0630-1800z on 20 meters,
0830-0900z on 15 meters, and possibly 10 meters around 0800z.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the Propagation page on the
ARRL Web site at

Sunspot numbers for January 22 through 28 were 76, 62, 47, 48, 38, 0
and 0 with a mean of 38.7. 10.7 cm flux was 121.8, 115.2, 107.5,
102.3, 98, 93.7 and 88.5, with a mean of 103.9. Estimated planetary
A indices were 62, 38, 15, 33, 17, 16 and 19, with a mean of 28.6.


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