ARRL Propagation Bulletin ARLP030 (2007)

ARLP030 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 30  ARLP030
From Tad Cook, K7RA
Seattle, WA  July 20, 2007
To all radio amateurs 

ARLP030 Propagation de K7RA

This week saw an increase in average daily sunspot numbers, rising
over 8 points to 29.3.  Expect to see a lower average for next week,
with perhaps some zero-sunspot days.  Perhaps early August will have
sunspot numbers back in the twenties at least.  Currently sunspot
963 is disappearing from view.

Right now there is a solar wind stream headed toward our planet.
This should only be a minor upset, with planetary A index around 15
for today and tomorrow, July 20-21.  Currently the IMF
(interplanetary magnetic field) points south, which makes us

Geophysical Institute Prague predicts unsettled to active conditions
for July 20, unsettled July 21, quiet to unsettled July 22, quiet
for July 23-25, and unsettled July 26.

Check out the July 2007 issue of Sky and Telescope, for an article
titled ''Solar Forecast:  Storm Ahead''.  Thanks to K9LA, EI4HQ, and
AI4VV for the tip, and to N7SO for mailing a copy.  The article
discusses predictions for the next solar cycle, different methods
for predicting it, and the hazards for space travel and
communications from solar events.

Scott Avery, WA6LIE of Salinas, California (CM96) reports fantastic
conditions on six and two meters last weekend.  On July 14 from
1600-2100z six meters sounded like 20 meters on a good day, and he
could work all over the East Coast, ''Maryland, Carolinas, Florida
and everything between.''  At one point he heard a Colorado station
declare that E-skip was coming in on 2 meters, so he swung his
13-element Yagi toward the east.  He heard K0GU, N0VSB and KC0COU
with signals above S9.  He also worked out of state when he switched
from 45 watts and the Yagi to 5 watts and a vertical. Several other
stations in CM96 with low power and simple 2-meter antennas also had
good results.

Steve Miller, N0SM of Ottumwa, Iowa (EN30) has a response to the
recent comments from K0MHP about six meters, magic band or invisible
band.  He writes, ''There have been openings if one can catch them
but part of it is living in the proverbial Black Hole of the
Midwest. We occasionally get stations from the Caribbean and on rare
occasions some European stations.  The really successful Midwest ops
on 6 have to study propagation  patterns very carefully and even
then a big dose of good luck goes with it.  An excellent radio and
antenna system are also vital.  But in general, many of us share his

William Henry, W8QP of Morgantown, West Virginia asked about graphs
of sunspots covering several centuries, back to the first recorded
sunspot counts.  You can find them at

Stan Horzepa, WA1LOU wrote recently in his Surfin' feature on the
ARRL web site about Long Delayed Echoes.  You can find the LDE
stories listed under L in this index, at  In the latest piece, he
mentions one of those baffling, ''unexplainable'' stories about a
television signal received several years after the original
transmission, which is a tale that I heard as a child.  In this
case, the ''ghost'' transmission was from a station off the air for
several years, with the signal supposedly wafting around the
universe at a velocity much slower than the speed of light.  Often
this kind of thing, like many UFO stories, becomes much less
mysterious yet more interesting if you can find additional facts,
and perhaps another perspective.  I offer two of those, here: and here: .

In last week's bulletin ARLP029, the dates for the numbers at the
very end were misstated as June instead of July.  Just changing the
word June to July will get you on the right track.  But if you use
WA4TTK's Solar Data Plotting Utility, which can grab the data out of
a text file, not only did you not get the numbers for the week, but
the nifty automatic updater has messed up your data file.  To
correct this, you can make the change to last week's bulletin, then
grab the data using the Utility, then to correct the bad data from
June, update numbers from ARLP024 and ARLP025.  A source for past
bulletins is at the end of this bulletin.

However, you can avoid that trouble by downloading a new corrected
graph.dat file from the WA4TTK web site, which will give you all of
the sunspot and solar flux data from the start of 1989 through the
eleventh of this month.  The software and the data file are free at  The data file is also useful
with a spreadsheet program, and you can use the free plotting
software to automatically update the data weekly.

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 July 12 through 18 were 25, 38, 41, 41, 30, 17
and 13 with a mean of 29.3.  10.7 cm flux was 76.9, 78, 75.7, 74.7,
72.9, 72.3, and 69.6, with a mean of 74.3.  Estimated planetary A
indices were 8, 4, 23, 13, 6, 5 and 3 with a mean of 8.9.  Estimated
mid-latitude A indices were 6, 5, 12, 11, 4, 2 and 3, with a mean of