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ARRL Propagation Bulletin ARLP032 (2008)

ARLP032 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 32  ARLP032
From Tad Cook, K7RA
Seattle, WA  August 1, 2008
To all radio amateurs 

ARLP032 Propagation de K7RA

July ended with no sunspots at all, save for three days, July 18-20,
when one weak sunspot group appeared and faded from view.  Sunspot
numbers for those days were 11, 12 and 11.

This brings us to our practice of presenting the average daily
sunspot number for the past three months, then comparing it with a
monthly 3-month moving average for the past couple of years.  There
were 92 days in May, June and July, and 70 out of those 92 days had
no sunspots.  This brings us back toward the low of 3 from last
fall, centered on October.  The average daily sunspot number for the
last three months, centered on June, was just 3.7.

Jun 06 28.9
Jul 06 23.3
Aug 06 23.5
Sep 06 21.2
Oct 06 24.1
Nov 06 23.1
Dec 06 27.3
Jan 07 22.7
Feb 07 18.5
Mar 07 11.2
Apr 07 12.2
May 07 15.8
Jun 07 18.7
Jul 07 15.4
Aug 07 10.2
Sep 07  5.4
Oct 07  3
Nov 07  6.9
Dec 07  8.1
Jan 08  8.5
Feb 08  8.4
Mar 08  8.4
Apr 08  8.9
May 08  5
Jun 08  3.7

The outlook from the US Air Force Space Weather operations for many
weeks now has shown a predicted solar flux of 66, and their
prediction from July 31 shows the same, for the next 45 days.  This
tells me that there isn't any period where we might expect more
sunspot activity, or at least no way to foresee it.

They predict the next geomagnetic activity of any note for August
10, with a planetary A index of 20.  They predict a planetary A
index of 8 for August 1, then 5 for August 2-6, then 8 again on
August 7.

Geophysical Institute Prague echoes that prediction with quiet to
unsettled conditions for August 1 and 7, and quiet conditions August

In response to WD4ELG's comments in ARLP031, Jim Henderson, KF7E of
Queen Creek, Arizona has some interesting observations.

Jim writes, ''During these spotless and near-minimum flux conditions,
I have seen the extreme divergence of the day-to-day propagation
paths as a function of the traditional flux numbers.  Allowing for
seasonal trends, the differences in direction and quality of
openings on a given band from day-to-day where the flux and A and K
indices remain nearly unchanged for days, the openings generally
show much more relationship to the intensity of the solar wind''.

''From here, the patterns of propagation, under the weak stimulation
of near minimum flux, show much more pronounced linking to the
dynamic wind speed and composition than to simple 2800 MHz flux

''I believe without the positive contribution of the 'ionospheric
bias' provided by even a low flux, say 80-85, even a small increase
in solar wind has a profound effect on the daily paths''.

''Put another way, the good/bad effects upon propagation from minor
solar wind changes (not associated with flares and CMEs) are much
more observable when the flux is hovering under 68 or so than when
it is higher.  At that time, we feel the big effects from the major
storms.  But it is interesting to note the nuances of propagation
(say, by observing the NCDXF HF beacons daily) during a quiescent

Thanks, Jim.

Maurice Picard, W6FQS of Chico, California wrote: ''I noticed a
forecast on a propagation website
( that the geomagnetic
field would be unsettled due to a solar boundary crossing.  I don't
recall seeing reference to this phenomena in any previous forecasts.
What is this boundary crossing?''

Carl Luetzelschwab, K9LA provided us with this link explaining the

Carl will be writing the bulletin next week, for Friday, August 8,
while your regular author is out of town.  Carl will also be on the
road, travelling to Rochester, Minnesota for the W0DXCC Convention
(see at the Rochester Amateur Radio Expo.
Carl will post his bulletin from Dubuque, Iowa.  Check out Carl's
excellent propagation writings at

Another multi-hop sporadic E report from six meters, and this was
just last evening.  Dave Greer, N4KZ of Frankfort, Kentucky (EM78ne)
reports that beginning at 2322z on July 31, on 6 meter CW he worked
EA8/DL6FAW (Canary Islands) with good signals both ways.  At 2325z
he worked EA8AK on CW, and at 0026z on August 1 he worked EA8/DL6FAW
on SSB.

Dave reports that both stations made many U.S. contacts, but also
called CQ many times with no takers.  He thinks this is a good
example of distant six meter signals propagating to very specific
areas, but not others.  For instance, he saw that EA6SX in the
Balearic Islands was spotted on 50.105 MHz over several hours, but
Dave never heard him.

He also made Canary Island contacts in summer 2006 and 2007, again
working stations in pairs, but earlier in the season and earlier in
the day.  On June 18, 2006 he worked them around 1300z, and on July
15, 2007 around 2200z.

For six years his station has been on a hilltop (on Skyview Drive.)
with a very steep slope toward the East and Northeast.  He notes
that NW Africa is a real sweet spot for him on HF, with incredibly
strong signals to and from EA8, D4, CN and CT3.  This seems to be
true on 6 meters as well.  He runs 100 watts into a 4 element Yagi
at 60 feet.  His best 6 meter DX ever was in November 2001 when he
worked KH2GU in Guam, using an 80 meter horizontal loop antenna at a
previous QTH.

Bill Reichert, N9HH of Troy, Illinois reports 6 meter propagation
from earlier in the month.  On July 9, at 2342z while mobile from
EM58br he worked CT1HZE (Portugal, IM57nh) on 50.084 MHz using a
base-loaded quarter wave whip antenna.

A few days earlier around 1500z, CU2JT (Azores) called him, but QRM
from the East Coast prevented him from completing the contact.  This
was while Bill was mobile in Collinsville, IL.

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  Instructions
for starting or ending email distribution of this bulletin are at

Sunspot numbers for July 24 through 30 were 0, 0, 0, 0, 0, 0, and 0
with a mean of 0.  10.7 cm flux was 65.4, 65.8, 66.1, 66.3, 66.3,
66, and 66.5 with a mean of 66.1.  Estimated planetary A indices
were 11, 3, 5, 7, 7, 3 and 5 with a mean of 5.9.  Estimated
mid-latitude A indices were 7, 2, 4, 4, 6, 2 and 4 with a mean of


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