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ARRL Propagation Bulletin ARLP043 (2009)

ARLP043 Propagation de K7RA

Propagation Forecast Bulletin 43  ARLP043
From Tad Cook, K7RA
Seattle, WA  October 23, 2009
To all radio amateurs

ARLP043 Propagation de K7RA

A tiny cycle 24 sunspot group numbered 1028 emerged briefly on
Tuesday, October 20, then was gone.  This is another brief phantom
sunspot, teasing us with hints of the expected increase in activity
that never seems to manifest.  Of course the silver lining in the
low solar activity is low geomagnetic activity.  While folks in
Alaska miss dramatic aurora, HF hams in the northern latitudes can
enjoy the bands without all the disruption that comes with
geomagnetic storms.

A couple of coronal holes are spewing enough plasma to activate some
aurora, but remember that most of the photos you see of beautiful
displays in the sky are actually very long exposures taken from a
rock-steady tripod mount.  Many times the unaided eye cannot
perceive the more dramatic details.  As a result of solar wind from
coronal holes, geomagnetic indices rose yesterday, on Thursday, with
planetary A index at 14, mid-latitude A index as measured in
Virginia at 12, and the College A index at Fairbanks, Alaska way up
to 25.

The College A index has been quiet for a long time, and the last
time the index was nearly this high was on August 30, 2009 at 24.
Prior College A index readings higher than Thursday's were July 22,
2009 at 27, February 4, 2009 at 36, December 6, 2008 at 26, and
November 8, 2008 at 30.

You can look back at daily geomagnetic and solar indices from 1994
to the present at
In fact, it is instructive when bemoaning the present
lack of solar activity to reflect on times when there was so much
geomagnetic activity, that HF propagation was difficult.  At
see 1994 College and Planetary A index numbers, and how there were
extended periods of heightened activity.  In fact, you can see
stretches for weeks at a time when there are only spotty records of
the College A and K index, and I seem to recall that during these
times their instruments were knocked out of service by energy from
geomagnetic storms concentrated in polar regions.

The activity on Thursday was not predicted by USAF and NOAA in their
daily 45-day forecast at  In the days
prior to Thursday (check October 20 and 21) they were still
expecting a Planetary A index of 5 for Thursday.  Then in the
October 22 prediction they show a Planetary A index of 8 for October
23-25, the weekend for the CQ World Wide SSB DX Contest.

Geophysical Institute Prague has a little more detailed forecast for
the contest weekend.  They expect quiet conditions for October 23,
quiet to unsettled October 24, unsettled on October 25, and back to
quiet for October 26-29.  OK1HH of the Czech Propagation Interest
Group expects a bit higher activity, with quiet conditions for
October 23, and unsettled to active geomagnetic conditions for
October 24-25.

Scott Craig, WA4TTK has an updated data file for his Solar Data
Plotting Utility.  This is useful if you are not yet running the
program and collecting the data.  The data can be updated
semi-automatically each week from this bulletin, and manually as
well.  The new data file has daily solar flux and sunspot numbers
from January 1, 1989 through October 7, 2009.  Download it for free
at  This is a good way to
visually realize the difference between the previous solar minimum
and this extended quiet period we are in.

Brian Webb, KD6NRP of Ventura County, California notes that even
with no sunspot activity, using low power and a simple antenna he
hears and works many stations overseas on 17 meters.  On October 19
at 1556z he worked PA3HP on PSK on 17 meters, after answering his
CQ.  Brian's antenna was a horizontal delta loop, about 50 feet on
each side, and fed with 300 ohm twinlead and 100 watts.  I noted
that between his location and the Netherlands on that date there was
a good chance of an opening from 1600-1730z, according to W6ELprop.

Ed Stokes, W1KOK of Randolph Center, Vermont asks if there is a
W6ELprop version for Macintosh.  No, there isn't, although Ed says
he would like to port it to Mac.  In the 2008 ARLP049
( we answered a
similar question, and were pointed toward DX Toolbox at, and also a
site at for
Macintosh ham radio software.

This week an interesting piece about sluggish flow inside the sun
appeared, authored by two scientists on the GONG project.  Read it

Carl Luetzelschwab, K9LA, has another monthly column on propagation
in the latest November issue of the now online-only WorldRadio
Magazine.  It is free, and you can download it in small parts or one
big file at  Just click on
the big WorldRadio Online button.  Carl's column this month is on
Short-path Summer Solstice Propagation, and begins on page 22.  Also
from that page you can click a link to see the rules for the CQ
World-Wide DX Contest this weekend (Phone) and November 28-29 (CW).

Next week K7RA will be on the road, and it probably won't be
practical to get the bulletin to Newington by Friday morning.
Instead, we expect to have Steve Nichols, G0KYA of Wymondham,
England pitching in.  Steve is on the Propagation Studies Committee
of the Radio Society of Great Britain.  Steve was the author of the
PowerPoint presentation on WSPR he gave at the RSGB convention,
which we referenced in last week's bulletin.

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 October 15 through 21 were 0, 0, 0, 0, 0, 11,
and 0 with a mean of 1.6.  10.7 cm flux was 70.4, 69.6, 70.7, 70.1,
70.9, 71, and 71.3 with a mean of 70.6.  Estimated planetary A
indices were 4, 4, 2, 1, 1, 1 and 1 with a mean of 2.  Estimated
mid-latitude A indices were 3, 3, 0, 0, 1, 0 and 1 with a mean of


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