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ARRL Propagation Bulletin ARLP029 (2013)

ARLP029 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 19, 2013
To all radio amateurs 

ARLP029 Propagation de K7RA

Unsettled geomagnetic conditions continued this week, punctuated by
periods of relative quiet.  The most active days were July 14 and
15.  The planetary A index was 20 and 25, and the mid-latitude A
index was 15 and 33 on those dates.  Of course Alaska's College A
index was higher, at 58 and 34.
The A index is a daily value, and it is calculated from eight
measurements per day (once every three hours) of the K index.  The K
index is a quasi logarithmic value based on magnetometer readings,
so each one-point change represents a large difference.  The K index
is averaged into the daily A index, a linear scale.  This gives a
pretty good explanation:
Note the graph labeled "The relationship between K and A."
The planetary A index is based on the planetary K index, which is
derived from readings at a network of geomagnetic observatories.
The mid-latitude K and A index are from a single magnetometer at
Fredericksburg, Virginia, near the intersection of Observatory Road
and Magnetic Lane, inside the Fort A.P. Hill Army base, about 8
miles southeast of downtown Fredericksburg, Virginia.
You can sometimes find street names with appropriate references
where magnetometers are located, for instance, Geophysical
Observatory Road for the magnetometer at Newport, Washington, near
48.27 degrees north, 117.13 degrees west.
Over the past week, the average daily sunspot number declined nearly
33 points to 76.9, while average daily solar flux was down 14 points
to 113.9.  The average planetary A index barely moved, while the
average mid-latitude A index rose two points to 12.9.
But yesterday (Thursday, July 18) the sunspot number jumped to 112,
far above the average for the previous seven days.
The latest forecast shows solar flux at 120 on July 19, 125 on July
20 and 21, 120 on July 22 and 23, then 115, 110 and 105 on July 24
to 26, 110 on July 27 and 28, then 120, 125 and 130 on July 29 to
31, 135 on August 1 and 2, then 130, 125, 130 and 135 on August 3 to
6, 140 on August 7 and 8, 135 and 120 on August 9 and 10, 125 on
August 11 and 12, 120 on August 13, and 125 again on August 14 to
16.  It then declines to a minimum of 100 on August 20 and 21,
before rising again.
Predicted planetary A index is 20 on July 19 and 20, 15 and 10 on
July 21 and 22, 5 on July 23 to 25, then 30 and 10 on July 25 to 27,
5 on July 28 through August 3, 10 on August 4 and 5, 15 and 8 on
August 6 and 7, 5 on August 8 to 12, 10 on August 13, and 15 on
August 14 to 17.
Petr Kolman, OK1MGW sends a geomagnetic forecast from the Czech
Propagation Interest Group.  He says that a growing solar wind "may
cause remarkable changes in the magnetosphere and ionosphere on July
19 to 22 and 25 to 28."
He predicts quiet to active geomagnetic conditions on July 19,
active to disturbed July 20, quiet to active July 21, quiet to
unsettled July 22, quiet July 23 and 24, quiet to unsettled July 25,
quiet to active July 26 and 27, quiet to unsettled July 28, quiet
July 29 to 31, quiet to unsettled August 1, quiet to active August
2, active to disturbed August 3, quiet August 4, mostly quiet August
5, active to disturbed August 6 and 7, and quiet to unsettled August
8 to 10.
At 2330 UTC on July 17 Australia's IPS Radio and Space Services sent
a geomagnetic warning, predicting unsettled to active conditions
July 18, active with minor storm periods July 19, and quiet to
unsettled conditions July 20.
Just after last week's bulletin ARLP028 was issued, Bruce Smith,
AC4G of Taft, Tennessee sent in this report:  "Just wanted to report
a 6 meter sporadic E opening on the morning of July 12 (finally)
into EM65 from 0630 AM to 0830 AM CDT just after sun rise.  Signals
topped out at approximately S-5 with most QSOs made while receiving
stations with S-2 signals.  The following EU stations were worked or
heard by this station during the time range given: EA1EJ, S57RR,
special event station down in the Florida Keys, K4N (EL84).  Glad to
have made several EU QSOs on 6 meters for the first time this year
with my moderate setup using a 5 element Yagi and 100 watts.  Still
looking for Africa, Asia, and the Pacific."
Keith Reedy, WA9DRO of Terre Haute, Indiana reports from last week,
"One of my favorite bands is 12 meters.  Not much joy on that band
lately, just a few openings from time to time state side.  However I
did hear an Israeli station on 24.964 MHz last Monday evening July 8
at about 8 PM local time.  I am using a 3 element beam at about 35
feet.  What does this mean, don't know, but, I hope more of the
David Moore sent a link to this Los Angeles Times article about the
current weak solar cycle:,0,6978639.story

The article presents an interesting observation about weak solar
cycles in the early part of any century.  Note they corrected a typo
in the original article which confused astrology with astronomy.  Oh
Elwood Downey, WB0OEW of Tucson, Arizona sent a similar article,
about the weak peak:
Pat Hamel, W5THT of Long Beach, Mississippi wrote on July 15, in an
email titled "Frustrating propagation modes", "The red lines on the
maps show it was a super weekend for part of the country on six
meters.  I have spent part of today (until they packed up),
Saturday, and Sunday listening on the K4N six-meter announced
frequencies.  I am too close to them.  I kept getting what sounded
like meteor pings.
This is one of the benefits (?) of living in the middle of the Gulf
Coast.  If the weather would have been foggy all the way across the
gulf, I would have had a pipeline."
Perhaps he was referring to maps here:
Or here:
Jeff Hartley, N8II of Shepherdstown, West Virginia wrote on July 15:
"E-skip has been down this year compared to normal, but at least the
6 meter Es openings are a bit more frequent with several multi-hop
to the west and one to EU/Northern Africa along with another to EA8
only.  15 and 17 seem down quite a bit from June.  It has been tough
to work the county hunter mobiles on 17 quite often out in the upper
Midwest and Montana/Wyoming/Colorado.
The IARU contest was about as expected with some fun to be had from
big PVRC stations operating as NU1AW/3 (IARU HQ) and W1AW/4.  I was
at NU1AW/3 from N3HBX (signing the /3 was a pain over hundreds of
times).  But, it was a lot of fun being a multiplier for everyone.
40 opened fairly early to EU with some very strong signals from the
big guns in EU and the little guys in the QRN.  Northern Europe was
weak and watery for the most part but we did log about 4 Asiatic
Russians on the west edge in zone 30.
75 phone was pretty good to Europe with rather poor activity.  The
HQ stations from Chile and Argentina called in with decent signals.
There was enough North American activity to keep us fairly busy thru
0500Z and the Yagi fixed at 300 degrees helped a lot with zone 6.
Only one zone 2 (VE6) and one zone 3 (VE4) called in along with
VA3RAC and several VE2's and 3's.  Most signals were loud enough to
be heard easily through the constant S9+ QRN.
20 was the "money band" with very good 1000+ QSO totals from us on
phone and the usual 20 meter CW team from DX contests at W3LPL
operating 2 interlocked radios picking off QSO's in between CQ's as
we were doing as well.  We had the usual good 20 meter opening
around European Russia sunrise and after 0200-0400Z."
Steve Long, AC6T of Santa Barbara, California notes "As an
occasional 6 meter fan, I have noticed this past 2 months that the
Midwest, East Coast and even Pacific Northwest have enjoyed terrific
multihop ES propagation all over the country.  Also, frequent
openings to Japan and Europe.  I'm puzzled (not to mention
disappointed) why my corner of DM04 (Santa Barbara) and Southern
California in general have had so few decent openings.  6 meters has
been a great white noise source nearly all summer.  Even Arizona
seems to do better than we do.  Any wisdom as to why this might be?"
I have NO idea.  Happenstance?
Maybe the activity during the CQ Worldwide VHF Contest this weekend
will change the 6 meter fortunes of Southern California.  See for more information.
For more information concerning radio propagation, see the ARRL
Technical Information Service at  For an explanation of
the numbers used in this bulletin, see  An archive of
past propagation bulletins is at  More good
information and tutorials on propagation are at
Monthly propagation charts between four USA regions and twelve
overseas locations are at
Instructions for starting or ending email distribution of ARRL
bulletins are at
Sunspot numbers for July 11 through 17 were 85, 87, 66, 88, 77, 61,
and 74, with a mean of 76.9.  10.7 cm flux was 113.4, 117.6, 114,
112.9, 114.1, 113.9, and 111.3, with a mean of 113.9.  Estimated
planetary A indices were 18, 9, 10, 20, 25, 5, and 5, with a mean of
13.1.  Estimated mid-latitude A indices were 15, 9, 8, 15, 33, 5,
and 5, with a mean of 12.9.


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