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ARRL Propagation Bulletin ARLP028 (2007)

ARLP028 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 28  ARLP028
From Tad Cook, K7RA
Seattle, WA  July 6, 2007
To all radio amateurs 

ARLP028 Propagation de K7RA

The average daily sunspot number for this week rose nearly 18 points
from the previous seven days.  On July 4 the A index was moderately
elevated due to a solar wind stream.  Expect to see a similar
increase around July 11, and a much greater increase in geomagnetic
activity from July 16-19.

Geophysical Institute Prague predicts quiet conditions for July 6-9,
quiet to unsettled July 10, and unsettled conditions for July 11.

Monthly averages of daily sunspot numbers for April 2006 through
June 2007 were 55.2, 39.6, 24.4, 22.6, 22.8, 25.2, 14.7, 31.5, 22.2,
28.2, 17.3, 9.8, 6.9, 19.8 and 20.7.  Monthly averages of daily
solar flux for the same period were 88.9, 80.9, 76.5, 75.8, 79,
77.8, 74.3, 86.3, 84.4, 83.5, 77.7, 72.2, 72.4, 74.4 and 73.7.

Looking at 3-month smoothed sunspot numbers, knowing the June
numbers we can add them to April and May to show the three-month
average centered on May.

Here are the 3-month smoothed sunspot numbers based on data from the
past 22 months:

Oct 05 28
Nov 05 36 
Dec 05 40.6 
Jan 06 32.4 
Feb 06 18.1 
Mar 06 27.7 
Apr 06 38.5 
May 06 39.7 
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

Why do we say 22 months when only 20 months are shown?  This is
because these numbers are based on data from September 2005 through
June 2007.  The months shown are the center of each three month
average of daily sunspot numbers.

Notice the averages centered on December 2006 through May 2007.  If
we narrowly focus on just these data, it sure looks like the cycle
reached a minimum centered on March 2007, rising since then.  Note
also from the monthly averages above that the June average at 20.7
is nearly five points higher than the 3-month average centered on

Look on page 9 in the July 3 Weekly Preliminary Report and Forecast
at and note the cycle
minimum is shown as March 2007, the same month that our three-month
average shows.  This table is of actual and predicted smoothed
sunspot numbers, each based on a year of data.  December 2006 is
based entirely on known data, January 2007 is based on known data
plus one month of predicted data (July), February is based on two
months of predicted data (July and August) and the rest known data,
and so on.

More 6 meter and Field Day reports came in this week.  Several Field
Day stations had a lot of luck on 15 meters, and they tended to be
in the Midwest and the South.  Dustin Cox, KE5NKG of New Mexico said
that on Field Day he had a great overnight run on 15 meters.

There was a great deal of 6-meter activity in the final week of
June.  On June 25 John Butrovich, W6UWB of Orange Grove, Texas
(EL17ax) worked 20 European stations, mostly UK using the
weak-signal JT6M mode on 50.257 MHz.  For more info on JT6M, see and

On June 25, K0GU in Wellington, Colorado (DN70mq) worked 18 European
six-meter stations, and a few more the next two days.  K3MSB of
Airville, Pennsylvania worked a number of West Coast 6-meter
stations, and on June 27 worked IK2GSO on CW at 2156z.  W9IND of
Indianapolis reported that his club's six meter beacon, W9VW was
heard in Scotland, with propagation from EM69 to IO75.

Also in EM69, KJ9C had great luck on 6 meters late in the afternoon
on June 29, working several Europeans on CW.  He wonders why more
overseas stations don't try 6 meter CW, and notes ''The Caribbean
guys seem to be stuck on SSB.''

Dick Battle, AK4RB in FM06 in North Carolina was thrilled to work
WW2R in North Texas (EM03) for his first ever 6 meter QSO on June
30.  Dick does not have a 6-meter antenna, but used an antenna tuner
to load his HF wire doublet hidden in the attic of his townhouse.
On June 26 Kevin Blanton, KE5DUK in Beebe, Arkansas(EM34) worked his
first long-distance 6 meter contact using FM simplex on 52.525 MHz
and talked to someone in FN06 in Ontario.  He also worked New York,
Tennessee, North Dakota and Pennsylvania.

There were many more 6-meter reports this week, too many to mention

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 June 28 through July 4 were 27, 29, 36, 30, 13,
12 and 13 with a mean of 22.9. 10.7 cm flux was 74.9, 75.3, 74,
74.3, 72.6, 71.7, and 72.4, with a mean of 73.6. Estimated planetary
A indices were 6, 13, 6, 5, 3, 9 and 16 with a mean of 8.3.
Estimated mid-latitude A indices were 5, 5, 4, 4, 2, 6 and 13, with
a mean of 5.6.


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