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ARRL Propagation Bulletin ARLP028 (2013)

ARLP028 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 28  ARLP028
From Tad Cook, K7RA
Seattle, WA  July 12, 2013
To all radio amateurs 

ARLP028 Propagation de K7RA

Average daily sunspot numbers over the past week rose over 23 points
to 109.4, compared to the previous reporting week.  Average daily
solar flux was up nearly 21 points to 127.9.  Two days, July 6 and
July 10, had the most geomagnetic activity, with a planetary A index
of 25 on July 10.  Planetary A index on July 6 was 21.
The forecast issued on July 7 had a predicted solar flux of 145 on
July 11 and 12, and 150 on July 13 to 15, but alas, this has been
scaled back.  The latest forecast calls for solar flux at 110 on
July 12 to 14, then 105, 110, 115 and 120 on July 15 to 18, 125 on
July 19 and 20, then 120, 110 and 105 on July 21 to 23, 100 on July
24 and 25, 105 on July 26, 110 on July 27 and 28, then 120, 125 and
130 on July 29 to 31.
Predicted planetary A index is 8, 15, 25, 12, 8 and 10 on July 12 to
17, then 15 on July 18 to 21, 8 on July 22, 5 on July 23 to August
3, and 10 on August 4 and 5.
OK1HH of the Czech Propagation Interest Group has his own
geomagnetic forecast, and he foresees a mostly quiet geomagnetic
field on July 12, active to disturbed on July 13, quiet to active
July 14, quiet July 15, mostly quiet July 16, quiet to unsettled
July 17, quiet to active July 18, quiet to unsettled 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, quiet to unsettled July 27 and 28, quiet July 29 to
31, mostly quiet August 1, quiet to active August 2, active to
disturbed August 3, quiet August 4 and 5, and active to disturbed
again on August 6 and 7.
Carl Luetzelschwab, K9LA is now hosting the installation file for
the W6ELprop Propagation Prediction Program, which is free, and runs
on computers running the Windows operating system.  The file
disappeared from the W6EL web page, and now you can find it by going
to and clicking on Tutorials on the left side.  The
file is W6ELPropInst270.exe.
Ted Leaf, K6HI sent a link to an article about a large sunspot
group,  The
article says activity in the Sun's southern hemisphere is finally
picking up.  It goes on to claim that this could be an indication of
a double sunspot peak, with a second peak emerging as late as early
2014.  I would love to see our Sun peppered with energetic spots.
Unfortunately in this cycle, when they do emerge they tend to be
weak, evidence of the overall listless nature of this cycle.
K9LA talks about a second peak in his article from May 2013 at .
Several articles this week of interest to sun watchers:
The ON4AA site, not mentioned here in some time:
From N0NBH:
A real-time 160 meter propagation tool:
Sorry, no reports from readers this week.
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 4 through 10 were 109, 113, 115, 112, 143,
98, and 76, with a mean of 109.4.  10.7 cm flux was 137.7, 140.8,
134.2, 125.6, 119.3, 119.9, and 117.9, with a mean of 127.9.
Estimated planetary A indices were 5, 9, 21, 8, 6, 9, and 25, with a
mean of 11.9.  Estimated mid-latitude A indices were 4, 10, 20, 7,
7, 8, and 20, with a mean of 10.9.


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