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ARRL Propagation Bulletin ARLP038 (2015)

ARLP038 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 38  ARLP038
From Tad Cook, K7RA
Seattle, WA  September 18, 2015
To all radio amateurs 

ARLP038 Propagation de K7RA

Solar activity is perking up this week.  Average daily solar flux
rose from 85.3 last week to 97.3 this week (September 10-16).
Over the same two weeks, average daily sunspot numbers rose from
37.3 to 66.9.
The latest forecast from USAF/NOAA shows solar flux at 110 on
September 18-20, 105 on September 21-22, 100 on September 23, 95 on
September 24, 90 on September 25-26, then 85, 80 and 85 on September
27-29, then 90, 95 and 90 on September 30 through October 2, 85 on
October 3-6, then 90 and 95 on October 7-8, 100 on October 9-10, 105
on October 11-12, then 100 and 95 on October 13-14, and 90 on
October 15-23.
Predicted planetary A index is 8, 12, 16, 8 and 6 on September
18-22, 5 on September 23-24, 10 on September 25, then 5 on September
26-29, 8 and 18 on September 30 through October 1, then 25, 20 and
12 on October 2-3, then 25, 20, 18, and 12 on October 4-7, then 18,
15, 10, 12, 20 and 12 on October 8-13 and 8 on October 14-15.
F.K. Janda, OK1HH of the Czech Propagation Interest Group (who has
been providing weekly forecasts with OK1MGW since 1978) sends along
his geomagnetic forecast, which sees quiet to active conditions
September 18-19, mostly quiet September 20, quiet on September 21,
active to disturbed September 22, quiet to active September 23-24,
quiet to unsettled September 25, mostly quiet September 26, quiet
September 27-28, mostly quiet September 29, quiet to active
September 30 through October 1, quiet to unsettled October 2, quiet
to active October 3, active to disturbed October 4-5, quiet to
active October 6, quiet to unsettled October 7, active to disturbed
October 8, quiet to active October 9, mostly quiet October 10, quiet
to active October 11, active to disturbed October 12, quiet to
unsettled October 13 and mostly quiet on October 14.
He sees increases in solar wind on September 18, 20-22, 25-28,
October 3-5 and 8-9, but is less certain about the September 18 and
25-28 periods.
Cecil Williams, NW8F of Wheelersburg, Ohio asks "Is this cycle
nearing its end and what can be expected this Fall/Winter for 80 and
160 meters? The bands are starting to have a lot more DX it seems.
Yesterday I heard D67GIA on 20 meters (later on 15 meters) and he
had a decent signal."
No, this solar cycle (number 24) is just past the peak, which was in
Spring 2014. The next solar minimum may be coming around 2019 or
You can see the predicted sunspot numbers out through the end of
2019 here, in the table on page 13:
While solar activity has been slightly higher this week, Cecil may
be noticing a seasonal change in conditions as the Autumnal Equinox
approaches next week on Wednesday, September 23.
If we do a prediction for 20 meters from Cecil's station to Comoros
using W6ELprop, and compare current conditions to conditions on
August 1, there is a big difference in the length and quality of the
openings, with marked improvement as we approach the Equinox.
Also, if solar activity continues to decline, this should be good
for 80 and 160 meter conditions.
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 web page 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
My own archives of the NOAA/USAF daily 45 day forecast for solar
flux and planetary A index are in downloadable spreadsheet format at and .
Click on "Download this file" to download the archive and ignore the
security warning about file format. Pop-up blockers may suppress
download. I've had better luck with Firefox than Internet Explorer.
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 September 10 through 16 were 42, 79, 87, 75, 52,
66, and 67, with a mean of 66.9. 10.7 cm flux was 83.5, 92.8, 99.1,
98.8, 96.5, 101.1, and 109.4, with a mean of 97.3.  Estimated
planetary A indices were 13, 59, 16, 11, 14, 18, and 12, with a mean
of 20.4.  Estimated mid-latitude A indices were 10, 36, 13, 8, 10,
17, and 9, with a mean of 14.7.


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