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ARRL Propagation Bulletin ARLP032 (2016)

ARLP032 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 32  ARLP032
From Tad Cook, K7RA
Seattle, WA  August 5, 2016
To all radio amateurs 

ARLP032 Propagation de K7RA

Average daily sunspot numbers dropped from 19.3 last week to 10.7 in
the current reporting week, July 28 through August 3. Average daily
solar flux declined from 82.5 to 72.1.

Geomagnetic indices were more active this week, with average daily
planetary A index increasing from 8.7 to 13, and mid-latitude A
index rising from 8.9 to 11.9.

Sunspot numbers were low all week, and on Wednesday August 3 the
sunspot number dropped to 0, as in no sunspots. And there were still
no sunspots the next day, August 4.

Predicted solar flux is 80 on August 5-7, then 85, 90 and 95 on
August 8-10, 100 on August 11-12, 95 on August 13-15, 90 on August
16-17, then 85 and 80 on August 18-19, 75 on August 20-22, 70 on
August 23-27, 72 on August 28-30, 75 on August 31, 85 on September
1, 90 on September 2-3, then 95 on September 4-11 and 90 on
September 12-13.

Predicted planetary A index is 15 on August 5-6, then 10, 20, 8, 12,
10 and 8 on August 7-12, 5 on August 13-14, 12 on August 15-16, 5 on
August 17, 8 on August 18-19, 5 on August 20-23, 15 on August 24-25,
5 on August 26-27, 8 on August 28, 20 on August 29-30, 15 on August
31, 12 on September 1, 10 on September 2-3, then 8 and 5 on
September 4-5, 12 on September 6-7, 8 on September 8, 5 on September
9-10 and 12 on September 11-12.

Geomagnetic activity forecast for the period August 5-August 31,
2016 from OK1HH of the Czech Propagation Interest Group.

Geomagnetic field will be:
Quiet on August 13-14, 23, 27-28
Mostly quiet on August 22
Quiet to unsettled on August 5, 9, 11-12, 15, 18, 24, 31
Quiet to active on August 6, 10, 20, 25-26, 30
Active to disturbed on August 7-8, (16-17, 21,) 29

Increasing solar wind from coronal holes are expected on August 5-8
(- 9), 14, 22-23, 29-30

Parenthesis means lower probability of activity enhancement.

"The Times of India" has an article on solar flares at, .

Howard Schler, K2EQ of Ovid, New York wrote:

"I wanted to point out one oddity of propagation that has been
occurring on a daily basis for many weeks though now a bit less.

"On 20 Meters, each day between midnight local time 0500z to about
0630z or 0700z, PSK is almost completely dead, less than a handful
of stations and most very weak and broken up.

"However, the surprising exception is that in the midst of that I
have been able to work VKs, ZLs and other South Pacific stations
from my home in New York with good to excellent signals, sometimes
10,000 miles away and the only signal on the PSK spectrum.  We both
marvel at the propagation and how odd it is yet how strong our
signals are.  I do not understand propagation beyond a very
fundamental level.  Nonetheless, there it is and I'm up way past my
bedtime almost every night calling into a blank noisy band, with
surprising results."

Often when a band seems dead, you can call CQ and find out there is
good propagation, but you haven't heard anyone calling, so it seems
like there is no propagation.

Around that time from your place to ZL on 20 meters should be an
excellent path, according to some path projections I ran with

Looks like the path opens up about 0230 UTC, and an hour later is
about 5 dB better. Signals slowly climb til 0530, then level off,
and then start to fade after 0700. But on some days there could be
strong signals til 1130 UTC.

Time to look at our 3 month moving average of sunspot numbers, now
that July is over. The moving average ending in January through July
was 55.4, 53.5, 49, 45.3, 43.1, 35.4 and 33. Looks like a steady
decline in solar activity, although I am surprised to see so many
zero sunspot days at this point in the declining cycle.

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

Monthly propagation charts between four USA regions and twelve
overseas locations are at

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Sunspot numbers for July 28 through August 3 were 13, 13, 13, 12,
13, 11, and 0, with a mean of 10.7. 10.7 cm flux was 70.3, 70.5, 71,
71.5, 71.9, 74.9, and 74.8, with a mean of 72.1. Estimated planetary
A indices were 15, 14, 6, 3, 3, 17, and 33, with a mean of 13.
Estimated mid-latitude A indices were 13, 16, 7, 2, 4, 17, and 24
with a mean of 11.9.