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ARRL Propagation Bulletin ARLP030 (2017)

ARLP030 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 30  ARLP030
From Tad Cook, K7RA
Seattle, WA  July 28, 2017
To all radio amateurs 

ARLP030 Propagation de K7RA

All of the indicators we track at the bottom of this bulletin fell
last week.
Because there were no sunspots in six of the seven days (July 20 to
26) last week, average daily sunspot number dropped from 26.6 to
1.7.  Average daily solar flux declined from 85.9 to 69.7.
Average daily planetary A index declined from 13 to 11.9, while the
mid-latitude A index went the opposite direction, from 10.9 to 12.9.
The latest predicted solar flux (as of July 27) shows 68 on July 28
and 29, 72 and 76 on July 30 and 31, 80 on August 1 to 3, 82 on
August 4 to 11, 80 and 75 on August 12 and 13, 70 on August 14 to
25, 80 on August 26, 82 on August 27 through September 1, 80 on
September 2 to 4, 82 on September 5 to 7, and 80, 75 and 70 on
September 8 to 10.
Predicted planetary A index is 7, 5, 6, 12, 10 and 8 on July 29
through August 2, 5 on August 3 to 5, 25 and 10 on August 6 and 7, 5
on August 8 to 15, 15 on August 17 and 18, then 12 and 8 on August
19 and 20, 5 on August 21 to 31, then 25, 10 and 8 on September 1 to
3, and 5 on September 4 to 10.
F. K. Janda, OK1HH of the Czech Propagation Interest Group sent this
geomagnetic activity forecast for the period July 28 to August 22,
Geomagnetic field will be: 
Quiet on August 4, 9 
Mostly quiet on July 30, August 2, 8, 10, 14 and 15 
Quiet to unsettled July 28 and 29, August 1, 3, 16 
Quiet to active on July 31, August 5, 7, 11, 13, 17 to 22 
Active to disturbed on August 6, 12 
Amplifications of the solar wind from coronal holes are expected on
July 13 to 16 (-17), 20 and 21, (23 and 24, 28 and 29,) August 6 to
- Parenthesis means lower probability of activity enhancement and/or
lower reliability of prediction due to irregular changes in position
and area of coronal holes.
American Geophysical Union reports on 200 year old sunspot drawings
discovered in Maine: 
Don't miss the Solar Eclipse QSO Party on Monday, August 21 from
1400-2100 UTC.  This is a wide-ranging propagation experiment
intended to observe what happens when the moon blocks ionizing solar
radiation from the ionosphere.  The event is sponsored by ARRL and
HamSCI, and the details are in the August 2017 QST, or you can read
the same QST article at .
Martin McCormick, WB5AGZ of Stillwater, Oklahoma reported on July
"This has been one of the less spectacular sporadic E seasons so far
with several openings but very few that are the type one will
remember much after they occurred.
After learning that WWV had installed a turnstile antenna on its 25
MHZ transmitter, I began parking a receiver on that frequency to see
if I could hear it in North-Central OK.
The first couple of weeks were nothing but then WWV began coming in
around 0000 UTC starting July 20.
Whatever is ionizing the E layer to create this propagation is
sticking around for a few days because once it started fading in, it
has made numerous appearances this last week.  It has mostly been in
the mid to late evenings Central time but on Sunday July 23, it has
been in with a fair signal since around 1200 UTC and is still
somewhat audible at 1700 UTC as I write.
It is good that WWV is transmitting on 25 MHZ as there are almost no
steady identifiable signals in high HF and low VHF anymore to
indicate when the bands are open.
There is an announcement at 17 minutes past the hour stating that
the turnstile antenna's configuration will not change until after
the eclipse on 21 August.
The theory that one of the possible triggers for a Sporadic E event
has to do with clouds of iron and magnesium atoms from meteorites is
interesting because we seem to have nothing for days at a time even
though Geo magnetic activity is not unusually low or high and then
we have several active days of Sporadic E and the numbers are not
any different than they were when there was no E sub S at all."
Today Martin wrote:
"The idea that a cloud of something such as magnesium or iron ions
is one of the factors makes a lot of sense since we don't have
Sporadic E every day, all Summer or all Winter even though the angle
of Solar radiation is totally predictable and the Geo magnetic
activity indices are always present if variable so something else
which is hard to see and slow-moving must also contribute to causing
sporadic E.
Those of us who have been listening to both sporadic E and normal
ionospheric propagation for years notice that the fading rate of
signals always speeds up when there is lots of variation in the
Sun's magnetic field and slows way down when things are quiet.
The 25 MHZ WWV signal was audible here last week almost every
evening and most of last Sunday but this week, there have been only
a few seconds in which it pops in briefly and then everything goes
dead again."
For more information concerning radio propagation, see the ARRL
Technical Information Service at  For an explanation of
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 20 through 26, 2017 were 0, 0, 0, 0, 0, 12,
and 0, with a mean of 1.7.  10.7 cm flux was 70.2, 69.4, 69.5, 70.6,
70.1, 69.8, and 68.6, with a mean of 69.7.  Estimated planetary A
indices were 7, 14, 16, 14, 12, 9, and 11, with a mean of 11.9.
Estimated mid-latitude A indices were 6, 13, 18, 16, 13, 9, and 15,
with a mean of 12.9.


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