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ARRL Propagation Bulletin ARLP050 (2019)

ARLP050 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 50  ARLP050
From Tad Cook, K7RA
Seattle, WA  December 13, 2019
To all radio amateurs 

ARLP050 Propagation de K7RA reports that Wednesday, December 11 was the 28th
consecutive day with zero sunspots. To date in 2019, 77% of days had
no sunspots. Compare this to the previous solar minimum, when 2008
had zero sunspots on 73% of days and 2009 the number of spotless
days stood at 71%.
Average daily solar flux this week (December 5 to 11) was 70.7, up
marginally from the previous week when average flux values were
At the bottom of the solar cycle there is hardly any geomagnetic
activity, with average daily planetary A index at 3.7 and average
middle latitude A index at 1.9. That is very quiet, and is favorable
to propagation on 160 meters.
Just like the report in last week's bulletin, predicted solar flux
is 70 on each of the next 45 days, through January 26.
Predicted planetary A index is 5 on December 13 to 16, then 8, 12,
8, 8 and 10 on December 17 to 21, 5 on December 22 to January 4, 8
on January 5, then 5 on January 6 to 8, then 8 on January 9 and 10,
5 on January 11 to 13, 12 on January 14, 10 on January 15 to 17, and
5 on January 18 to 26.
Geomagnetic activity forecast for the period December 13, 2019 to
January 07, 2020 from F. K. Janda, OK1HH.
"Geomagnetic field will be: 
Quiet on: December 15 to 17, 28-31, January 1 to 4 
Quiet to unsettled on: December 23 to 25 
Quiet to active on: December (13-) 14, 22, January 7 
Unsettled to active on: December 18, 21, (26 and 27,) January 5 
and 6 
Active to Disturbed: (19 and 20)
Solar wind will intensify on: December (13 and 14, 16,) 18 to 21,
(26,) January 7
Parenthesis means lower probability of activity enhancement.
Everything suggests that we are very close to the minimum of the
11-year cycle at present stage of development."
G4KSG reported on December 9 at 0900 UTC hearing a conversation on
20 meter SSB between an EA7 and JA3, with his dipole at 30 feet.
Checking W6ELprop on that date it looks like signals between Spain
and Japan would peak (just barely) around 0730 UTC, but fade by
0900. Between England and Japan signals would be peaking around
0700-0800 UTC, then fading. From Spain to England, signals might be
marginal at 0900, but then improving with the best time from
1030-1400 UTC. So even with no sunspots, propagation still happens.
K6XC reported on December 9, 10 meters appeared dead, but at 2020
UTC he worked ZL1SW using FT8.  He used a hexbeam at 40 feet pointed
at 60 degrees. Short path to ZL1SW from K6XC is 226.7 degrees, and
long path is 46.7 degrees.
Two recent articles from Nature on the Parker Solar Probe:
The ARRL 10 Meter Contest is this weekend, starting Friday night in
North America. Check
Although we are currently at solar minimum, conditions may be
enhanced by the Geminids meteor shower. Monitoring suggests a fair amount of activity.
Check this for more information on how this service works:
Check this out. A new prediction for the end of cycle 24 and new
cycle 25:
K8MKN wrote:
"Here's a suggestion, especially with all these zero reports of
sunspots. Can you do a flashback to what the Sunspot readings were a
year ago or two years ago or maybe 11 years ago? It might be
interesting to put it in context with what's going on today."
Here are the bulletins from 2013-2018, with sunspot numbers toward
the bottom:
They show average daily sunspot numbers (working backwards) of 9.7,
2.3, 40.9, 48, 88.4, and 102.9.
The latest from WX6SWW:
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 and 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 December 5 through 11, 2019 were 0, 0, 0, 0, 0,
0, and 0, with a mean of 0. 10.7 cm flux was 70.7, 70.3, 70.2, 71.6,
70.7, 70.6, and 70.7, with a mean of 70.7. Estimated planetary A
indices were 3, 4, 2, 3, 4, 4, and 6, with a mean of 3.7. Middle
latitude A index was 1, 2, 1, 2, 2, 2, and 3, with a mean of 1.9.


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