Register Account

Login Help

ARRL Propagation Bulletin ARLP020 (2021)

ARLP020 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 20  ARLP020
From Tad Cook, K7RA
Seattle, WA  May 14, 2021
To all radio amateurs 

ARLP020 Propagation de K7RA

Sunspot activity returned last Friday, and has held steady since.
Average daily sunspot numbers rose from 11.9 to 21.1, and average
daily solar flux was up 2.1 points to 74.3 for the reporting week
ending May 12.

Geomagnetic activity was quiet until Wednesday when the planetary A
index went to 41, as the result of a CME that blasted out of the Sun
on May 9. It was not expected to be very strong, but when it struck
on May 12 it sparked a G3 class geomagnetic storm, the strongest in
the current solar cycle.

The planetary A index rose to 41, far above an average of 3.8 on the
previous six days. The average daily planetary A index for the week
(May 6-12) was 9.1 and average middle-latitude A index was 7.4.

Predicted solar flux over the next month is 75 on May 14-19, 70 on
May 20-21, then 72, 80, and 79 on May 22-24, then 78, 77 and 73 on
May 25-27, 72 on May 28-30, 70 on May 31 and June 1, 71 and 75 on
June 2-3, 76 on June 4-5, 74 on June 6-7, 75 on June 8-9, 77 on June
10, and 79 on June 11-13.

Note in the 45-day forecast that solar flux of 84 predicted for June
15 seems to be an outlier:

Odd that predicted solar flux would shift from 78 to 84 to 77. But
we saw a similar prediction recently for that same value a week into
the future, but any trace of it here seems to have disappeared down
the memory hole:

There seems to be some problem accessing FTP (File Transfer
Protocol) lately on some web browsers. It gradually disappeared from
Microsoft Edge, then Firefox, then Chrome. I discovered that
although I keep the Windows OS updated, the old Internet Explorer
still exists on my PC, and it does not block FTP.

Predicted planetary A index is 5 on May 14-16, then 15, 12, 8, 5 and
8 on May 17-21, 5 on May 22 through June 5, then 8, 5 and 8 on June
6-8, then 8, 5, 12, 18, and 15 and on June 9-13.

Geomagnetic activity forecast for the period May 14 to June 8, 2021
from F.K. Janda, OK1HH of the Czech Propagation Interested Group,
compiling this geomagnetic activity weekly forecasts since January

"Geomagnetic field will be:
quiet on: May 19, 25-26, (27-31)
quiet to unsettled on: May 21, 24, 31, June 1-8
quiet to active on: May (14-16, 18, 20-23)
unsettled to active: May (17)
active to disturbed: none
"Solar wind will intensify on: May (16,) 17-18, (21-25,) 28-30."
- Parenthesis means lower probability of activity enhancement.
- Contradictory indications significantly reduce the accuracy of the

Jon Jones, N0JK EM28 Kansas wrote: "6m Es to W6 May 14 to Silicon
Valley. Worked AH0U and N5KO both CM97. They are in the sporadic-E
'doughnut' between single and double hop Es."

Ken Brown, N4SO checks this graph of the EISN each day and "compares
it with propagation on 30 and 17 meters. Of interest are stations in
China, Japan, Korea, and Asiatic Russia propagated at 6000 miles

The estimated international sunspot number (EISN) is a daily value
obtained by a simple average over available sunspot counts from 85
worldwide observers in the SILSO network.

Also see:

Ken also reported:

"W1AW Schedule on CW, 18.0975 MHz,  7 PM Code Bulletin, May 11, W1AW
signals are 40 dB over S9, so I called CQ QRP.

"Power set to all the way down on the Elecraft K2. Low setting reads
.1 and W1 power meter reads the lowest power at 100 mW. 0049 UTC
QRPp 18.076 MHz 100 mW.

"W3UA  N4SO/QRP   18076.1 CW CQ  16 dB  22 wpm  0048z 11 May 
KM3T  N4SO/QRP   18076.0 CW CQ  4 dB   22 wpm  0047z 11 May

"and at 0126 UTC K7QO 18.077 MHz  3 watts QRP.

"May 11, FT8 mode, 10.136 MHz.

"Long string of Japanese worked starting with a CQ from JA6VZ at
0745 UTC.

"Stations worked/confirmed at 0931 UTC with JE1VTZ and extends to
1114 UTC with JA2KVD, and JM1FHL with over 26 worked.

"Strongest stations were JE0ART at -3 dB and JA1IOA at +5 dB.  Both
of these are very strong and rare for a roughly 7000 mile path.

"Several times (1011 UTC and 1028 UTC) the Band Activity was listing
a complete string of Japanese call signs busy with a contact or
calling CQ. My activity screen will list about 24 call signs.

"The Reverse Beacon Network.

"At the same time period I checked RBN 10 meters and found this for
the very early time of 1043 UTC.

"KC0VKN  K4SE  28038.2 CW CQ  1 dB   7 wpm  1043z 11 May

"Locations are Tennessee (K4SE) and Oxford, Iowa. (KC0VKN)"

Thanks to the the ARRL Contest Update for the following:

Check this link for a reference on sporadic-E propagation:


Then check this for an interesting sporadic-E real time online tool:

Two recent reports from the Space Weather Woman, Dr. Tamitha Skov,

If you would like to make a comment or have a tip for our readers,
please email the author at, .

For more information concerning shortwave radio propagation, see and the ARRL Technical Information
Service web page 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

Instructions for starting or ending email distribution of ARRL
bulletins are at .

Sunspot numbers for May 6 through 12, 2021 were 0, 15, 17, 18, 36,
31 and 31, with a mean of 21.1. 10.7 cm flux was 70.8, 74.5, 71.6,
75.9, 76.5, 76.1, and 74.7, with a mean of 74.3. Estimated planetary
A indices were 4, 3, 3, 4, 6, 3, and 41, with a mean of 9.1. Middle
latitude A index was 2, 3, 4, 6, 8, 4, and 25, with a mean of 7.4.


Instragram     Facebook     Twitter     YouTube     LinkedIn