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ARRL Propagation Bulletin ARLP049 (2017)

ARLP049 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 49  ARLP049
From Tad Cook, K7RA
Seattle, WA  December 15, 2017
To all radio amateurs 

ARLP049 Propagation de K7RA

Over the past reporting week (December 7-13) we saw three days with
zero sunspots (December 8, 9 and 13). Compared to the previous seven
days, average daily sunspot number more than doubled to 6.9 and
average daily solar flux increased from 69.6 to 71.

One new sunspot group (2691) emerged on December 10 with one spot,
which increased to three over the next two days, but by December 13
it had all disappeared. You can see it at, .

According to as of Thursday, December 14, for all
of 2017 so far 27% of all days have had no visible sunspots.  They
say the blank Sun count for 2016 was 9%. They show the count for
2009 at 71%.

Current sunspot and solar flux numbers are low enough that coverage
for local 75 and 80 meter nets suffers, because they are too low to
reflect back high angle radiation at 3.5-4 MHz.

Geomagnetic numbers were low, with average planetary A index
declining from 11.6 to 7.4, and mid-latitude A index from 8.1 to

The latest forecast from USAF and NOAA shows solar flux at 72 on
December 15-17, 75 on December 18-21, 74 on December 22-23, 72 on
December 24-26, 70 on December 27 through January 5, 72 on January
6-8, 74 on January 9-19, 72 on January 20-22, and 70 on January

Predicted planetary A index is 5 on December 15-16, then 12, 20, 18,
10 and 8 on December 17-21, 5 on December 22-26, 12 and 8 on
December 27-28, 5 on December 29-30, then 10, 26, 14 and 10 on
December 31 through January 3, 5 on January 4-6, then 14, 16, 14 and
8 on January 7-10, 5 on January 11-12, then 8, 25, 10, 8 and 8 on
January 13-17, 5 on January 18-22, then 12 and 8 on January 23-24, 5
on January 25-26 and 10 and 26 on January 27-28.

The above predictions are updated daily, usually after 2115-2130z,
and are located at, .

F.K. Janda, OK1HH sent his geomagnetic activity forecast for the
period December 15 to January 10, 2017:

"Geomagnetic field will be:
Quiet on December 23-24, 26, January 5-6,
Mostly quiet on December 16, 25, January 4,
Quiet to unsettled on December 15, 17, 30, January 7-8
Quiet to active on December 20-22, 27-29, 31, January 3, 9
Active to disturbed on December 18-19, January 1-2, 10

"Amplifications of the solar wind from coronal holes are expected on
December (17,) 18-22, (24-25, 30-31,) January 1-3, (4,) 5-7, (8)

"Parenthesis means lower probability of activity enhancement."

A pretty good post about aurora appeared in an adult Scouting blog
at, .
It showed nice images of aurora too, although it is important to
keep in mind that the most beautiful and dramatic images are
captured using long exposure times.

This post makes a common error when it says, "The Sun cycles in
about 11 years of increased sunspots," when actually the period of
increased sunspots is somewhere in the middle of this period. Eleven
years is the approximate total length of a typical solar cycle,
which may vary from 9 to 14 years, from one solar minimum to the

English usage nitpick: Instead of "and can hurdle solar particles
toward Earth," I think the word the author had in mind was "hurtle."
They sound mostly the same, so are often confused, according to

The post contains a very useful link to a frequently updated
forecast of aurora at, .

Reports from last weekend's ARRL 10-Meter Contest indicate terrible
conditions. I operated briefly on Saturday, hearing nothing but
local area CW signals, no phone.

Checking the ARRL contest soapbox at, indicates nobody used a dupe
sheet or duplicate checking program because activity was so low,
they didn't need one.

KE2SX in North Carolina (FM05sw) commented that he worked only 6
"very local stations" over the whole weekend, all in his state so
there was only a single multiplier, his own state.

K2AF reported from New Jersey (FN20nu) that this is his favorite
contest, but "This year, I am hoping that I got both station's calls
right so that I don't end up with a negative score."

The latest space weather news from Dr. Tamitha Skov:

FT8 (the latest mode from K1JT) seems to have taken the amateur
radio service by storm in recent months, with an amazing rate of
acceptance due to its weak signal capabilities and easy

But check out this blog post from NW7US regarding the Olivia mode,
which facilitates actual conversations via weak signals:

NW7US is a propagation expert who among other things writes and
edits the monthly CQ Magazine Propagation column.

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
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 7-13, 2017 were 11, 0, 0, 11, 13, 13,
and 0, with a mean of 6.9. 10.7 cm flux was 67.9, 69.9, 71.1, 72,
72.3, 71.4, and 72.1, with a mean of 71. Estimated planetary A
indices were 10, 5, 4, 3, 10, 13, and 7, with a mean of 7.4.
Estimated mid-latitude A indices were 9, 4, 3, 2, 8, 9, and 4, with
a mean of 5.6.


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