Propagation Forecast Bulletin 52, 29 Dec 2018

Accessed on 29 December 2018,1652 UTC, Post 818.


Email message from W1AW and HQ ARRL, Newington, CT, 06111.

Here’s the latest propagation forecast from Tad Cook (K7RA) and his volunteer staff of observers and reporters. Views expressed in this bulletin are those of Mr. Cook and his contributors.

Propagation Forecast Bulletin 52  ARLP052
From Tad Cook, K7RA
Seattle, WA  December 28, 2018
To all radio amateurs

ARLP052 Propagation de K7RA

No sunspots over our reporting week, December 20-26, so compared to
the previous seven days average daily sunspot number declined from
3.4 to 0.

Average daily solar flux was 70, down slightly from 70.4.

Average planetary A index increased from 4.1 to 4.3, while average
mid-latitude values went from 3 to 4.

Predicted solar flux is 69 on December 28 through January 4, 72 on
January 5, 70 on January 6-13, 69 on January 14 through 18, 71 on
January 19-26, 72 on January 27 through February 1, 70 on February
2-9, and 69 on February 10.

Predicted planetary A index is 8, 12, 8, 12 and 10 on December 28
through January 1, 5 on January 2-4, then 10, 10 and 8 on January
5-7, 5 on January 8-12, 8 on January 13, then 5, 5 and 12 on January
14-16, 5 on January 17-19, 8 on January 20, 5 on January 21-23, then
8, 12, 10 and 8 on January 24-27, 5 on January 28-29, 10 and 12 on
January 30-31, 10 on February 1-2, 8 on February 3, and 5 on
February 4-10.

Geomagnetic activity forecast for the period December 28, 2018 to
January 23, 2019 from F.K. Janda, OK1HH.

“Geomagnetic field will be:
Quiet on January 10-12, 22-23
Quiet to unsettled on January 13, 19
Quiet to active on December 28, 31, January 1-2, 9, 20
Unsettled to active on December 29, (30,) January (3-5,) 6-8, 14, 17-18, 21
Active to disturbed on January (15-16)

“Solar wind will intensify on December 28-31, January 1, (3-4,) 5-7,
(8, 13-14,) 15-16, (17-19)

“Parenthesis means lower probability of activity enhancement.”

Al Brown, W1VTP of Manchester, New Hampshire sent this email:

“I manage The Vermont Net on 3975 kHz at 2330 UTC. We have been
having propagation issues since November. I recall similar
difficulties back in 2009 and it straightened out somewhere around
mid Feb 2010. I have used the foF2 map (see put out by the Australian
government for some time but it doesn’t always make sense. I
understand that amateur radio operators are mostly interested in DX
(make that ‘long haul’) propagation. But some of us have regional
nets with average distance of 100 miles.

“Do you have any other explanation where I could predict propagation
for a given night? I’m thinking it may have something to do with a
disturbance in the magnetosphere and the effect of coronal dark
holes when pointed at earth but do not have any reference material
to back that up.

“The closest thing I have is that foF2 map but it doesn’t always
work out that way.”

We covered the same issue in this bulletin in the past, but I can’t
locate the bulletin. This happens when sunspot numbers are too low
to support local propagation on 75-80 meters. We might think of
local nets in that part of the spectrum using groundwave
propagation, but for wider coverage beyond line-of-sight it depends
on high angle signals reflecting back from the ionosphere.

This is why NVIS antennas are useful (see ).

When I asked K9LA about this, Carl responded, “The MUF can be low
enough that high angle 75m/80m signals go thru the ionosphere at
night during the winter (especially at solar minimum). As you know,
with high angle signals, the MUF is pretty close to foF2 – so foF2
could be a good indicator. You may have to modify foF2 a bit based
on distance. And having an ionosonde near you would be best.”

Here is a site with a number of links to ionosondes:

Note the link to Millstone Hill, which may be the closest ionosonde
to W1VTP.

Click on the MHJ45 link.

Clicking on that link goes to a page with ionosonde data from 1992
to 2018.

If you click on 2018, it will take you to links for all 12 months of
the year. Click on December, and click on the latest date, and you
will see links for every 15 minutes of the day. I clicked on the
latest one, which was for 0930 UTC at the time. It showed the foF2
value at 2.45 MHz, which is too low to support local high angle
coverage for 75 meters, but 160 meters should work.

I see there are links to ionosondes at Wallops Island (Virginia),
Boulder (Colorado), Eglin AFB (Florida), Idaho National Labs and
many other locations around the globe.

K9LA suggested that the net could QSY to 160 meters when this

The ionogram I am looking at currently can be seen here:

You see MHz on the X-axis and timing on the Y-axis. A chirp signal
is swept across the HF spectrum, and the wispy looking echoes are
what comes back. The various timings reveal the elevation of ionized

This tool should help to get a handle on this propagation problem.

From 0000-2359 UTC on January 1, is the annual ARRL Straight Key
Night operating event:

Dr. Tamitha Skov put out this video shortly after Propagation
Forecast Bulletin ARLP051 was released last week, so this is a
little out of date:

You can check here for her more recent dispatches:

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 20 through 26, 2018 were 0, 0, 0, 0, 0,
0, and 0, with a mean of 0. 10.7 cm flux was 69.8, 71.1, 71, 70.2,
69.5, 69.6, and 68.7, with a mean of 70. Estimated planetary A
indices were 12, 5, 3, 3, 4, 4, and 3, with a mean of 4.9. Estimated
mid-latitude A indices were 9, 4, 3, 3, 3, 4, and 2, with a mean of

Attachments area
Preview YouTube video A Bit of a Mixed Bag: Solar Storm Shortie 12-20-2018