SB PROP @ ARL $ARLP013
ARLP013 Propagation de K7RA

ZCZC AP13
QST de W1AW
Propagation Forecast Bulletin 13  ARLP013
> From Tad Cook, K7RA
Seattle, WA  March 28, 2016
To all radio amateurs

SB PROP ARL ARLP013
ARLP013 Propagation de K7RA

All of the indicators we track were lower over the past week (March 17-23),
compared to the previous seven days. Average daily sunspot numbers declined
from 51.7 to 28.4, and average daily solar flux was 88.8, compared to 98.6
during the prior seven days. Planetary A index was lower by 3.8 points to
11.9, and average mid-latitude A index (measured in Wallops Island, Virginia)
was down from 12 to 8.6. Lower geomagnetic indices are generally considered a
good thing for HF propagation.

Looking at the record at ftp://ftp.swpc.noaa.gov/pub/indices/DSD.txt we can
see that until March 24, there were no new sunspot regions since March 17 when
there was one, which followed two on the day before.

Even though our Sun is quiet, there is a seasonal variation which produces
aurora around the Vernal and Autumnal Equinox. (Vernal, or Spring Equinox was
on Sunday, March 20, 2016 and the next Autumnal or Fall Equinox this year will
occur on Thursday, September 22, 2016.)

Spaceweather.com supplied this article a few days ago explaining how this
works:

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/40/ .

> From NOAA and the USAF, predicted solar flux is 88, 90, 92 and 88 on
> March 25-28, 90 on March 29 through April 3, 95 on April 4-11, 90 on
> April 12-17 and 85 on April 18-20. Flux values are predicted to go back
> to 95 again after April 30.

Also via NOAA, planetary A index for March 25-29 is predicted at 5, 8, 8, 10
and 8, then 5 on March 30 through April 1, then 30, 20 and 8 on April 2-4, 5
on April 5-7, then 10, 5, 15, 24, 22, and 20 on April 8-13, and 8 on April
14-15. The A index then jumps to 30 on April 29.

F.K. Janda, OK1HH sends us his geomagnetic forecast, but this week I want to
test a different format. You can see the format we've been using in past
bulletins at http://arrl.org/w1aw-bulletins-archive-propagation. See below for
a link to my survey.

Here is the proposed format:

Geomagnetic activity forecast for the period March 25-April 20, 2016

Geomagnetic field will be:
Quiet on March 25-26, April 1, 14, 17-18
Mostly quiet on March 30-31, April 6, 10, 15-16, 19
Quiet to unsettled on March 27, 29, April 7, 20
Quiet to active on March 28, April 5, 8-9, 11, 13
Active to disturbed on April 2-4, 12

Increases in solar wind are expected on March (30), April 4-6, 9, 11, 14

Remarks: - Parenthesis means lower probability of activity enhancement.

See examples and vote at, https://www.surveymonkey.com/r/BP9FMTZ .

Ray Soifer, W2RS in Green Valley, Arizona on March 24 sent this info about
working 30 meter grayline propagation yesterday morning:

"Interesting propagation. I heard nothing from VK0EK until half an hour before
sunrise. He peaked 579 around sunrise, then faded and was gone 30-40 minutes
after. Quite a grayline."

Ray didn't tell me that VK0EK is on Heard Island, but maybe I should already
know that:

http://vk0ek.org/

The distance from Ray's QTH to Heard Island is 10,945 miles, short path.

More info about Heard Island, from the Australian government:

http://heardisland.antarctica.gov.au/

Max White, M0VNG, and earlier David Moore sent this link to an ultraviolet
image of our Sun: http://bit.ly/1RqC0Ar .

Martin McCormick, WB5AGZ of Stillwater, Oklahoma sent this piece in a message
titled "Is it F2, or E?"

"One of the first things a person notices when listening to HF signals coming
from afar is a characteristic sound as if someone was continuously playing
with tone controls. It is especially noticeable on AM signals and the wider
the receiver passband, the more pronounced is the effect. This is known as
selective fading because different frequencies fade in and out at different
times.

"The Earth's ionosphere is a shell or several shells of electrically-charged
air molecules and atoms ranging from around 38 miles above us to about 310
miles high. The Sun and cosmic rays cause the molecules and atoms to loose
electrons which gives them a positive charge. They can reflect radio signals
and give us world-wide radio communication.

"The reflecting layers are the E layer at about 56-93 miles plus the F layer
complex which consists of several shells or layers that come, go and move
around based on Solar and Geo magnetic activity.

"The f2 layer is mostly responsible for short wave communications and the
selective fading is due to more than one layer reflecting the same signal back
to Earth. If the layers happen to be half of a wavelength apart, one receives
two versions of the same signal in which one version is delayed enough to
cause the carrier of an AM or FM signal to be cancelled out. Mother Nature
just turned a normal AM signal in to a double-sideband suppressed carrier
transmission.

"FM signals are also altered. It is possible to receive FM on an AM receiver
by tuning slightly off from center. It is called slope detection and has
existed for as long as there has been FM. If you tune right on to the
frequency, the audio is faint and muffled. F2 propagation, however, can cause
a selective fade just below or above the carrier frequency such that if you
are on the center frequency, the amplitude of the signal matches the deviation
and you can hear fairly good audio as if the signal was both AM and FM. Nature
automatically did that, also but the effect may not last more than a fraction
of a second.

"When sporadic-E is involved, signals still fade up and down but the E layer
acts like a single thin film and there is no selective fading. Except for
fades, signals sound local."

If you would like to make a comment or have a tip for our readers, email the
author at k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL Technical
Information Service web page at, http://arrl.org/propagation-of-rf-signals.
For an explanation of the numbers used in this bulletin, see htt
://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past propagation
bulletins is at http://arrl.org/w1aw-bulletins-archive-propagation. More good
information and tutorials on propagation are at http://k9la.us/.

My own archives of the NOAA/USAF daily 45 day forecast for solar flux and
planetary A index are in downloadable spreadsheet format at http
//bit.ly/1VOqf9B and http://bit.ly/1DcpaC5 .

Click on "Download this file" to download the archive, and ignore the security
warning about file format. Pop-up blockers may suppress the download.

Monthly propagation charts between four USA regions and twelve overseas
locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL bulletins are
at http://arrl.org/bulletins.

Sunspot numbers for March 17 through 23 were 66, 29, 26, 26, 25, 13, and 14,
with a mean of 28.4. 10.7 cm flux was 91.6, 90.3, 89.4, 87.6, 88.9, 87.3, and
86.8, with a mean of 88.8. Estimated planetary A indices were 21, 8, 18, 10,
8, 8, and 10, with a mean of 11.9. Estimated mid-latitude A indices were 16,
6, 12, 6, 7, 6, and 7, with a mean of 8.6.

NNNN
/EX

)\/(ark

Always Mount a Scratch Monkey

... The real world is no place for artists.
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