SWL PROPAGATION
February 2014
High-frequency
Propagation This Month
Sunspot
Cycle 24 has been quite tame compared with recent cycles. Some are speculating that we’ve already seen
the peak of this cycle—but time will tell.
How alive can the higher frequencies be with long-distance
propagation? It is always a surprise to
the casual Amateur Radio Operator and SWLer when they get on a band like ten
meters during the solar minimum, and discover that there is still some life on
the band, beyond Short-Skip distances. This
can be especially true during periods when massive sunspots occur and raise the
daily 10.7-cm flux levels enough to wake up the higher frequencies. However, the low solar activity of recent
months just does not support world-wide Dxing on the highest HF bands for any
significant length of days. The lower HF
bands can become real players, though, as veteran HF operators know.
We
are starting to approach the end of the winter season. The period of darkness is growing shorter,
causing a rise of the average daily maximum usable frequency (MUF) on any given
radio propagation path that traverses the ionosphere in the Northern
Hemisphere. That’s helpful in overcoming
the increasing geomagnetic activity expected. Additionally, noise levels are still
low, so reliable DX is possible. The
solar activity is finally high enough to provide HF ionospheric propagation on
higher frequencies (even some low-VHF F-region propagation has been observed
since late 2011). General conditions are
expected to be good to excellent for HF propagation throughout February.
Specifically,
during the first three months of the year the earth is at perigee with the
sun. This causes long winter nights,
which in turn allows the ions of lower layers to drift upward and add to the F2
region. The F2 region contains the
maximum ion density (foF2), which usually defines the maximum usable frequency
(MUF) for DX paths.
Throughout
these winter months, the foF2 increases slowly day-by-day until it reaches the
highest monthly average of the year sometime during this quarter.
On
the shortwave bands above 22 meters, expect paths to open shortly after
sunrise, and will remain open until early to late evening. Morning and evening DX openings between some
areas in the Northern Hemisphere on these bands are very short, because the
band in question closes on one end of the path before it opens on the opposite
end.
Paths
on 31 through 22 meters remain in their seasonal peak much like in January, but
with longer openings. Continue to look
for great openings between North America and Europe in the morning and between
North America and Asia during the late afternoon hours. Twenty-two meters will
often be the best daytime DX band, with 31 and 25 running a close second.
Ninety
through 41 meters will be useful almost 24 hours a day. Daytime conditions will resemble those of 25
meters, but skip and signal strength may decrease during midday on days with
high solar flux values. Nighttime will
be good except after days of very high MUF conditions. Generally, the usable distance is expected to
be somewhat greater on the higher of these bands than on 90. DX activity tends to increase later in the
evening toward midnight. Look for Africa
and South Pacific (Australia, Papua New Guinea, and so on) on 90 through 60
meters throughout the night. On 41, 49
and 60 meters, long path DX is possible along the gray line.
The
120-meter band continues to remain stable, with very low noise levels. Throughout the winter season, high noise may
occur during regional snowstorms. The
band opens just before sunset and lasts until the sun comes up on the path of
interest. Except for daytime short-skip
signal strengths, high solar activity has little impact. Continue to look for Europe and Africa around
sunset until the middle of the night, and then Asia, the Pacific, and the South
Pacific as morning approaches.
Signals
below 120 meters will remain strong and exciting, except during times of
regional storms and high geomagnetic activity.
Medium Wave DX is still quite hot throughout February.
VHF Conditions
Trans-equatorial (TE) scatter propagation
tends to increase during the equinoctial period and some 6-meter openings may
be possible between 7 and 10 PM local time.
The best bet for such openings is between the southern tier states and
South America for paths approximately at right angles to the equator. An occasional TE opening may also be possible
on 2 meters. Unlike F2-layer or
sporadic-E openings on 6 meters, TE openings are characterized by very weak
signals with considerable flutter fading.
If you use Twitter.com – you can follow
@hfradiospacewx for hourly updates that include the K index numbers (and,
follow this columnist – @nw7us). You can
also check the numbers at < http://SunSpotWatch.com >.
CURRENT
SOLAR CYCLE PROGRESS
The Royal
Observatory of Belgium, the world’s official keeper of sunspot records, reports
a monthly mean sunspot number of 90.3 for December, 2013, up from November’s
77.6 and from October’s 85.6. The low
for the month was 65 on December 7. The
high of 136 occurred on December 10. The
mean value for December results in a 12-month running smoothed sunspot number
of 62.6 centered on June 2013. Following
the curve of the 13-month running smoothed values, a smoothed sunspot level of 79
is expected for February 2014, plus or minus 14 points.
Canada's Dominion
Radio Astrophysical Observatory at Penticton, British Columbia reports a
10.7-cm observed monthly mean solar flux of 147.7 for December, 2013, about the
same as November’s 148.4. This indicates
a clear resurgence of solar activity.
This provided a lot of great DX and activity even on the Ten-meter band. The twelve-month smoothed 10.7-cm flux
centered on June 2013 is 120.9, up from May’s 118.1. A smoothed 10.7-cm solar flux of about 134 is
predicted for February 2014.
The geomagnetic
activity as measured by the planetary-A index (Ap) for December 2013
is 5. The twelve-month smoothed Ap index centered on June 2013 is a
steady 7.1. Geomagnetic activity should be much the same as we have had during January.
Refer to the Last Minute Forecast for
the outlook on what days that this might occur (remember that you can get an
up-to-the-day Last Minute Forecast at < http://SunSpotWatch.com > on the
main page).
I'd like to hear
from you
I welcome your
thoughts, questions, and experiences regarding this fascinating science of
propagation. You may e-mail me, write me
a letter, or catch me on the HF Amateur bands.
On Twitter, please follow @NW7US (and if you wish to have an hourly automated
update on space weather conditions and other radio propagation-related updates,
follow @hfradiospacewx). I invite you to
visit my online propagation resource at < http://sunspotwatch.com/ >,
where you can get the latest space data, forecasts, and more, all in an
organized manner. If
you are on Facebook, check out < http://www.facebook.com/spacewx.hfradio
> and < http://www.facebook.com/NW7US >.
Until next month,
73, Tomas, NW7US
PO Box 27654
Omaha, NE 68127
@NW7US
@hfradiospacewx
No comments:
Post a Comment