ARRL

ARRL Propagation Bulletin ARLP013 (2008)

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 20, 2008
To all radio amateurs 

SB PROP ARL ARLP013
ARLP013 Propagation de K7RA

ARRL Headquarters is closed for Good Friday on March 21, so this
bulletin is coming out a day early, and on the Vernal Equinox.

We had a few more days with visible sunspots over the past week.
Sunspot numbers on March 15-17 were 12, 12 and 11.  Over the past
month we seem to have a single sunspot appear for a few days, then
fade away or rotate out of view, then another pop up after four or
five days.  Take a look at sunspot numbers since January 1 at,
http://www.swpc.noaa.gov/ftpdir/indices/quar_DSD.txt.

Dale Drake, W7GMY of Lake Helen, Florida asks, "Just a curious
question on the cycle numbers.  How do they come up with cycle
numbers?  Cycle 24 would indicate at 11 years per cycle that it is
253 years in recording the cycles."

Dale was surprised to learn that daily sunspot records do stretch
way back over hundreds of years, and Cycle 1 in fact peaked a
quarter century prior to America's Revolutionary War.  Check the
WM7D web site at, http://wm7d.net/hamradio/solar/historical.shtml to
see graphs of Cycles 1-23.

Paul Kiesel, K7CW of Tahuya, Washington sent a fascinating article
translated from the September 2006 issue of Japanese radio magazine
CQ Ham Radio.  JE1BMJ wrote about surprising long distance 6-meter
polar propagation from Japan to Europe with sporadic-E at the summer
solstice.  He doubts this is multi-hop propagation, even though the
long distance suggests this, because the signals don't seem to be as
dispersed or scattered as one would expect from multiple hops.

Instead, JE1BMJ posits that the mechanism is PMSE, or Polar
Mesosphere Summer Echo, a radar echo phenomenon.  Rather than taking
several hops, the signal would be refracted through the E-layer for
a long distance following the curvature of the earth, before exiting
and being heard in Europe.

There was a great deal of mail this week on possible auroral-E
propagation in the summer on 6 meters, when the K index is high and
there is backscatter via aurora.  But while the normal auroral
communications sound distorted, E-layer propagation will arise which
is not at all distorted.

K7CW reports an opening from the Pacific Northwest on 6 meters to W4
and W5 on October 20, 2007.  There was aurora, but at the same time
this propagation over long distance that did not seem to be via
aurora, sounding very strong and clear.  K7CW wonders if this might
be an example of Snell's Law, which addresses refraction along an
interface between two mediums.

Ray Perrin, VE3FN of Ottawa, Ontario wrote about possible auroral-E
propagation while operating from the arctic in Iqaluit, on Baffin
Island at Frobisher Bay in Nunavut at 63.75 degrees north latitude,
68.52 degrees west longitude.  Ray made several business trips there
in 1999-2002. Iqaluit is where the VE8BY 6 meter beacon is located,
in grid square FP53.

For 6 meters Ray used a wire dipole tied to a rock thrown from his
bedroom window in his temporary housing, and another dipole made
from two telescoping antennas mounted on his porch.

Ray writes, "I worked many stations in North America using these
simple antennas.  For example, during 2 weeks in July and August of
2001, I worked into VO1, VE1, VE2, VE3, W1, W2, W3 and W4 as far
south as NC.  I also worked some in W8 and W9 and one station in
Colorado.  There didn't appear to be a distinct skip zone.  And
about 40% of the evenings, I heard the OX3SIX beacon (on 50.012 MHz
or so) for about 45 minutes at 0000Z.  It would roll in on auroral E
-- no distortion.  I always called CQ when I heard the beacon, but
no QSOs.  I later received a report from a station in northern
Scotland saying he thought he had heard me.  It is likely he did as
I was calling CQ at the time.  Again, this was all auroral E -- no
'buzz'.  In Feb 2002, I worked SP2NA on F layer using the wire
dipole."

Ray's last trip to Iqaluit was November 2002.  He used a 2-element
Yagi for 6 meters.  He says, "During that trip I worked OX3SA on
auroral E.  Later, I also worked into VE6 (DO33) on auroral E.  BTW,
the evening I worked VE6 (a Saturday), I was hearing beacons in VE6,
VE4 and northern W0 for about 3 hours, but I was only able to dig up
one QSO!  I was simultaneously calling CQ on 144 MHz, but nothing
heard.  At noon the next day (Sunday) the band opened briefly on F
layer to southern Florida -- about 3000 miles."

Ray continues, "Except for a few QSOs on F-layer, all my contacts
appear to have been on auroral E.  The signals were not distorted as
they would have been on straight aurora.  I would typically wait for
a day when the K index went up to 5 and the band would often open in
the evening -- especially in the summer. I have heard the VE8BY
beacon many times from Ottawa on auroral E, but never when the band
was open on 'buzz' aurora.  And when we do have 'buzz' auroral
signals coming in on 6 meters, I have never heard VE8BY/b."

Ray goes on to say, "So what is the cause of auroral E?  Is there
any relationship to the occurrence of auroral E and the sunspot
cycle?  Some have suggested that auroral E may occur when the aurora
becomes weaker.  If this were so, then one would expect to hear
auroral E on, say, 50 MHz when there is 'buzz' aurora on 28 MHz.  In
other words, as the MUF rises, one would first experience auroral E
and then straight 'buzz' aurora.  But if this were true, one would
expect to hear auroral E frequently on 50 MHz (at mid latitudes)
when, in fact, I believe it is quite rare at mid latitudes.  And one
would expect to observe auroral E quite frequently on 144 MHz when
50 MHz is open on 'buzz' aurora, but it isn't intense enough to
propagate 'buzz' aurora on 144 MHz.  Once again, this doesn't wash
as auroral E on 144 MHz seems to be very rare at mid latitudes.  I
once thought that ordinary 'buzz' aurora was related to paths that
were more or less east - west whereas my QSOs from FP53 (auroral E)
were predominantly north - south.  However, my QSO with OX3SA and
frequent reception of the OX beacon involve east - west paths -- and
they were all auroral E."

K9LA sent a lot of great material about auroral E propagation, but
there isn't room to address it in this bulletin.

But go to Carl's web site at,
http://mysite.verizon.net/k9la/id4.html and click on the titles
"Alaska to EU on 6m," "More Alaska to EU on 6m" and "Summer 6m Es
Probabilities" to download PDF documents he wrote for his
propagation column in World Radio.

Also, K7CW recommends for 6 meters http://dxworld.com/50prop.html
and the UK Six Meter Group at, http://www.uksmg.org/index_cs.php.
Also check out a revised article from NASA last week on solar cycle
prediction at http://solarscience.msfc.nasa.gov/predict.shtml.

Finally, no room to talk about a very important development for HF
propagation, the first day of Spring, which is today.  This is a
great time for worldwide HF propagation, as all of the earth is
receiving a maximum amount of solar radiation, the same in both
southern and northern hemispheres.

Projection for the near term is a planetary A index of 5 for March
20-24, then 10, 20, 25, 20 and 8 for March 25-29.  There are similar
returns to a planetary A index of 25 predicted for April 5, April 23
and May 2, but otherwise quiet.

Geophysical Institute Prague predicts quiet to unsettled conditions
for March 21, quiet March 22-24, unsettled March 25, and active
March 26-27.

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://www.arrl.org/tis/info/propagation.html.  For a detailed
explanation of the numbers used in this bulletin, see
http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
propagation bulletins is at http://www.arrl.org/w1aw/prop/.  Monthly
propagation charts between four USA regions and twelve overseas
locations are at http://www.arrl.org/qst/propcharts/.

Sunspot numbers for March 13 through 19 were 0, 0, 12, 12, 11, 0,
and 0 with a mean of 5.  10.7 cm flux was 69.5, 69.9, 69.5, 70.3,
69.8, 69.6, and 69 with a mean of 69.7.  Estimated planetary A
indices were 14, 13, 11, 5, 4, 8 and 6 with a mean of 8.7.
Estimated mid-latitude A indices were 11, 12, 7, 4, 3, 7 and 5, with
a mean of 7.
NNNN
/EX