ARRL

ARRL Propagation Bulletin ARLP052 (2008)

SB PROP @ ARL $ARLP052
ARLP052 Propagation de K7RA

ZCZC AP52
QST de W1AW  
Propagation Forecast Bulletin 52  ARLP052
From Tad Cook, K7RA
Seattle, WA  December 12, 2008
To all radio amateurs 

SB PROP ARL ARLP052
ARLP052 Propagation de K7RA

Finally this week a sunspot group appeared, and this time there was
about three weeks since the last group disappeared.  The first
spotless day after sunspot group 1008's last appearance was Tuesday,
November 18 and the last spotless day before group 1009 emerged was
Tuesday, December 9.  As expected, this was another Cycle 24 group,
emerging far south of our Sun's equator.

This weekend is the ARRL 10-meter contest, and it would be great to
have enough sunspots to drive the MUF (Maximum Usable Frequency)
above 28 MHz, but that doesn't seem likely, as group 1009 is near
the western limb of the visible solar disk.

What level of solar activity would we need in order to see the MUF
above 28 MHz?  That varies according to the locations of the two
stations trying to communicate, the season, and the time of day.
For example, if the date is December 13, the path from Cleveland,
Ohio to Dallas, Texas is likely to briefly have an MUF at 28.0 MHz
around 1730z, if the average sunspot number was at least 105 for
several days.

In our example, if the average sunspot number for several days was
125, the three-hour period from 1700-2000z would have an MUF above
28 MHz, and the 1730-1800z period would likely have the best
signals.

If we calculate the path from Boston to Atlanta for the same date,
instead of 105, the average sunspot number for several days should
be at least 131 to reach an MUF of 28.0 MHz.

But don't expect 10 meters to be unusable this weekend.  An MUF
above 28 MHz is desirable for very reliable communications, but
perhaps sporadic-E skip will offer surprises.  Summer sporadic-E is
more intense, but this time of year we should see some sporadic-E.

A few weeks ago Vic Woodling, WB4SLM of Centerville, Georgia wrote
about an experience on 30 meters in the middle of the day, copying
strong European stations, and also 5R8IC working into Europe from
Madagascar, but with weaker signals on Vic's end.  This was at
1630z, and when Vic came back to the radio at 1830z, they were even
stronger.

Although in Vic's experience this is uncommon, a check with a
propagation program for 30 meters on November 22 with zero sunspots
between Georgia and England shows propagation closely matching his
report.  At 1630z it shows the relative signal level at 15 db, and
then at 1830z it jumps to 29 db.

But if he looks further east to the Czech Republic, the signals stay
around the level that they would be for England at 1630z, all
through the same period.

Ed Clulow, N7TL of Portland, Oregon commented on 75 meter conditions
during the SSB Sweepstakes Contest, which was November 15-17.  He
uses an inverted-vee dipole, and said after dabbling in contests for
several decades, he has never seen propagation like it was on
Saturday evening, and said it sounded more like 20 meters.  He
worked Midwest and East Coast stations with ease, snagging them on
the first or second call.  He knows some hams never venture below 20
meters, and thinks some of us may be missing good propagation at the
bottom of the sunspot cycle.

Dave Bennett, VE7YJ of Aldergrove, British Columbia wrote, "Carrying
on from WE0H's report on 600 meter activities, I have noted in the
past week or so reception from the powerful Far Eastern Russian
broadcasters on 153, 180, 189, 234, and 279 KHz. They were at their
best on November 29, around 0700z, but were heard as early as 0440z.
They haven't been as good the last couple of days, but were still
detectable. I'm using an old IC-751A with a 160M inverted V antenna
and could probably get even better results with a bigger antenna.
Last few nights 160 meters has been spotty as well. VE6s were
strong, but the Century Club net on 1892 has been poor, whereas the
week before I was hearing stations as far east and south as Texas
and Ohio."

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/.

Instructions for starting or ending email distribution of this
bulletin are at http://www.arrl.org/w1aw.html#email.

Sunspot numbers for December 4 through 10 were 0, 0, 0, 0, 0, 0, and
13 with a mean of 1.9.  10.7 cm flux was 69.6, 68.8, 69.1, 69, 68.5,
68.7, and 70.8 with a mean of 69.2.  Estimated planetary A indices
were 6, 10, 7, 6, 5, 0 and 2 with a mean of 5.1.  Estimated
mid-latitude A indices were 4, 7, 14, 6, 1, 1 and 2 with a mean of
5.
NNNN
/EX