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ARRL Propagation Bulletin ARLP033 (2008)

ARLP033 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 33  ARLP033
From Tad Cook, K7RA
Seattle, WA  August 8, 2008
To all radio amateurs 

ARLP033 Propagation de K7RA

As mentioned in last week's Bulletin, Carl Luetzelschwab, K9LA, is
filling in for your regular reporter Tad Cook, K7RA.

For the reporting period August 1 through August 7, solar activity
was at very low levels and the geomagnetic field was at quiet
levels.  Solar activity is expected to be very low for the next
several days.  As for geomagnetic field activity, the Australian
Space Forecast Centre issued a geomagnetic disturbance warning on
August 6 for quiet to unsettled and then unsettled to active
conditions (with possible minor storm periods) on August 8 and
August 9, respectively.

Other than a new-cycle magnetic dipole on August 3 that didn't turn
into a sunspot region, the Sun was again blank for the entire
reporting period.  Kind of sounds like a recording, doesn't it? A
good summary is:

Here we sit at solar min 
Wondering when Cycle 24 will begin

It seems like we've been at solar minimum forever.  In fact, there
have been several news releases hinting that this solar minimum
period between Cycle 23 and 24 is unusual.

The analysis of recent spotless days compared to historical spotless
days (see led Dr.
David Hathaway (NASA solar physicist) to conclude that nothing is
unusual about this solar minimum period.  Another way to look at
solar minimum is to look at the duration when the smoothed sunspot
number is below 20.  Historically this duration has ranged from a
short 17 months to a long 96 months, with an average of 37 months.
Cycle 23 descended below 20 in February 2006, and Cycle 24 is
predicted to ascend above 20 in early 2009.  That's around 36
months, so everything appears to be pretty normal so far and agrees
with Dr.  Hathaway's conclusion.  We'll just have to be patient
until Cycle 24 starts ramping up.  The good news is that we have
seen three sunspot regions tied to Cycle 24 (January 4, April 13,
and May 5), so it's coming.

What can you do around solar minimum?  One activity would be to get
on the low bands for the Fall/Winter season - the low bands should
be very good.  Another activity would be to take advantage of summer
sporadic E (and in December, too, but it's not as prevalent).  For
example, last weekend provided some excellent 6 Meter propagation.
And participants (your author included) in the CW running of the
North American QSO Party (sponsored by the National Contest Journal)
enjoyed 10 Meter and 15 Meter sporadic E openings (which likely
happens a lot more than we think - a dead band may not be dead, just
unoccupied).  And since mid latitude sporadic E is not tied to
sunspots, we can have fun throughout an entire solar cycle.

Speaking of sporadic E, last week's Bulletin reported N4KZ working
EA8/DL6FAW on 6m on both CW and SSB.  This brought a reply from
Norbert Scherer, DL6FAW.  Norbert reports that he's been operating
on 2m for many years, but his 6m activity is relatively new.  Since
2006 he has been running 100W to a simple 5-element Yagi when in

Norbert continues:  ''In the first weeks I only heard North America
in the middle of the day.  I never expected any opening after
midnight local time.  But by carefully monitoring the beacons I was
surprised to hear, for example, WZ8D/B late in the evening.
Sometimes I started to call CQ and there was no reply at all.  The
following day, when I heard the beacon again and nothing else, there
were ten people calling at the same time.  Tim, KY5R, told me last
week that I was the only signal on the band he could hear.

I hope there will be more good propagation to NA in the coming
weeks, although the sunspot number is Zero!  I checked out some
websites listing solar activity, sunspot number, K-index, solar
winds, etc.  for July 2008.  But I couldn't find any correlation
between the data provided there and my log.''

DL6FAW's attempt to correlate 6m Es to sunspots came out as expected
- as stated earlier, there doesn't appear to be any tie between
where we are in a sunspot cycle and the occurrence of mid latitude
sporadic E.

Finally, in last week's Bulletin Jim Henderson, KF7E, provided some
good observations and comments about the day-to-day variability of
the ionosphere.  A good supporting example of his observations is
the F2 region MUF over the Millstone Hill ionosonde (in
Massachusetts), assuming it's the mid point of a 3000 km hop.  In
July, when the solar flux was for all intents and purposes constant,
the 3000 km MUF varied from a low of 8.9 MHz to a high of 19.6 MHz.
KF7E's comments, along with the Millstone Hill data, are in
agreement with ionospheric studies showing that although solar
radiation is the instigator of the ionization process, two other
factors appear to be more significant in determining what the F2
region ionosphere is doing right now.  These two factors are
geomagnetic field activity and events in the lower atmosphere
coupling up to the ionosphere.

What does all that mean? It simply means plugging the daily solar
flux into your favorite propagation prediction program really
doesn't tell you what the ionosphere is doing today.  This
day-to-day variability is the reason our prediction programs were
designed to be statistical over a month's time frame.  We do not
have daily predictions, and the developers never intended that they
be daily predictions as they were aware of the unpredictability of
the day-to-day variation of the ionosphere.  Perhaps some day we'll
figure all this out, but for now the best way to tell if one of the
higher bands is open is to listen to the NCDXF/IARU beacons

For more information concerning radio propagation, see the ARRL
Technical Information Service at  For a detailed
explanation of the numbers used in this bulletin, see  An archive of
past propagation bulletins is at
Monthly propagation charts between four USA regions and twelve
overseas locations are at
Instructions for starting or ending email distribution of this
bulletin are at

Sunspot numbers for July 31 through August 6 were 0, 0, 0, 0, 0, 0,
and 0 with a mean of 0.  10.7 cm flux was 65.5, 66.1, 66.2, 65.5,
66.2, 66.5, and 67 with a mean of 66.1.  Estimated planetary A
indices were 4, 3, 3, 4, 4, 3 and 4 with a mean of 3.6.  Estimated
mid-latitude A indices were 4, 2, 2, 3, 3, 3 and 5 with a mean of


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