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ARRL Propagation Bulletin ARLP025 (2008)

ARLP025 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 25  ARLP025
From Tad Cook, K7RA
Seattle, WA  June 13, 2008
To all radio amateurs 

ARLP025 Propagation de K7RA

Sunspot 998 emerged this week, another old Cycle 23 sunspot near the
equator.  Daily sunspot numbers for June 10-12 were 14, 11 and 13.
Last Sunday, June 8 had the lowest 10.7 cm solar flux value I've
ever seen, 64.9 at the observatory in Penticton.  The noon reading
is the official daily sunspot number, and the value observed that
morning at 1700z was actually a tiny bit lower at 64.8.  The only
value this low I have in my records was almost a dozen years ago
near the last solar minimum, July 19, 1996.

10.7 cm solar flux is a measurement of energy at 2.8 GHz, gathered
by an antenna in British Columbia.  The facility is the Dominion
Radio Astrophysical Observatory, which sits 168 miles northeast of
my Seattle location at approximately 49.322 degrees North latitude,
119.621 degrees West longitude.

The solar flux value is a general indicator of solar activity, but
not as useful as sunspot numbers for predicting propagation.  You
can see all three daily flux readings at,
Although this just accesses a text file on a server using file
transfer protocol, that same address works in a web browser.  The
flux value you want is in the fluxobsflux column.  The fluxdate
column shows the date the value was observed, with a format in which
20080613 means June 13, 2008.  The fluxtime column shows the time of
the observation, with a format in which 170000 means 1700z.  The
official daily solar flux is measured at 2000z, or 200000 in

Paul Kelly, NN5G of Oklahoma City asks about expected stateside
coverage for a net on 20 meters at 2000z, with net control in the
middle of the contiguous 48 states.  He is trying to use the charts
at to determine a better time
for the net.

I suggested he use W6ELprop, which we described in Propagation
Forecast Bulletin ARLP020 (see  This way he can
test over any path, and account for seasonal variations in addition
to time of day factors.  Propagation prediction software isn't
perfect, but can give you good odds on what is likely to work, given
the time of day, the particular path, the band used, the season, and
an average of recent sunspot activity, or the predicted smoothed
sunspot number for the month.

Testing the path on 20 meters from my home to the center of the
country, 2000z seems a good time of day.  Same thing with Boston,
and the few other places I examined, and to many places this Summer
later in the day and on into the evening look quite good.  It gets
tougher if the path is shorter, and other choices such as 40 meters,
or even 30 meters (since his net uses a digital mode) is a good

By the way, if you check his personal page at you'll read a sad story of his literally
one-hour long Novice career as a 13-year old, cut dead short in 1960
by neighbors and family going ballistic over TVI and Ed Sullivan.  A
chance encounter 40 years later led to relicensing and his happy
resumption of his amateur radio avocation.

Not much sunspot activity of note, but this is the sporadic-E
season, so some interesting work has been popping up on 6 and 10

This is late, but two weeks ago this bulletin reported from Julio
Medina, NP3CW in Puerto Rico and his 6-meter fun on May 22-23.
Subsequent to that he had much success on May 26-29.  On May 26 he
reported a nice opening to Europe, mostly to Spain, Portugal and the
Canary Islands.  May 27 he worked F6FHP, F1PUX in JN26, DK1MAX in
JN58, SP6GWB in JO80, PA2M in JO21, and PA0O and 9Y4D in FK90.

The following day on May 28 he worked G4DEZ in JO26, CN8KD in IM63
(Morocco), and VE1YX in FN74.  On May 29 it was on to FM5LD in on
CW, K5RQ, K4SN in EL96, AA4ET in EL96, W4ZE, 8P9TS in GK03, and

Vince Varnas, W7FA sent a very encouraging 6-meter report:

"There was a GREAT (for the bottom of the sunspot cycle) 6-meter
sporadic-E opening to Japan on June 10 from Portland, Oregon (CN85).
The band was open from about 2245-2330z. I worked 16 stations in six
JA call areas on SSB during this time with signals averaging about
S-5. It wasn't as good as the F2 openings in years gone by. I was
still in great demand with a pile up on me of about 4-5 JA stations
calling for 45 minutes on 50.110 MHz."

Vince also worked two Puerto Rican stations, KP4EIT and WP4G on 6
meters on June 9 around 1850z.

Johnny Kiesel, KE7V of Washington State gives a similar 6-meter
report for June 10.  He worked 38 Japanese stations in all ten
districts, beginning at 2225z with JE1BMJ and ending at 2327z.  That
is about one JA every 98 seconds.

He reported that JE1BMJ over the past week worked W4, 5, 7, 8, 9 and
0 call areas on 6-meters, and may have set a sporadic-E distance
record, 13,000 km to HI3TEJ in the Dominican Republic on June 11.

There is a nice one-page article on 6-meter sporadic-E propagation
in the July 2008 issue of QST, titled "Summer E-skip and the Magic
Band."  Check it out on page 55.  Written by Gene Zimmerman, W3ZZ,
the VHF Editor for QST, it has many good suggestions for summertime
fun on 6-meters, and a good outline of the fundamentals.  I'm going
to read it again right now before I write another word about E-layer

The Summer Equinox is just one week away.  We hope for more frequent
and larger sunspots, but most are grateful for any darkness
shadowing the solar disc.  This weekend more sporadic-E propagation
would be nice during the ARRL June VHF QSO Party.  The key to
scoring is to work many grid squares, which are multipliers.  See
the rules at,

NASA predicts more of the same quiet conditions, with slight
possible unsettled conditions on June 18, with a planetary A index
of 12.  They expect solar flux to stay below 70 until mid-July.

Geophysical Institute Prague expects quiet conditions for June 13,
quiet to unsettled June 14, unsettled June 15-18, and quiet to
unsettled June 19.

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation, see the ARRL
Technical Information Service web page 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 June 5 through 11 were 0, 0, 0, 0, 0, 14, and 11
with a mean of 3.6.  10.7 cm flux was 66.4, 65.9, 65.6, 64.9, 66,
66.2, and 65.7 with a mean of 65.8.  Estimated planetary A indices
were 2, 8, 12, 7, 5, 4 and 4 with a mean of 6.  Estimated
mid-latitude A indices were 3, 7, 10, 5, 2, 1 and 3, with a mean of


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