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ARRL Propagation Bulletin ARLP033 (2010)

ARLP033 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 33  ARLP033
From Tad Cook, K7RA
Seattle, WA  August 20, 2010
To all radio amateurs 

ARLP033 Propagation de K7RA

Thanks so much to Tomas Hood, NW7US, who wrote last week's bulletin
while K7RA was in California at dance camp.  Tomas writes the weekly
propagation column for CQ magazine, and he has an excellent web site
devoted to propagation at

Tomas mentioned in last week's bulletin that the August 11 sunspot
number of 66 is the highest recorded for cycle 24, but actually
there were higher values recorded on May 4-5, when the sunspot
number was 70 and 77, as you can see at
See values from the current quarter at
To see higher sunspot numbers, we must look back to the downward
slide of cycle 23 on April 12, 2006 when the sunspot number was 79.
The 2006 data is at

Sunspot numbers and solar flux declined this week, with average
daily sunspot numbers down nearly 17 points to 36.1, and average
daily solar flux down 1 point to 83.5.  In the previous week,
average daily sunspot numbers had risen nearly 33 points to 53.

New sunspot groups appeared on August 11, 13 and 16, but on Tuesday
and Wednesday (August 17-18), total sunspot area was one-fifth what
it was on August 16, less than one-seventh the area on August 14,
and less than one-fourteenth the area of August 12.  On August 12,
14, 16 and 18 the daily sunspot number was 50, 31, 39 and 23, and on
August 19 it was 11, which is the minimum non-zero sunspot number.

Projections for solar flux over the next ten days, August 20-29, are
78, 78, 77, 77, 79, 80, 82, 84, 82, and 81.  Predictions for
planetary A index over those same days are 5 on August 20-23, 6 on
August 24, 12 on August 25-26, and 5 on August 27-29.

Geophysical Institute Prague predicts quiet conditions for August
20-22, quiet to unsettled August 23, and unsettled August 24-26.

Carl Luetzelschwab, K9LA has a new propagation column out today in
WorldRadio online.  See it on pages 24-26 at

Greg Andracke, W2BEE of Pine Plains, New York says he will visit
Saint Vincent and the Grenadines in the Caribbean in mid-December,
and wants to know what night time propagation might be like on 20
and 30 meters.

Running some numbers with W6ELprop shows that the local sunset time
is 2138z on December 15.  Propagation back to anywhere in the USA
doesn't look promising after dark, but paths to South Africa and
South America look good.

Thanks to David Moore of Morro Bay, California and Mark Downing,
WM7D for sending a couple of articles on a possible explanation for
weak solar activity.  The articles are at

Bob Forsman, WK5X of Stuart's Draft, Virginia commented about an
item in the August 6 bulletin, ARLP031.  "KA3JAW's reception of
Channel 2 from Ontario probably had nothing to do with the CME.
It's likely just garden-variety late-season sporadic-E, in my
opinion; and I'm pretty sure that you realize this also.  1300 miles
is close to the maximum distance possible via single-hop, but it
isn't terribly unusual.  The MUF of the e-layer was likely around
58-60 MHz at the mid-point".

Dean Lewis, W9WGV of Palatine, Illinois wrote "While I realize this
is old news, it might at least be worth the perspective.  Being used
to 20/30/40 meter propagation, I didn't have any particular
appreciation for contacts I'd made on 6 meters.

Having just purchased a new Icom 703, I thought I'd give it a try on
6 during the June VHF QSO Party.

Without a 6M antenna, I managed to tune up my 66 ft. end-fed 40
meter wire through a short length of coax as something of an
off-center resonant feedline dipole (??!).

From our QTH 25 miles northwest of Chicago, I worked 11 states with
the 703's 10W (CW) output:  AL, FL, GA, IL, MA, MS, NH, SD, TX, UT,
and WI.  (I QSL 100, with an SASE; the return cards have all

Family events over the weekend limited my air time; I could have
done more, I'm sure.

Oh; and BTW, the antenna is indoors (typical townhouse "CC&R's").

Now I understand why they call it 'magic'".
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 at For an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at  Find more good
information and tutorials on propagation at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for August 12 through 18 were 50, 51, 31, 33, 39,
26, and 23 with a mean of 36.1. 10.7 cm flux was 83.8, 83.7, 85.2,
85.6, 84.7, 81.1 and 80.3 with a mean of 83.5. Estimated planetary A
indices were 4, 4, 3, 5, 7, 5 and 5 with a mean of 4.7. Estimated
mid-latitude A indices were 3, 3, 2, 5, 4, 3 and 3 with a mean of


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