Propagation Forecast Bulletin #37 de K7RA:

ZCZC AP37
QST de W1AW
Propagation Forecast Bulletin 37 ARLP037
From Tad Cook, K7RA
Seattle, WA September 17, 2010
To all radio amateurs

SB PROP ARL ARLP037
ARLP037 Propagation de K7RA

Average daily sunspot numbers this week dropped nearly 23 points to
15.6, and geomagnetic indices were quiet. The average daily solar flux
was 78.1, but the latest prediction from USAF and NOAA is for rising
solar flux values. The September 17-23 projection has solar flux values
at 85, 85, 86, 86, 86, 87, and 88, which is well above last week's
average. Solar flux hasn't been to 88 or higher since August 7 (90.5),
and before that July 21 (89.1).

The same forecast shows planetary A index for the same period at 8, 5,
5, 5, 18, 18 and 15, which indicates rising geomagnetic activity along
with the increased solar activity. Geophysical Institute Prague predicts
quiet to unsettled conditions September 17, quiet September 18-19, quiet
to unsettled September 20, and unsettled conditions September 21-23.

The Autumnal Equinox occurs Wednesday, September 22 at 11:09 PM EDT,
which is 0309 UTC on September 23. With the northern and southern
hemispheres bathed in equal amounts of light, expect better worldwide HF
propagation, although solar activity continues at a low level which does
not support an MUF into the higher frequencies over most paths.

By the way, the bulletin didn't mention this at the beginning of
September, but the monthly averages of daily sunspot numbers have risen
the past few months. For June, July and August the average daily sunspot
numbers for each month were 18, 23.1 and 28.2, and so far in September
the average for the first 16 days is 29.6.

Last Saturday, September 11, AC7SB, W7RDP and WE7X went to the Suntop
forest fire lookout station in the Cascade Mountains of Washington
State. The location is 47.041 deg N, 121.5965 deg W, While there they
used a telescope and filter to view an emerging sunspot, W7RDP and WE7X
operated the ARRL VHF Contest, and AC7SB worked 40 meter CW using a
tape-measure dipole. You can see a photo album of their adventure at,
http://tinyurl.com/33z5ty3.

Scott Bidstrup, TI3/W7RI in Costa Rica sent an article about Tsunami
waves disrupting the ionosphere. Read it at, http://snipurl.com/13z1o4.

Mike Downing, KC0Y of Broomfield, Colorado is getting back on 6 meters
after many years, and wonders how things have changed regarding TVI? He
mentioned that most people are using cable TV and the broadcasters have
left Channel 2, which had a lot of the problems in the past. According
to what I've heard, the situation is much better than it was decades
ago, for the reasons that Mike mentioned.

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,
http://arrl.org/propagation-of-rf-signals. For an explanation of the
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
propagation bulletins is at,
http://arrl.org/w1aw-bulletins-archive-propagation. Find more good
information and tutorials on propagation at,
http://mysite.ncnetwork.net/k9la/index.html.

Monthly propagation charts between four USA regions and twelve overseas
locations are at, http://arrl.org/propagation.

Sunspot numbers for September 9 through 15 were 0, 11, 11, 26, 17, 24,
and 20 with a mean of 15.6. 10.7 cm flux was 73.7, 75.3, 78, 78.3, 79.5,
80.7 and 81.2 with a mean of 78.1 Estimated planetary A indices were 4,
2, 1, 1, 2, 9 and 7 with a mean of 3.7. Estimated mid-latitude A indices
were 4, 2, 1, 1, 1, 7 and 4 with a mean of 2.9.
NNNN
/EX

Source: W1AW Bulletin via the ARRL.