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ARRL Propagation Bulletin ARLP041 (2012)

ARLP041 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 12, 2012
To all radio amateurs 

ARLP041 Propagation de K7RA

Another decline in sunspot activity this week, but based on activity
over the past few days and projected solar flux values it is making
a steady recovery.

Average daily sunspot numbers dropped from 73 to 51.7, a difference
of 21.3 points. But the past three days saw sunspot numbers higher
(63, 71 and 82) than the average, and climbing.

The average of daily solar flux was off 23.8 points to 104.9, and
like the sunspot figures, the past three days saw solar flux values
(106.2, 112 and 116.6) higher than the average for the week, a good
indicator of the rising activity.

Predicted solar flux from the Thursday, October 11 NOAA/USAF
forecast is 115 on October 12-13, 120 on October 14-17, then 125,
130, 150 and 145 on October 18-21, 140 on October 22-23, 135 on
October 24-27 and 130, 125, 120 and 115 through the last day of
October. Solar flux is then predicted to dip below 100 on November
4-8 and peak at 145, 150 and 145 on November 15-17.

October 12-17 predicted planetary A index is 5, 5, 12, 12, 10 and 8,
then 5 on October 18 through November 3, then 18, 20, 12 and 8 on
November 4-7, 5 on November 8-10, then 8, 12 and 10 on November
11-13 and 5 after that, through the end of the 45 day forecast

We always get a bit different perspective on upcoming geomagnetic
conditions from OK1HH.  He predicts quiet to active conditions
October 12, quiet to unsettled October 13, quiet on October 14,
quiet to unsettled October 15, quiet October 16, quiet to active
October 17, quiet to unsettled October 18-19, quiet on October
20-22, quiet to active October 23, quiet October 24-27, active to
disturbed October 28, mostly quiet October 29-30, quiet October 31
and November 1, quiet to active November 2, and mostly quiet
November 3.

October 8-9 showed the most geomagnetic activity during the past
week, with planetary A index at 35 and 42, mid-latitude A index at
21 and 32, and the high latitude college A index at 66 and 54. This
activity was triggered by a coronal mass ejection on October 8.  The
predicted rise in planetary A index to 12 on October 14-15 is
because of a solar wind spewing from a coronal hole, which should
rotate into a geo-effective position during that time.

John King, EI2HVB said on October 10 he worked W1AW in Newington, CT
on 20 meter CW using only 2 watts into a sloping V dipole from an
MFJ Cub transceiver. This was right after seeing aurora from his QTH
for several nights in a row.  Of course, unlike here on the West
Coast, a path from W1AW to Ireland is not anything near a polar
route, so it would not be as affected by geomagnetic unrest as a
contact to Europe from the West Coast would be. In Seattle, my
bearing to Letterkenny, John's QTH, would be 35.7 degrees, close to
the auroral zone, and his return path would be at 316.9 degrees.
But from W1AW short path would be toward 49.2 degrees, and return
path is 280.4, further away from the polar path.

Dean Lewis, W9WGV of Palatine, Illinois wrote: "While working county
after county in the California QSO Party on the low end of 10 meters
on Saturday, October 6, I heard PY2XC calling CQ DX. Had a friendly
exchange with Carlos; 559 signals both ways, no QSB. He was running
200W to a dipole; due to outside antenna restrictions I run an Icom
703 (10W max) into an end-fed 65 foot wire (half wave on 40 meters)
indoors along the upstairs ceiling (I've had the most supportive XYL
in hamdom for 42 yrs). It resonates at a low SWR on 40, 20, 15, and
10 meters without a tuner. says the distance is 5,248 miles
from my QTH (25 miles NW of Chicago). A half hour later his signal
was S9+."

I received some interesting emails this week from a ham who has one
of those FCC experimental licenses that allows him to operate below
the AM broadcast band to test antennas, radios and propagation. I
was about to present some of his observations here in the bulletin,
but just now noticed that at the very top of his first email was a
statement about "this is not intended for publication."  That's
unfortunate, as he wants to attract others to do what he is doing,
but now I feel restrained from quoting our correspondence. If you
send me an email, normally you can assume that I might quote you as
well as make edits for brevity and readability.

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 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 October 4 through 10 were 56, 55, 39, 37, 41,
63, and 71, with a mean of 51.7. 10.7 cm flux was 109.5, 106.2,
98.8, 98.1, 103.4, 106.2, and 112, with a mean of 104.9. Estimated
planetary A indices were 3, 4, 6, 5, 35, 42, and 10, with a mean of
15. Estimated mid-latitude A indices were 3, 3, 5, 4, 21, 32, and 6,
with a mean of 10.6.


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