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ARRL Propagation Bulletin ARLP015 (2002)

ARLP015 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 15  ARLP015
From Tad Cook, K7VVV
Seattle, WA  April 12, 2002
To all radio amateurs 

ARLP015 Propagation de K7VVV

Sunspot numbers and solar flux rose again this week.  Average daily
sunspot numbers for April 4-10 were up nearly 40 points, and average
daily solar flux rose by over 11 points, when compared with the
seven-day period ending April 3.  Solar flux is expected to decline
over the short term, to below 190 after this weekend, and below 180
after next Wednesday.  There is a chance of geomagnetic unrest this
weekend due to a solar flare and coronal mass ejection on April 10
at 1230 UTC.  This wasn't aimed exactly at earth, so the effects are
a little hard to predict, but Thursday morning's forecast from the
U.S. Air Force has the planetary A index at 12 on Friday, 15 on
Saturday and 20 on Sunday.

We got mail this week via  N2YQZ wrote from
Eastern New York to comment that over the past few weeks he has
noticed more frequent dead times on 10 meters, particularly around

N0JK reported that on April 6, K4SUS in Florida worked Japan, Taiwan
and China on six meters, all via long path.  N0JK also worked LU1YBB
in Argentina around 1904 UTC on April 3 from Kansas via F2 layer
propagation on six meters.  He reports that more seasonal north-
south propagation on six meters is noted around this time of year,
particularly from the southern tier of the United States.  He says
that peak times are around early afternoon.

KD2FT wrote to say he reads this bulletin via email, and plans to
take an extended cruise in his boat this fall.  He wants to get
basic solar flux and geomagnetic alerts via HF radio.  Best to tune
into WWV at 18 minutes after each hour, or WWVH at 45 minutes past
the hour.  WWVH is on Kauai in Hawaii, and broadcasts on 2.5, 5, 10
and 15 MHz.  WWV is in Fort Collins, Colorado, and is on 2.5, 5, 10,
15 and 20 MHz.  Of course the precise time service from these
stations is also useful if you need to set an old style ship's

N0YD wants to know, in a nutshell, how the numbers reported in this
bulletin will affect propagation.  He would like to know if
conditions will get better or worse, or when we can expect radio

A good place to look for an explanation is K9LA's piece at, but N0YD would like a
shorter summary of the upcoming week in each bulletin.  Well,
basically on HF we like to see lots of sunspots (or high solar flux)
and very low geomagnetic activity, as reported in K and A indices.
This past week had very low geomagnetic activity, so that was good.
The fact that solar flux was higher over the past week is generally
good, although it really takes a big movement in the numbers to have
a noticeable effect.  There is a possibility for higher geomagnetic
activity this weekend, and that might be bad for high frequency
propagation, partly because of increased absorption.  But it could
be good for VHF in terms of auroral propagation, where you can
bounce your VHF signals off of an aurora by aiming your antenna
north.  Solar flux is expected to be slightly lower next week, but
not enough to make a big difference.

10, 15 and 20 meters will be the focus this weekend for the Japan
International HF CW DX Contest.  Stations outside of Japan will
score points by working Japanese stations.  Here are a few path
projections for this weekend from various locations.  Those that are
polar paths to Japan could have a rough time if the K index is above

From Boston, MA, try 20 meters 0500-0630, 0830-1600, 2000-0130 UTC,
15 meters 1300-1430, 2000-0130 UTC, 10 meters possibly 1200-1400,
2000-0200 UTC.  This is a polar path.

From New York City, 20 meters 0500-0630, 0930-1600 UTC, 15 meters
1300-1430, 2000-0200 UTC, 10 meters possibly 1200-1400 or 2000-0230
UTC.  This is a polar path.

From Toronto, Ontario/Buffalo, New York, 20 meters 0500-0630, 1000-
1630 UTC, 15 meters around 1400 and 2000-0230 UTC, 10 meters
possibly 1230-1400 or 2000-0300 UTC.  This is a polar path.

From Cleveland, OH, 20 meters 0500-0630, 0800, 1000-1630 UTC, 15
meters 1300-1430, 1930-0300 UTC, 10 meters possibly 1300-1400 or
1930-0200 UTC.  This is a polar path.

From Atlanta, 20 meters 0500-0800, 1030-1530 UTC, 15 meters 1300-
1430, 1930-0500 UTC, 10 meters possibly 1300-1400 or 1930-0400 UTC,
and within the last period, very good possibility around 2030-0030
UTC, especially at 2200 UTC.  This is a polar path.

From Miami, 20 meters 0600-0730, 1000-1400 UTC, 15 meters 1200-1400,
2000-0500 UTC, 10 meters good around 2130-2300 and possible as early
as 2000 or as late as 0400 UTC, or possibly 1230-1400 UTC.  This is
a polar path.

From the geographic center of the contiguous 48 United States, 20
meters 0430-0830, 1200-1630 UTC, 15 meters possibly 1330-1500 UTC
and probably 1930-0530 UTC, 10 meters 2030-0200 UTC.

From Dallas, Texas 20 meters 0430-0900, 1130-1630 UTC, 15 meters
1330-1430, 1930-0600 UTC, 10 meters very good 2030-0130 UTC.

From Salt Lake City, 20 meters 0230-0930, 1300-1600 UTC, 15 meters
1930-0600 UTC, 10 meters 2000-0300 UTC.

From Omaha, Nebraska, 20 meters 0500-0830, 1200-1630 UTC, 15 meters
1400-1500, 1930-0500 UTC, 10 meters 2000-0100 UTC.

From Denver, 20 meters 0300-0900, 1230-1600, 1800-1900 UTC, 15
meters 1430 UTC, 1930-0600 UTC, 10 meters 2100-0200 UTC.

From Los Angeles, 20 meters 0230-1030, 1230-1630 UTC, 1800-2000 UTC,
15 meters 1400-1500, 1930-0800 UTC, 10 meters excellent 2130-0200,
opening as early as 2000 to as late as 0730 UTC.

From the San Francisco Bay Area, 20 meters 0230-1030, 1330-2030 UTC,
15 meters 2000-0730 UTC, 10 meters 2100-0200 UTC.

From Seattle, 20 meters 0130-0930, 1430-2200 UTC, 15 meters 2000-
0530 UTC, 10 meters possibly 2030-0430 UTC.

From Edmonton, Alberta, 20 meters 0300-0930, 1330-1730, 1830-2100
UTC, 15 meters 2030-0300 UTC, 10 meters possibly 2100-0400 UTC.
This is a polar path.

From Alaska (between Anchorage and Fairbanks) 20 meters 1600-1230
UTC, 15 meters 2000-0730 UTC, 10 meters possibly 2000-0800 UTC.
This is a polar path.

From Hawaii, 20 meters open all the time, best 0830-1700 UTC,
weakest 2300-0200 UTC, 15 meters 1900-1230 UTC, strongest signals
0900-1200 UTC, 10 meters excellent conditions 2100-1100 UTC, with
strongest signals toward the end of the period.

Sunspot numbers for April 4 through 10 were 176, 200, 234, 227, 245,
212 and 220 with a mean of 216.3. 10.7 cm flux was 216.2, 217.4,
206.3, 207.9, 206.2, 205 and 194.3, with a mean of 207.6, and
estimated planetary A indices were 8, 6, 5, 7, 5, 6 and 7 with a
mean of 6.3.


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