ARRL

ARRL Propagation Bulletin ARLP036 (1999)

SB PROP @ ARL $ARLP036
ARLP036 Propagation de K7VVV

ZCZC AP36
QST de W1AW  
Propagation Forecast Bulletin 36  ARLP036
From Tad Cook, K7VVV
Seattle, WA  September 3, 1999
To all radio amateurs 

SB PROP ARL ARLP036
ARLP036 Propagation de K7VVV

Sunspots and solar flux were both up this week, with sunspot number
averages rising over 100 points.  Average solar flux was up nearly
34 points, and flux values reached a new high for cycle 23 on
Saturday, at 248.4.  The last time flux values were this high was on
the downside of cycle 22 on February 26, 1992 when it was 253.

Geomagnetic indices were fairly active, with September 1 the most
active day.  Planetary A index was 22, and the K indices were 4 or 5
over most periods.  In higher latitudes, the College index (from
Alaska) had an A index of 37 on that day, with K indices as high as
6.

Solar flux has been falling since the weekend, and over the next few
days (Friday through Sunday) the values are predicted at 150, 140
and 130.  Planetary A index is forecast at 10 for all three days,
so conditions should be stable for this weekend's All Asia DX Phone
Contest.

Beyond the weekend look for solar flux to bottom out around 125 on
September 8 or 9, then rise above 140 after the middle of the month,
peaking around 220 on September 23 or 24.  September 12-16 should
have unsettled geomagnetic conditions, with A indices around 15.

August showed a continued upward trend in solar flux.  Average flux
values for April through August were 117.2, 148.4, 169.8, 165.6 and
170.7.

KF7E sent the URL http://space.rice.edu/ISTP/justdials.htm, along
with some comments about the ionosphere's D layer.  Jim mentioned
that in the summer the D layer is thicker and more absorptive, and
the LUF (Lowest Usable Frequency) increases.  Since the MUF (Maximum
Usable Frequency) is lower, this puts a ''squeeze'' on propagation,
where there are fewer usable HF bands.  But he also mentioned a
tradeoff.  While the MUFs are lower, 20 meter propagation extends
long into summer evenings due to slower ion recombination, but
closes sooner in the winter because of less ionization from sunlight
and faster recombination.

Sunspot numbers for August 26 through September 1 were 176, 194,
225, 229, 212, 190 and 137 with a mean of 194.7.  10.7 cm flux was
222.2, 223.1, 248.4, 218.2, 198.1, 182.7 and 162.8, with a mean of
207.9, and estimated planetary A indices were 13, 13, 14, 10, 20, 18
and 22, with a mean of 15.7.

Here are some path projections for the All Asia DX Phone Contest
this weekend.

From East Coast USA to Japan, 80 meters 0930-1030, 40 meters
0900-1100, 20 meters 1130-1500 UTC, 15 meters 2100-2230 UTC.  To
UA0, 80 meters 0930-1000 UTC, 40 meters 0700-1130 UTC, 20 meters
1100-1200 UTC, 15 meters possibly 2200-0000 UTC.  To the
Philippines, 40 meters 1000-1100 UTC, 20 meters 1130-1400 UTC.

From the geographic center of the 48 U.S. states to Japan, 80 meters
0900-1230 UTC, 40 meters 0800-1330 UTC, 20 meters 1300-1700 UTC and
0500-0630 UTC, 15 meters 2030-0400 UTC, and 10 meters possibly
2300-0000 UTC.  To UA0, 80 meters 0830 UTC-1230 UTC, 40 meters
0630-1300 UTC, 20 meters 2130-0630 UTC, 15 meters possibly 2230-0230
UTC.  To the Philippines, 80 meters 1000-1230 UTC, 40 meters
0930-1300 UTC, 20 meters 1300-1600 UTC, 15 meters 2130-0330 UTC.

From the USA West Coast to Japan, 80 meters 0900-1430 UTC, 40 meters
0800-1500 UTC, 20 meters 0400-0930 UTC and 1430-1600 UTC, 15 meters
2030-0600 UTC, and 15 meters possibly 2230-0100 UTC.

To the Philippines, 80 meters 1000-1430 UTC, 40 meters 0930-1500
UTC, 20 meters 0700-0930 UTC and 1400-1800 UTC, 15 meters 2130-0600
UTC, 10 meters possibly 2200-0130 UTC.  
NNNN
/EX