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1993-04-25
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SB PROP @ ARRL $ARLP016
ARLP016 Propagation DE KT7H
QST DE W1AW
Propagation Forecast Bulletin 16 ARLP016
From Tad Cook, KT7H
Seattle, WA April 23, 1993
To All Radio Amateurs
Solar flux dropped significantly last week. On April 15, the day
that the last bulletin ARLP015 was written, the flux dropped to 88,
which is the lowest it has been since the peak of the current solar
cycle. The last time it was this low was in October 1987, on the
rising side of the cycle. On October 3, 1987 the flux was 86, and
the next day it was 89.
Low flux values such as this mean depressed MUF, giving us poor
propagation on the higher frequencies. Look for more conditions
like this as the current cycle winds down over the next few years.
But don't expect the solar flux to hit 88 again immediately. On the
next solar rotation, the lowest values forecast are around 100.
The most disturbed periods during the past week were when the K
index hit 5, at 0600z and 0900z on April 15, and again at 0900z on
April 21. We could see more disturbed conditions around May 2 and
10. The solar flux should rise to 150 around April 30 and again on
May 6 and 7, and then drop to a low of 100 around the middle of May.
Sunspot Numbers from April 15 to 21 were 30, 42, 57, 94, 113, 157
and 147, with a mean of 91.4. 10.7 cm flux was 88.2, 90.2, 95.7,
106, 110.9, 118.9 and 119.3, with a mean of 104.2.
The path projection this week is from Seattle to Spain.
80 meters should be open from 0300z to 0600z, peaking around 0430z.
40 meters should be good from 0130z to 0630z, peaking around 0300z
to 0530z. 30 meters should be open from 2330z to 0800z, with the
best conditions around 0230z to 0600z. 20 meters should be open
from 2000z to 0830z, with marginal conditions around 0400z, and the
best conditions around 0230z and again at 0500z. 17 meters should
be open most days from 1500z to 0130z, with best conditions from
2000z to 2200z. 15 meters looks marginal over this path, but
on some days it may be open from 1730z to 0100z. 12 and 10 meters
will prove difficult, but on a few days there may be openings over
this path during daylight hours.
/EX