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ARRL Propagation Bulletin ARLP032 (2002)

ARLP032 Propagation de K7VVV

QST de W1AW  
Propagation Forecast Bulletin 32  ARLP032
From Tad Cook, K7VVV
Seattle, WA  August 2, 2002
To all radio amateurs 

ARLP032 Propagation de K7VVV

Sunspots keep growing and growing, and one wonders if the peak of
the solar cycle has really passed. With sunspot numbers over 300
this week, it almost seems like a third peak in a cycle with a
double peak so far. Sunspot numbers peaked on Saturday at 323, the
highest number since March 2001. The mean daily sunspot numbers for
the week were 122 points higher than the previous week. Average
daily solar flux was up by nearly 39 points.

Average daily sunspot numbers for all of July were 183.5. This is
much higher than June, which was 146, but not as high as May's
average, at 204.1. Average daily solar flux for July was 174.4,
higher than then 148.7 for June and around the same as May's 178.4.

Over the next few days solar flux values should decline a bit.
Solar flux predicted for Friday through Monday is 185, 180, 170 and
165. Current helioseismic readings suggest several active regions on
the sun's far side, so more excitement may be in store.

There is the possibility of aurora on Friday morning. The predicted
planetary A index for Friday through Monday is 15, 10, 12 and 10.

N4KG sent some observations on summertime propagation to

"MUF's rise very SLOWLY during summer. This means the Low Bands may
stay open to the West quite a bit longer past sunrise. One summer I
heard FR5FD on 75-meters long path 90 minutes past my sunrise.

"I noted that VK0IR made around 80% of their Midwest USA QSOs AFTER
their sunrise (in spite of early protestations that 'the sun is up,
too late'). Similarly, VP8GEO/VP8THU worked Northern Japan just
before JA sunset on 80-meters and AFTER sunrise in VP8 with DAYLIGHT
at BOTH ENDS of the path. This means the High Bands will open LATER
than usual and stay open later than usual. Typically, 20-meters is
better at night due to lower absorption than during daylight hours
due to increased D layer absorption when the sun is up.

"17-meters offers EXCELLENT worldwide propagation during summer,
often both during day and night.

"Typically, 15-meters is open to JA/Asia in our mornings and to
Europe in our afternoons, opposite to typical openings in fall,
winter, spring.

"12-meters offers some surprising nighttime openings during summer,
mimicking 15-meters more closely than 10-meters. Often the MUF seems
to ride just above 25 MHz. I have worked several Middle East DX
stations from Alabama AFTER my sunset, on an ALL DARK Path during
summer months.

"Summertime MUF's peak around 20 to 30 MHz at high sunspot levels,
and 18 to 24 MHz during low sunspot levels, depending on path and
time. This means that 10-meters can be quite marginal, especially on
polar and near polar paths."

Sunspot numbers for July 25 through 31 were 299, 319, 323, 300, 304,
297 and 265, with a mean of 301. 10.7 cm flux was 217.7, 241.5,
230.8, 238.8, 234, 227.2, and 208.5, with a mean of 228.4.
Estimated planetary A indices were 13, 17, 19, 12, 11, 8, and 9,
with a mean of 12.7.


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