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ARRL Propagation Bulletin ARLP010 (1998)

ARLP010 Propagation de K7VVV

Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7VVV
Seattle, WA  March 6, 1998
To all radio amateurs

ARLP010 Propagation de K7VVV

Average sunspot numbers were slightly higher and average solar flux
was only a little lower last week.  The average solar flux for the
previous 90 days declined one point to 95, and flux values were
above that level for three days out of the week.

KC7ZMV wrote with an interesting observation about the comparison of
the previous two solar cycles with the current cycle on the web at, as mentioned in the last
propagation bulletin, ARLP009.  Jim noted that the website claims
that the current cycle began in May 1996, but he has read elsewhere
that October 1996 is a better date.  If one accepts the later date,
then perhaps the current cycle isn't really lagging the other

NOAA has the announcement about the revised date at  Looking at the charts at the
cycle comparison site, it isn't clear whether the graphs are really
drawn from the beginning of each cycle or from the minimum.  Since
they are moving averages, the trend line lags behind the current
data about six months.

If one looks out beyond the trend line on the current cycle it
appears that the data has leveled out, and this is born out in the
current monthly average just calculated.  The monthly average solar
flux values for November through January were 99.5, 98.7 and 93.4,
and in February the average flux was 93.4, precisely what it was in
January.  We can hope for better, but it still looks like solar
activity is lagging.

Conditions should be fairly good for the ARRL International DX SSB
Contest this weekend, with predicted solar flux for Friday through
Sunday at 94, 92 and 90.  No geomagnetic disturbances are foreseen.
Solar flux should increase after the weekend, rising above 100
around March 13 and dipping back into the high nineties after March

Sunspot Numbers for February 26 through March 4 were 69, 78, 60, 93,
105, 56 and 55 with a mean of 73.7.  10.7 cm flux was 92.7, 90.3,
94, 98.3, 91.5, 96.6 and 101.7, with a mean of 95, and estimated
planetary A indices were 3, 4, 12, 12, 14, 4, and 8, with a mean of


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