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ARRL Propagation Bulletin ARLP026 (2003)

ARLP026 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 26  ARLP026
From Tad Cook, K7RA
Seattle, WA  June 27, 2003
To all radio amateurs 

ARLP026 Propagation de K7RA

This week had somewhat quieter geomagnetic conditions compared to
the previous week, but average daily solar flux was down a bit and
average daily sunspot numbers remained about the same. Recent
projections anticipate no truly quiet periods ahead.

ARRL Field Day is this weekend, and I wish the geomagnetic
conditions could be better. The predicted planetary A index for
Friday through Monday is 20, 25, 20 and 20. Although an A index of
25 for Saturday doesn't look very promising, this prediction is made
several days prior, and like weather forecasts, the real conditions
could be different. In addition, a planetary A index of 20 or 25
doesn't guarantee a radio blackout on the high frequencies.

Just to run some numbers for this weekend, using W6ELprop (download
free from for Saturday with a path
from California to Ohio, a solar flux of 125 and K index of 4, we
see 20-meters opening on Saturday morning before the start of Field
Day and continuing a good path through the day. Around 2330z the
path may be unreliable, then it comes back a lot stronger at 0100z.
This is just as 40-meters is starting to open. Both bands stay
strong through the night until local sunrise in California.
80-meters opens after sunset in California, and fades after sunrise
in Ohio. The path opens on 20-meters around 1430z.

David Moore of Morro Bay, California wrote in with a tip about an
interesting article that details some new findings regarding the
mechanics of the solar cycle. The article reports research
suggesting slowly moving circulating currents of compressed gasses
125,000 miles into the sun's interior influence the production of
sunspots. The article also says that the speed of these circulating
currents of gasses varies from cycle to cycle, and the fast
circulation in the last cycle suggests the next cycle should be
strong, peaking around 7 or 8 years from now. You can read the
article at

Still more reports arrived about the VHF openings around June 17.
Jake Groenhof, N0LX wrote to say he was on Mount Evans in Colorado
and using one half watt on 2-meter SSB when he worked a station 850
miles away in California. He went up to 5 watts and worked five more
Californians. He has a web page detailing this at

Ward Silver, N0AX wrote to say that the description in last week's
bulletin of the A index being linear was incorrect. The related K
index is logarithmic, but the A index is a larger scale, and not

Sunspot numbers for June 19 through 25 were 108, 121, 118, 94, 104,
131, and 115, with a mean of 113. 10.7 cm flux was 122.9, 116.9,
115, 110.2, 113.5, 114.5, and 116.3, with a mean of 115.6. Estimated
planetary A indices were 18, 12, 23, 16, 20, 31, and 19, with a mean
of 19.9.


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