SB PROP @ ARL $ARLP007<br />ARLP007 Propagation de K7RA<br /><br />ZCZC AP07<br />QST de W1AW <br />Propagation Forecast Bulletin 7 ARLP007<br />>From Tad Cook, K7RA<br />Seattle, WA February 18, 2005<br />To all radio amateurs <br /><br />SB PROP ARL ARLP007<br />ARLP007 Propagation de K7RA<br /><br />Conditions improved this week over last. The average daily sunspot<br />number rose nearly 34 points to 75.1, and the geomagnetic indices<br />were down over the week. The geomagnetic field may become more<br />active, and for February 18-20 the planetary A index is predicted at<br />20, 20 and 15. The major sunspot group affecting us this week will<br />soon move off the visible solar disk, but there is a small sunspot<br />group on the other side of the sun. Conditions should be fair to<br />good for the ARRL International DX CW Contest this weekend.<br /><br />Carl Luetzelschwab, K9LA has an interesting and useful propagation<br />column in the March 2005 issue of WorldRadio. With ionosonde data he<br />demonstrates how daily variations in solar flux have little effect<br />on the MUF. Instead, propagation is better predicted with a smoothed<br />sunspot number applied to seasonal variations.<br /><br />For instance, this afternoon when I wanted a feeling for when 15 and<br />17 meters would still be open toward various locations, it was<br />better to use W6ELprop with an average of sunspot numbers for the<br />previous five days rather than today's solar flux. You can get the<br />recent sunspot numbers from<br />
http://www.sec.noaa.gov/ftpdir/indices/DSD.txt, and download<br />W6ELprop from
http://www.qsl.net/w6elprop/.<br /><br />This afternoon I went out to the car to do some 17 meter mobile<br />work. Geomagnetic indices were low and the band was good. I had a<br />nice CW chat with KG0TS in Des Moines, Iowa, and then worked<br />9Y4/YL2GM in Tobago on SSB. Juris was in the Caribbean getting ready<br />for the DX contest from 9Y4W this weekend.<br /><br />If you would like to comment or have a tip, email the author at,<br />k7ra@arrl.net.<br /><br />For more information concerning propagation and an explanation of<br />the numbers used in this bulletin see the ARRL Technical Information<br />Service propagation page at,<br />
http://www.arrl.org/tis/info/propagation.html.<br /><br />Sunspot numbers for February 10 through 16 were 63, 73, 72, 73, 115,<br />69 and 61 with a mean of 75.1. 10.7 cm flux was 114.1, 114.1, 116.4,<br />115.5, 118.1, 121.7 and 112.8, with a mean of 116.1. Estimated<br />planetary A indices were 17, 11, 5, 4, 5, 5 and 13 with a mean of<br />8.6. Estimated mid-latitude A indices were 11, 7, 3, 2, 4, 1 and 8,<br />with a mean of 5.1.<br />NNNN<br />/EX
