SB PROP @ ARL $ARLP053<br />ARLP053 Propagation de K7RA<br /><br />ZCZC AP53<br />QST de W1AW <br />Propagation Forecast Bulletin 53 ARLP053<br />From Tad Cook, K7RA<br />Seattle, WA December 23, 2004<br />To all radio amateurs <br /><br />SB PROP ARL ARLP053<br />ARLP053 Propagation de K7RA<br /><br />After passing the longest night of the year, the northern hemisphere<br />will have gradually increasing sunlight over the next six months.<br />These seasonal variations have a big effect impact on propagation.<br />As an example, using a popular propagation program to calculate a<br />path from Seattle to Cleveland on December 22 with a sunspot number<br />of 35 (average value for December 20-22), I looked at a projection<br />for the 30 meter band. 30 meters should open toward Ohio around<br />8:00 AM Seattle time, around Seattle's sunrise. Expected signals<br />should be good until sunset, when signals jump higher by 10-20 db.<br />Then the chance of an opening stays low most of the night. From<br />sunrise to sunset is 8 hours and 20 minutes.<br /><br />Running the same values two months later, there are nearly two more<br />hours of sunlight at the Seattle end. 30 meters looks good to<br />Cleveland most times of the day and night, except for a low<br />probability of an opening from after midnight until sunrise at the<br />Seattle end.<br /><br />Los Angeles sits in much more sunlight than Seattle in the dead of<br />winter, with almost 10 hours from sunrise to sunset on the solstice.<br />On December 22 the 30 meter path to Cleveland is open most hours of<br />the day and night. The possibility of an opening drops during the<br />hours of 6-9 PM LA time, and again from 2-5 AM. On February 22, LA<br />sees over 11 hours from sunrise to sunset, and 30 meters should be<br />open to Cleveland with strong signals at any time, except for a<br />brief period with lower chance of an opening just before LA sunrise.<br /><br />Jack Bock, K7ZR (SK) used to write about the ''Sufferin' Sevens'' in<br />the Totem Tabloid, the newsletter for the Western Washington DX<br />Club. He was referring to hams in Washington state and probably<br />KL7, not Arizona. Having more light really does help.<br /><br />For the past week, sunspot numbers were up and the A index was lower<br />when compared to the previous week. Average daily sunspot numbers<br />and solar flux values rose over 5 points, and the mid-latitude A<br />index was down over two points.<br /><br />For the next week, daily sunspot numbers should be moderately higher<br />and solar flux should stay above 100 until the last day of the year.<br />At that time, we can look at the average sunspot numbers for 2004,<br />and compare them with previous years. Right now it looks like the<br />average daily sunspot number for 2004 will come in about 40 points<br />lower than 2003 and over 100 points lower than 2002.<br /><br />If you would like to comment or have a tip, email the author at<br />k7raarrl.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 December 16 through 22 were 14, 40, 40, 29, 30,<br />25 and 47 with a mean of 32.1. 10.7 cm flux was 90, 89.9, 90.6, 94,<br />93.9, 101 and 98.8, with a mean of 94. Estimated planetary A<br />indices were 10, 15, 12, 4, 4, 12 and 19 with a mean of 10.9.<br />Estimated mid-latitude A indices were 8, 9, 8, 1, 2, 6 and 12, with<br />a mean of 6.6.<br />NNNN<br />/EX