ARLP019 Propagation de K7RA:
May 7, 2004

Propagation Forecast Bulletin 19 ARLP019
From Tad Cook, K7RA
Seattle, WA May 7, 2004
To all radio amateurs

ARLP019 Propagation de K7RA

Thanks to Carl Luetzelschwab, K9LA for writing last week's propagation forecast bulletin.

Your regular author was without power or other overhead utilities from Tuesday through Saturday after a localized squall in the city took down a large tree. This yanked out the electrical service mast, and all that plus the breaker panel had to be upgraded. Urban camping for several days made us really appreciate cheap, plentiful electric power.

Carl mentioned last week that the solar cycle continues to decline. Average daily sunspot and solar flux further dropped from last week to this week, with average daily sunspot numbers down by nearly 5 points. Average sunspot numbers for the past two weeks were 52.7 and 48.1. Compare this with the last week in April and first week in May in 2003, when average daily sunspot numbers were 185.1 and 146. However, three years from now the cycle should begin to turn up again. Of course, at that time (Spring 2007), sunspot counts at the bottom of the cycle will be much lower than now.

For the short term we can expect quiet geomagnetic conditions, good for HF propagation. Daily solar flux values are expected to stay below 100 until around May 18. Geomagnetic conditions should stay quiet until May 20. Currently there are two small sunspots facing earth, and helioseismic holography reveals no substantial sunspots on the sun's far side.

Quiet conditions seem favorable for this weekend's CQ-M International DX Contest, although scant sunspots will likely make 20 meters the best overall band for worldwide DX, with less long distance propagation on 15 meters.

For more information concerning propagation and an explanation of the numbers used in this bulletin see the ARRL Technical Information Service propagation page at,

If you use Scott Craig's Solar Data Plotting Utility, you'll need to edit this bulletin into two versions for automatic insertion of data. Just make one version with last week's numbers, and the other file with this week's, so you don't confuse the software.

Sunspot numbers for April 22 through 28 were 90, 63, 64, 45, 47, 28 and 32 with a mean of 52.7. 10.7 cm flux was 117.1, 115.3, 111.6, 107.1, 99.6, 95.1 and 89.5, with a mean of 105. Estimated planetary A indices were 4, 20, 11, 12, 7, 5 and 8, with a mean of 9.6. Estimated mid-latitude A indices were 5, 34, 17, 17, 5, 2 and 7, with a mean of 12.4.

Sunspot numbers for April 29 through May 5 were 25, 46, 65, 41, 50, 63 and 47 with a mean of 48.1. 10.7 cm flux was 88.5, 89.4, 94.2, 97.5, 91.3, 87.4 and 88.5, with a mean of 91. Estimated planetary A indices were 4, 12, 13, 6, 7, 10 and 13, with a mean of 9.3. Estimated mid-latitude A indices were 3, 9, 8, 4, 6, 6 and 12, with a mean of 6.9.