[SFDXA] ARRL Propagation Statement

[Bill Marx]

> Disturbed conditions triggered by a continuous solar wind stream
> appear to go on and on, week after week, seemingly without end.
> Nice quiet conditions would result from a daily A index of 10 or
> lower. Average daily conditions near that level haven't been
> reported since the week of February 20-26 when the daily average A
> index was 11.1, or January 9-15 when it was 9.1.
> 
> Conventional wisdom says that disturbed conditions occur more often
> when the solar cycle has passed the peak and is headed down, and
> recent experience seems to bear this out. Recent forecasts for daily
> solar flux and planetary A index don't predict a daily A index below
> 10 until May 31.
> 
> A plot from Jim Secan and Northwest Research Associates shows the
> decline of the solar cycle over the past year at
> http://www.nwra-az.com/spawx/ssne-year.html. The latest projection
> has solar flux rising over the next few days to 110 on Saturday, May
> 17, 120 on Sunday and 125 on Monday. The daily planetary A index
> projection shows an unsettled 15 thought the weekend, rising to 20
> on Monday.
> 
> The solar flux and sunspot numbers were lower this week than last,
> but the A index was higher. The average daily sunspot number dropped
> around 100 points from 146 to 46.4, and daily solar flux was down
> over 40 points to 95.5. Average daily A index rose from 20.7 to
> 29.3.
> 
> Last week we mentioned Scott Craig, WA4TTK and his solar plotting
> utility freeware available at
> http://www.craigcentral.com/mystuff.asp. Scott says he usually gets
> 100-150 visits per day to his web page, but last Friday when the
> bulletin came out he got 270, and Saturday it was 393.
> 
> The announcement this week about the new 60-meter band brings
> speculation about propagation characteristics. Initially this will
> probably be used just for domestic communications, since no other
> country has adopted these frequencies for the amateur service. A
> quick look with a propagation prediction program shows the band
> opening and closing at hours somewhere between the 75 and 40-meter
> bands.
> 
> With W6ELprop looking from Seattle to Atlanta, assuming that the
> band is legal one month from now and the sunspot number is around
> 100, 60-meters seems to open a half hour earlier than 75- meters and
> close a half hour later. Signal strengths during the peak hours,
> which for the above parameters are from 0500-1000z, are between the
> levels for 40 and 75-meters as well. A similar projection for
> mid-September from California to Ohio shows similar characteristics,
> although with more hours of darkness the openings are longer.
> 
> Mark Roberts, KD5SMF sent an email this week asking for a source for
> the numbers used in the W6ELprop software, a free windows-based
> program that can be downloaded at http://www.qsl.net/w6elprop/. I
> wrote to him and said that it is probably better to take an average
> of several days sunspot numbers and use that instead of the latest
> daily solar flux. You can get both values at
> http://sec.noaa.gov/ftpdir/latest/DSD.txt, and several daily K
> indices from http://sec.noaa.gov/ftpdir/latest/DGD.txt.
> 
> The latest mid-latitude K index is on WWV at 18 minutes after each
> hour, or you can get the WWV message on the telephone at
> 303-497-3235. The text of that hourly message is available on the
> web at http://sec.noaa.gov/ftpdir/latest/wwv.txt.
> 
> For more information on propagation and an explanation of the
> numbers used in this bulletin see the Propagation page on the ARRL
> Web site at http://www.arrl.org/tis/info/propagation.html. You can
> write to the author of this bulletin at k7ra@arrl.net.
> 
> Sunspot numbers for May 8 through 14 were 33, 23, 22, 47, 66, 59,
> and 75, with a mean of 46.4. 10.7 cm flux was 100.9, 97.1, 92.7,
> 91.5, 93.9, 96.1, and 96.3 with a mean of 95.5. Estimated planetary
> A indices were 30, 29, 43, 31, 18, 27, and 27, with a mean of 29.3.