SB PROP @ ARL $ARLP041   
   ARLP041 Propagation de K7RA   
      
   ZCZC AP41   
   QST de W1AW     
   Propagation Forecast Bulletin 41  ARLP041   
   From Tad Cook, K7RA   
   Seattle, WA  October 15, 2010   
   To all radio amateurs    
      
   SB PROP ARL ARLP041   
   ARLP041 Propagation de K7RA   
      
   Solar activity dropped again this week, although it is now gradually   
   strengthening.  Average daily sunspot numbers declined nearly 16   
   points to 11.7, and average daily solar flux dropped over five   
   points to 75.8.  Over the next two weeks solar flux is expected to   
   gradually increase, from 80 on October 15-16, 82 on October 17, 84   
   on October 18-22, 80 on October 23-25, and 85 on October 26-29.   
      
   The reporting week (the data at the end of this bulletin) runs   
   through Wednesday, October 13, and on Thursday, October 14 the   
   sunspot number rose from 24 to 34, and solar flux increased from   
   78.1 to 80.4.   
      
   The increase is expected from sunspot group 1112, emerging on   
   October 9, and group 1113, which appeared on October 13 rotating   
   over the eastern limb.  On October 14 new sunspot group 1114   
   appeared.  The STEREO mission at http://stereo.gsfc.nasa.gov shows a   
   series of magnetically active areas on our Sun's far side, which   
   will gradually rotate into view.   
      
   A very rough estimate of the transit time involved can be made by   
   assuming that a full rotation of the Sun is about 27.5 days.  Each   
   of those 12 longitudinal divisions on the rotating solar globe at   
   the STEREO site therefore each represent approximately 55 hours, or   
   about 2.29 days.  This can be used as a rough guide to the time it   
   takes for any area of interest to move over the eastern horizon.   
      
   Geomagnetic activity is expected to be stable, with planetary A   
   index moving between five and eight.  Predicted planetary A index is   
   7 on October 15, 8 on October 16-17, 5 on October 18, 7 on October   
   19-20, 5 on October 21-23, 8 on October 24-25, and 5 on October   
   26-29.   
      
   The Geomagnetic Department of Geophysical Institute Prague predicts   
   quiet conditions on October 15, quiet to unsettled October 16, quiet   
   October 17-20, and quiet to unsettled again on October 21.   
      
   Note the solar flux and A index data in the first and fifth   
   paragraphs is updated from similar data in yesterday's ARRL Letter.   
   You can see daily updates of this predicted data at   
   http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html.   
      
   Over the past week the most active geomagnetic day was Monday,   
   October 11, when the planetary A index was 20 and the planetary K   
   index went as high as 5.  Alaska's College A index was 49, based on   
   a College K index as high as 7.  This activity was pushed by a   
   strong solar wind.   
      
   There is an interesting and educational web page devoted to   
   heliophysics from the University Corporation for Atmospheric   
   Research in Boulder, Colorado.  See it at   
   http://www.vsp.ucar.edu/Heliophysics.   
      
   Richard Dowty, W7EET of St. Paul, Oregon isn't sure what to do with   
   the data presented in this bulletin.  He would rather see reports   
   that predict the MUF for the next week, tell him which bands will be   
   good or bad, and information of a more practical nature.   
      
   One problem with this is that MUF (Maximum Usable Frequency) is   
   different for different paths and at different times.  Generally MUF   
   should be higher when there are more sunspots.  We could make very   
   general statements such as "West coast stations should be able to   
   hear Japan on 20 meters from 2000-0230z and again at 0400-0430z,   
   with best signals from 2030-0030z, and 17 meters at 2130-0130z," but   
   that projection was actually done for Seattle.   
      
   A similar prediction for San Diego (two extremes) should say 20   
   meters to Japan from 2030-0330z, with signals 5-10 dB lower than the   
   path from Seattle, and 17 meters from 2100-0300z.  One could pick a   
   mid-point, such as around Red Bluff or Garberville, California, but   
   this produces a third set of data that doesn't really apply to the   
   north and south west coast extremes.   
      
   Years ago this bulletin would pick some point somewhere in North   
   America, and make projections toward different continents.  An   
   example is in Propagation Forecast Bulletin ARLP016 from 1999, which   
   you can see in the archive of propagation bulletins at   
   http://www.arrl.org/w1aw-bulletins-archive/ARLP016/1999.  This sort   
   of information was very popular, but the bulletin wasn't big enough   
   to handle all of the permutations of predictions for many locations   
   to many other locations.   
      
   But now we have some good free tools for doing this, such as   
   W6ELprop, which you can download at http://www.qsl.net/w6elprop.   
   This way you can see what likely propagation might be from your   
   location to anywhere else, and this works better than reading a   
   generalization in this bulletin.  Another approach is to look at the   
   monthly propagation charts linked toward the end of this bulletin.   
      
   Propagation programs are designed to use the projected smoothed   
   sunspot number for the month, which you can find in about every   
   fourth issue of the Preliminary Report and Forecast at   
   http://www.swpc.noaa.gov/weekly/index.html.  For example, if you   
   look in issue 1831, on page 10 it shows a predicted smoothed sunspot   
   number for October 2010 of 33.  The smoothed number is actually an   
   average of monthly sunspot numbers for one year, six months forward   
   and six months back, so half the data that goes into this average is   
   the predicted data for the next six months, while the rest is the   
   record of sunspot numbers for the last six months.   
      
   Propagation programs then make a prediction that basically says half   
   the time conditions will be better than this value, and half the   
   time worse.   
      
   W6ELprop can handle either sunspot numbers or solar flux, and for a   
   more recent set of data some have suggested just averaging the past   
   five days of solar flux from   
   http://www.swpc.noaa.gov/ftpdir/indices/DSD.txt and using that   
   number.  W6ELprop also uses K index, and you can get the most recent   
   mid-latitude K index from   
   http://www.swpc.noaa.gov/ftpdir/indices/DGD.txt.  But no propagation   
   program is designed to make predictions based on daily fluctuations   
   of either solar flux or sunspot number.   
      
   To find the latitude/longitude coordinates for you location, just go   
   to http://maps.google.com and enter an address.  In this example, I   
   will use 2832 SE Indiana Ave, Topeka, KS, and click "Search Maps."   
   Just above the upper right corner of the map click on Link and hit   
   Ctrl-C to copy the link displayed, then paste it into Notepad or   
   some other editor by hitting Ctrl-V.   
      
   Find the address in the link you've just pasted, and note that the   
   coordinates are just to the right, listing latitude first, longitude   
   second.  In this case it is 39.015909 and -95.660564, which can be   
   expressed as 39.02 or 39.016 degrees north latitude, and 95.66 or   
   95.661 degrees west longitude.  Note the convention is for longitude   
   to be expressed in degrees east, so west longitude appears as a   
   negative number.  W6ELprop uses the opposite convention, so west   
   longitude is a positive number.   
      
   You can use this method to find coordinates for any location of   
   interest, and enter it into the atlas portion of W6ELprop for future   
   reference.   
      
   For a good tutorial, check the link toward the end of this bulletin   
   for http://arrl.org/propagation-of-rf-signals and look for the title   
   "An Introductory Tutorial to W6ELprop."   
      
   In closing, check the November 2010 issue of QST on page 30 for an   
   article about using WSPR for studying propagation paths.   
      
   If you would like to make a comment or have a tip for our readers,   
   email the author at, k7ra@arrl.net.   
      
   For more information concerning radio propagation, see the ARRL   
   Technical Information Service web page at   
   http://arrl.org/propagation-of-rf-signals. For an explanation of the   
   numbers used in this bulletin, see   
   http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past   
   propagation bulletins is at   
   http://arrl.org/w1aw-bulletins-archive-propagation.  Find more good   
   information and tutorials on propagation at   
   http://mysite.ncnetwork.net/k9la/index.html.   
      
   Monthly propagation charts between four USA regions and twelve   
   overseas locations are at http://arrl.org/propagation.   
      
   Instructions for starting or ending email distribution of ARRL   
   bulletins are at http://arrl.org/bulletins.   
      
   Sunspot numbers for October 7 through 13 were 0, 11, 12, 13, 11, 11,   
   and 24, with a mean of 11.7. 10.7 cm flux was 75.1, 74.9, 76.4,   
   75.9, 75.3, 75.2 and 78.1 with a mean of 75.8. Estimated planetary A   
   indices were 4, 4, 4, 2, 20, 10 and 4 with a mean of 6.9. Estimated   
   mid-latitude A indices were 2, 3, 3, 1, 10, 7 and 3 with a mean of   
   4.1.   
   NNNN   
   /EX   
   .   
      
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