[HCARC] NVIS Data

[SARA SANDSTROM]

Hi Eddie, 
  
I found a source of NVIS data you might be interested in.  It is from the NOAA Space weather Prediction Center site.  Address is http://www.swpc.noaa.gov/ftpdir/lists/iono_day/Boulder_ic .  The number you are interested in is f0F2 which is the vertical incidence highest frequency reflected back to the earth.  This particular file gives the most recent day and for Boulder gives the value for every 15 minutes.  Times are GMT.  There are a lot of other locations listed but Boulder is probably the one most likely to have data that is closest to Austin/San Antonio.  The actual NVIS frequency may be slightly higher for the 75 Miles or so that we are apart rather than vertical incidence, but the values will be close.  
  
Looking at the data for 24 October,  f0F@ drops below 7 MHz at 0115 UT at Boulder, below 3.2 MHz at 0345 UT and climbs back above 3.7 MHz at 1045 UT and above 7.1 MHz at 1415 UT.   It runs between 10 and 11 MHz between 1830 and 2300 UT .  Note that the solar flux is currently running in the 140's, 150's and 160's so it is quite high.  It won't get much better than this. 
  
As you can see, NVIS at 40 m is almost completely an afternoon event.  After local sunset, even 80 m is useless for NVIS.  I do work some Austin area stations in the evening and morning on 80 and 40 m but I'm not sure what the propagation mode is.  I use a v ertical antenna and stations I work are using either verticals or high dipoles so I t hink NVIS is not the likely mode.  
  
If you want to discuss, just send an e-mail. 
  
Kerry, K5KS 
Harper, TX