function showcredit()
{
window.alert("Script programmed by Jens T.Saetre 15082003");

//var theResponse = window.prompt("Welcome?","Enter your name here.");
}



function main()
{
var Offset,Width,Height,Elevation
Width=1*document.Antenna.Width.value;
Height=1*document.Antenna.Height.value;
Elevation=1*document.Antenna.Elevation.value;
document.Antenna.Efficiency.value=formatvalue((Width/Height)*AntennaEfficiency(), 5);
document.Antenna.OffsetAngle.value=formatvalue(Math.acos(Width/Height)*(180/Math.PI), 5);
document.Antenna.measured.value=formatvalue((90-(  (Math.acos(Width/Height)*(180/Math.PI)) - Elevation))   , 5);
}


function log10(X)
{
return( Math.log(X)/Math.log(10)  );
// works OK !
}


function AntennaEfficiency()
{
var AntennaEfficiency,RxFrequency,Gain,AntennaDiameter,Factor
RxFrequency=1*document.Antenna.Frequency.value;
Gain=1*document.Antenna.Gain.value;
AntennaDiameter=1*document.Antenna.Width.value ;
AntennaEfficiency=100* Math.pow(10,((-20*log10(RxFrequency/1000) -20*log10(AntennaDiameter)-20.4  + Gain)/10));
return(AntennaEfficiency);
}












function formatvalue(input, rsize) // Desimal avrunding
  {
   var invalid = "**************************";
   var nines = "999999999999999999999999";
   var strin = "" + input;
   var fltin = parseFloat(strin);
   if (strin.length <= rsize) return strin;
   if (strin.indexOf("e") != -1 ||
       fltin > parseFloat(nines.substring(0,rsize)+".4"))
      return invalid.substring(0, rsize);
   var rounded = "" + (fltin + (fltin - parseFloat(strin.substring(0, rsize))));
   return rounded.substring(0, rsize);
}