function inRange(freq) {
  var OK = ((freq >= 129.9) && (freq <= 170.65));
  if (!OK)
    alert("Please enter a number between 129.90 and 170.65 GHz");
  return OK;
}

function toRealCenterFreq(freq) {
  freq -= 129.65;
  freq /= .55;
  freq = Math.round(freq);
  freq = 129.65 + freq*.55;
  if (freq < 130.2) freq = 130.2;
  if (freq > 170.35) freq = 170.35;
  return freq;
}