def band_to_frequency(band):
  """
  nominal band center frequency in GHz from band code
  """
  if   band == "L":  return 1.7
  elif band == "S":  return 2.3
  elif band == "C":  return 5.0
  elif band == "X":  return 8.45
  elif band == "Ku": return 15
  elif band == "K":  return 22
  elif band == "Ka": return 34
  elif band == "Q":  return 42
  elif band == "W":  return 90
  else: return None