function setModelType(f,option_no) {
  var i=0;
  
  // clear selection options	 
  while (i < f.category.length) {
    f.category.options[i] = null;
    i++;
  }

    f.category.options[0] = new Option("Choose Splitter/Combiner Type","psc_coax_hpcs.html");

  if (option_no == "lt") {
    f.category.length = 5;
    f.category.options[1] = new Option("2 Way, 0 Degree","psc_sm_2_0_ltcc.html");
    f.category.options[2] = new Option("2 Way, 90 Degree","psc_sm_2_90_ltcc.html");
    f.category.options[3] = new Option("3 Way, 0 Degree","psc_sm_3_0_ltcc.html");
    f.category.options[4] = new Option("4 Way, 0 Degree","psc_sm_4_0_ltcc.html");
  }
  else if (option_no == "coax") {i
    f.category.length = 17;
    f.category.options[1] = new Option("High Power, 2,3,4,5,6 & 8 Way","psc_coax_hpcs.html");
    f.category.options[2] = new Option("2 Way, 0 Degree","psc_coax_2_0.html");
    f.category.options[3] = new Option("2 Way, 0 Degree, Resistive","psc_coax_2_0_resistive.html");
    f.category.options[4] = new Option("2 Way, 90 Degree","psc_coax_2_90.html");
    f.category.options[5] = new Option("2 Way, 180 Degree","psc_coax_2_180.html");
    f.category.options[6] = new Option("3 Way, 0 Degree","psc_coax_3_0.html");
    f.category.options[7] = new Option("4 Way, 0 Degree","psc_coax_4_0.html");
    f.category.options[8] = new Option("5 Way, 0 Degree","psc_coax_5_0.html");
    f.category.options[9] = new Option("6 Way, 0 Degree","psc_coax_6_0.html");
    f.category.options[10] = new Option("8 Way, 0 Degree","psc_coax_8_0.html");
    f.category.options[11] = new Option("10 Way, 0 Degree","psc_coax_10_0.html");
    f.category.options[12] = new Option("12 Way, 0 Degree","psc_coax_12_0.html");
    f.category.options[13] = new Option("16 Way, 0 Degree","psc_coax_16_0.html");
    f.category.options[14] = new Option("24 Way, 0 Degree","psc_coax_24_0.html");
    f.category.options[15] = new Option("48 Way, 0 Degree","psc_coax_48_0.html");
  }
  else if (option_no == "pi") {
    f.category.length = 14;
    f.category.options[1] = new Option("2 Way, 0 Degree","psc_pic_2_0.html");
    f.category.options[2] = new Option("2 Way, 0 Degree, Resistive","psc_pic_2_0_resistive.html");
    f.category.options[3] = new Option("2 Way, 90 Degree","psc_pic_2_90.html");
    f.category.options[4] = new Option("2 Way, 180 Degree","psc_pic_2_180.html");
    f.category.options[5] = new Option("2 Way, 0/180 Degree","psc_pic_2_0_180.html");
    f.category.options[6] = new Option("3 Way, 0 Degree","psc_pic_3_0.html");
    f.category.options[7] = new Option("4 Way, 0 Degree","psc_pic_4_0.html");
    f.category.options[8] = new Option("5 Way, 0 Degree","psc_pic_5_0.html");
    f.category.options[9] = new Option("6 Way, 0 Degree","psc_pic_6_0.html");
    f.category.options[10] = new Option("8 Way, 0 Degree","psc_pic_8_0.html");
    f.category.options[11] = new Option("9 Way, 0 Degree","psc_pic_9_0.html");
    f.category.options[12] = new Option("10 Way, 0 Degree","psc_pic_10_0.html");
    f.category.options[13] = new Option("12 Way, 0 Degree","psc_pic_12_0.html");
  }
  else if (option_no == "sm") {
    f.category.length = 13;
    f.category.options[1] = new Option("2 Way, 0 Degree","psc_sm_2_0.html");
    f.category.options[2] = new Option("2 Way, 90 Degree","psc_sm_2_90.html");
    f.category.options[3] = new Option("2 Way, 180 Degree","psc_sm_2_180.html");
    f.category.options[4] = new Option("2 Way, 0/180 Degree","psc_sm_2_0_180.html");
    f.category.options[5] = new Option("3 Way, 0 Degree","psc_sm_3_0.html");
    f.category.options[6] = new Option("4 Way, 0 Degree","psc_sm_4_0.html");
    f.category.options[7] = new Option("4 Way, Quadrifilar","psc_sm_quadrifilar.html");
    f.category.options[8] = new Option("5 Way, 0 Degree","psc_sm_5_0.html");
    f.category.options[9] = new Option("6 Way, 0 Degree","psc_sm_6_0.html");
    f.category.options[10] = new Option("8 Way, 0 Degree","psc_sm_8_0.html");
    f.category.options[11] = new Option("12 Way, 0 Degree","psc_sm_12_0.html");
    f.category.options[12] = new Option("16 Way, 0 Degree","psc_sm_16_0.html");
  }
}