The   elevation   antenna,   AS-1669/SPN-35,   is   a truncated  paraboloid-type  reflector  with  a  dual-channel feedhorn   and   a polarizer   assembly   providing monopulse-type   radiation   and   reception   of   X-band rf  pulses.  The  horizontal  shape  of  the  laminated fiberglass  reflector  is  cosecanted.  The  dual-channel feedhorn  and  polarizer  are  fixed  in  circular  polarization by  an  external  grid  device.  The  elevation  antenna  is stabilized-yoke  mounted  on  the  elevation  drive assembly   adjacent   to   the   azimuth   antenna. The elevation  drive  provides  the  required  motion  for  the elevation  antenna  and  locks  electrically  with  the  search drive  when  the  radar  set  operates  in  the  precision mode. The radar operates in three modes, final, surveil- lance,  and  simultaneous,  with  each  antenna  acting independently. In   the   final   (precision)   mode,   the azimuth antenna scans a 30-degree sector (60-degree sector  optional)  while  the  elevation  antenna  scans  a 10-degree  sector  (35-degree  sector  optional).  In  the surveillance  mode  the  azimuth  antenna  rotates  through the  full  360-degree  search  pattern  at  16  rpm  while the  elevation  antenna  scans  a  10-degree  sector.  In the  simultaneous  mode,  the  azimuth  antenna  rotates through  the  full  360-degrees  search  pattern  in 60-degree  increments  while  the  elevation  antenna  scans a  10-degree  sector. The  data  rate  in  this  mode  is approximately  16  azimuth  sweeps  and  24  elevation sweeps  every  60  seconds. The  antenna  pedestal  control  stabilizes  the  azimuth and  elevation  antennas  for  plus  or  minus  3  degrees of  pitch  and  plus  or  minus  10  degrees  of  roll. RF   SAFETY   PRECAUTIONS Although  radio  frequency  emissions  are  usually harmless, there are still certain safety precautions you should  follow  whenever  you  are  near  high-power  rf sources.   Normally,   electromagnetic   radiation   from transmission  lines  and  antennas  isn’t  strong  enough to electrocute personnel. However, it may lead to other accidents  and  can  compound  injuries.  Voltages  may be  induced  into  metal  objects  both  above  and  below ground, such as wire guys, wire cable, hand rails, and ladders.  If  you  come  into  contact  with  these  objects, you  may  receive  a  shock  or  an  rf  burn.  The  shock can cause you to jump involuntarily, to fall into nearby equipment,  or,  when  working  aloft,  to  fall  from  the elevated   work   area.   Take   care   to   ensure   that   all transmission lines or antennas are de-energized before working  on  or  near  them. When  working  aloft  aboard  ship,  be  sure  to  use a  working  aloft  chit.  This  will  ensure  that  all  radiators, not only those on your own ship but also those nearby are  secured  while  you  are  aloft. ALWAYS  obey  rf  radiation  warning  signs  and keep  a  safe  distance  from  radiating  antennas.  The six types of warning signs for rf radiation hazards are shown  in  figure  2-49. The  two  primary  safety  concerns  associated  with rf fields are rf burns and injuries caused by dielectric heating. RF  BURNS Close  or  direct  contact  with  rf  transmission  lines or antennas may result in rf burns caused by induced voltages.  These  burns  are  usually  deep,  penetrating, third-degree  burns.  To  heal  properly,  rf  burns  must heal  from  the  inside  toward  the  skin’s  surface.  Do NOT  take  rf  burns  lightly.  To  prevent  infection,  you must give proper attention to ALL rf burns, including the  small  pinhole  burns.    ALWAYS  seek  treatment for  any  rf  burn  or  shock  and  report  the  incident  to your  supervisor  so  appropriate  action  can  be  taken to  correct  the  hazard. DIELECTRIC   HEATING While the severity of rf burns may vary from minor to  major,  burns  or  other  damage  done  by  DIELEC- TRIC  HEATING  may  result  in  long-term  injury,  or even  death.  Dielectric  heating  is  the  heating  of  an insulating   material   caused   by   placing   it   in   a high-frequency  electric  field.  The  heat  results  from the rapid reversal of molecular polarization dielectric material. When a human is in an rf field, the body acts as the  dielectric.  If  the  power  in  the  rf  field  exceeds  10 milliwatts  per  centimeter,  the  individual  will  have  a noticeable  rise  in  body  temperature.  Basically,  the body  is  “cooking”  in  the  rf  field.  The  vital  organs 2-30