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FRAME  CNT
PHASE  ERROR  (DEGREES)

Fire Controlman Volume 06-Digital Communications
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Figure  3-12.—The  LMS-11  PU  Display  mode. REL 605.—  This  column  indicates  the  relative power of the 605-Hz tone with respect to the average power of the 15 data tones, measured in dB. It should be +6 dB. VAR DATA.— This is the variation of power in the data tones in dB. The relative power of each of the data tones, with respect to the average power of the  data  tones,  is  determined.  The  variation  is  the difference between the maximum and the minimum. Under  ideal  conditions,  the  variation  is  zero.  The TADIL  A  specification  for  maximum  variation  is  1.5 dB l PHASE ERR M.—  This is the mean, or average, phase  error  of  the  data  tones.  The  intelligence  is stored in the data tones by use of the phase differences that  are  odd  multiples  of  45  degrees.  If  the  phase difference  of  a  data  frame  is  50  degrees  when  the expected  difference  is  45  degrees,  the  error  is 5 degrees. The phase errors for each tone are added up, and after the specified number of cycles, the sum for each tone is divided by the number of frames to obtain the mean phase error for each tone. The mean phase  error  for  all  15  tones  is  then  summed  and divided by 15 to obtain the value displayed. PHASE  ERROR  SD.—  This  is  the  standard deviation of the phase error in all 15 tones. RFE/DS.—  This is the radio frequency error, or Doppler  shift,  measured  in  Hertz.  If  the  Doppler correction   was   enabled   during   the   LMS-11 initialization, the value is color-coded green. If the Doppler correction is turned off, this value is color- coded  cyan. NCT.—  This is the net cycle time, as measured from phase reference frame to phase reference frame, of the reporting unit. Note that this measure of net cycle time is different from that used in other NCT calculations. PU Display The  PU  display  shows  detailed  information  about the  signal  received  from  the  specified  PU.  The  PU display can operate in Broadcast, Short Broadcast, and Roll Call modes. In Broadcast and Short Broadcast, the  display  is  updated  after  every  transmission.  In  the Roll  Call  mode,  the  display  is  updated  after  the specified number of net cycles or 200 transmissions, 3-15






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