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TRANSMIT DATA SIGNAL PATH.  Continued
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TM-11-5820-890-30-5 Ground Non-Icom Radio Sets Consisting of: Receiver-Transmitter Radio RT-1439/VRC (NSN 5896-01-195-0827) Manual
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Figure 2-10. FH Block Diagram


TM 11-5820-890-30-5 2-14. PRIMARY CONTROL SIGNALS.  Continued When  the  RT  is  transmitting,  the  T/R  line  is  set  to  logic  1  by  the  control  module.  It  checks  the  MED  PWR,  HI PWR/M,  and  HI  PWR/V  lines  from  the  RF  switch.  If  none  are  at  logic  1,  the  RT  RF  output  is  set  for  low  power operation. The SIG display circuit uses the RF DETECT, RF PWR A, RF PWR B, HI PWR XMT, PA PWR LVL, and T/R lines  during  transmit  to  drive  the  display.  The  SIG  STR  RCV  signal  is  used  during  receive. During retransmit operation, all of the RXMT connector I/O is controlled by the switching module. See paragraph 2-17  for  a  description  of  retransmit  operations. The  keyboard  display  is  controlled  by  the  control  module.  The  SERIAL  DATA,  DISPLAY  CLK,  and  DISP  EN-N provide the information needed by the display drivers. A DISPLAY INHIBIT line is used by the remote l/O to turn the display   off   during   remote   operation. The keyboard is made up of 16 switches (keys). They are arranged in a four-by-four switch matrix. The control module checks the X and Y lines to see if a key has been pressed. The Y lines (rows) are normally at logic 1. The X line (columns) are normally at logic 0. When a key is pressed, the Y line will be pulled to logic 0. The X line will be  pulled  high  (to  about  6  V  dc). 2-15. FREQUENCY HOPPING OPERATIONS. The  programming  for  FH  operation  is  stored  in  the  ECCM  module  ROM.  The  control  module  executes  these commands  to  control  the  RT  while  in  FH. Received FH signals are digital signals. The switching module digital processing produces bit synchronized data (BS  DATA).  See  figure  2-10.  BS  DATA  is  the  RCV  FH  signal  synchronized  with  the  internal  RT  clocks  and converted  to  RT  digital  signal  levels.  BS  DATA  goes  to  the  ECCM  module  interleave  circuits.  The  interleaver removes    synchronization    and    frequency    hopping    information    that    is    embedded    in    the    signal.    After deinterleaving, the signal is reclocked at a 16 kb/s rate. It is now the FH DATA signal. In RCV DATA mode, FH DATA is routed to the switching module. When receiving audio, FH DATA is converted back to an analog signal by the continuously variable slope detector (CVSD) in the ECCM module. The RCV FH AUDIO output is also routed to the   switching   module. Two signals are required by the ECCM module during FH transmit. They are BS DATA and XMT PT AUDIO. BS DATA goes directly to the interleave. It is interleaved with the synchronization and FH information needed by the receiving RT to coordinate communications. The CVSD converts XMT PT AUDIO to a 16 kb/s digital signal output as CVSD DATA to the interleave. It too is interleaved with data, reclocked to 20 kb/s, and output on the FH DATA line  to  the  switching  module. The   interleave   supplies   the   control   and   data   signals   needed   by   the   time   sync/correlator.   The   correlator’s function  is  to  synchronize  the  operation  of  the  RT  and  the  ECCM  module.  It  manipulates  control  signal  outputs such   as   HOP   TIME   and   SYNC.   These   and   others   control   RT   operations   in   FH   mode.   They   shut   down reception/transmission  during  frequency  shifts,  provide  the  next  frequency  to  the  control  module  (via  the  data and  address  buses),  and  supply  clocking  for  the  ECCM  module. The  ECCM  module  is  also  responsible  for:  storage  of  the  FH  operation  programming,  generation  of  random numbers   for   hopping   frequency   selection,   and   processing   and   storage   of   FILL   data.   The   RT   chooses   the frequencies  in  FH  by  pseudorandom  number  generation.  The  TRANSEC  variable,  FH  sync  time,  and  net  ID number are used to select the next frequency. The control module uses the hopset and lockout set to create a look-up table in memory of frequencies for the net. The ECCM module picks one of these frequencies from the table.  The  result  is  passed  to  the  control  module  via  the  data  bus.  The  control  module  informs  the  rest  of  the modules  of  the  frequency  selected  by  the  SERIAL  DATA  line. 2-18


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