TM 1-1510-225-10 3-3 microphone  to  tune  the  antenna  coupler.    If  channel programming is required, it is necessary to activate the program mode. With the  FREQ  /  CHAN button in  CHAN, use a pencil or other pointed object to push the  PGM button in.  The letters PGM will appear in the lower part of the display   window   and  the  system  will  remain  in  the program mode until the  PGM button is pressed again.   Switch is alternate action: push-on, push-off. (a)  Receive Only. 1.     Stow   the   cursor   if   a   frequency digit is flashing. 2.     Channel – Select. 3.     Mode – Set (LSB, USB, or AM). 4.     Frequency     –     Set     as     desired.   Refer to frequency tuning. 5.     Push    and    release    STO    button once. TX  will  flash  in  the  display  window.    A  receive only frequency is being set, the flashing TX should be ignored. If  another  channel  is  to  be  set,  the  cursor  must be stowed before a new channel can be selected.  Use the smaller concentric knob to select the channel and repeat the steps for selecting a new frequency. 6.     To  return  to  an  operating  mode, push the PGM button. (b)  Simplex.      Setting   a   channel   up   for simplex  operation  (receive  and  transmit  on  the  same frequency). 1.     FREQ / CHAN Button  – In (Cursor stowed). 2.     PGM Button – In (PGM displayed). 3.     Channel – Select. 4.     Mode – Set (LSB, USB or AM). 5.     Frequency     –     Set     as     desired.   Refer to frequency tuning. 6.     STO button   –  Push  and  release twice. The   first   press   of   the   STO   button   stores   the frequency in the receive position and the second press stores  the  same  frequency  in  the  transmit  position.   The second push also stores the cursor. If another channel is to be reset, use the smaller concentric  knob  to  select  the  channel  and  repeat  the steps  for  selecting  a  new  frequency.    The  cursor  was automatically    stowed.        To    return    to    one    of    the operating modes, push the PGM button again. (c)  Semi-Duplex.    Setting  a  channel  for semi-duplex  (transmit  on  one  frequency  and  receive on another). 1.     Channel – Select. 2.     Frequency     –     Set     as     desired.   Refer to frequency selection. 3.     Mode – Set (USB, or AM). 4.     STO button – Push once. 5.     Set transmit frequency. 6.     STO button – Push again. NOTE If  another  channel  is  to  be  reset,  use  the smaller    concentric    knob    to    select    the channel and repeat the steps.  7.     To  return  to  an  operating  mode, push the PGM button. NOTE The mode for each channel (USB or AM) is stored   along   with   the   frequency.      If   the mode  is  changed,  the  system  will  receive and   transmit   in   the    mode    selected    for transmit. 3-4.  VHF COMMUNICATIONS TRANSCEIVERS (VHF-22D). a.   Introduction. The VHF communications transceivers  are  an  8.33  kHz  channel  spacing  cable system.    The  operation  between  the  25.00  kHz  and 8.33 kHz   modes   is   seamless.      Within   the   space occupied   by   each   25.00   kHz   frequency   exist   three 8.33 kHz   channels.      The   8.33   kHz   "frequency"   is referred  to  as  a  "channel,"  not  the  actual  frequency tuned.  The channel scheme avoids possible confusion associated   with   shared   25.00   kHz   and   8.33   kHz frequencies.  This method ensures that the equipment will  always  be  operating  in  the  proper  spacing  mode and    occurs    automatically    as    the    user    tunes    the