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Text File  |  1992-09-15  |  1KB  |  26 lines
  1. SCA.4
  2.                     weak pilot   suppressed    just a
  3.                      carrier      carrier     boundary              FM
  4.                        /            /             /             sideband
  5.                       /            /             /          sub    /
  6.                      /            /             /           car.  /
  7. |             |             |             |            |   /
  8. | Normal FM   | (A-B) Lower | (A-B) Upper |        /||||||||\
  9. | audio (A+B) |  Sideband   |  Sideband   |     /||||S|C|A|||||\
  10. |             |             |             |  /|||||S|i|g|n|a|l|||||\
  11. DC           19KHz        38KHz         53KHz        67KHz
  12. --monaural
  13.     signal----
  14. --------stereo composite signal-----------
  15. -------------full composite (stereo + SCA) signal-------------------
  16.  
  17.  
  18.  
  19. Now to the main point.  The FM transmitter takes this composite audio
  20. signal as input and FM MODULATES its carrier with it.  When this is
  21. received by an FM receiver, what comes out of the discriminator is the
  22. composite signal.  In a normal monaural FM receiver, this is fed to the
  23. volume control and thence to the audio amplifier stages, where
  24. "de-emphasis" is applied as noted above, and finally out to the speakers
  25. or headphones.
  26. CONTINUED IN SCA.5