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Text File  |  1997-02-01  |  2KB  |  35 lines
  1.  
  2.         Here's a modification to the Yaesu FT-747GX to give you CW spotting
  3. capability. I'm using it on mine. Schematic and instructions follow:
  4.            J03
  5.         +----------+                              ^ to +5 volts
  6.         |to DN sw. |  1N4148          100K        |
  7.         |    O---------|<|-------+---^^^^^--------+
  8.         |to UP sw. |  1N4148     |               /       2N3906
  9.         |    O---------|<|-------+    100K     |/  E
  10.         |          |             +---^^^^^-----|         this circuit
  11.         +----------+                           |\  C     on display
  12.                                                  \       board
  13.   ................................................|....................
  14.                                                   | (shielded cable)
  15.                                                   |
  16.     this circuit                      1N4148      |  B _______
  17.     on main         from Q36   ---------|>|-------+---|       |
  18.     board           pin 7             (diode          | Q29   |
  19.                                        replaces       +-------+
  20.                                        jumper)
  21.  
  22.  
  23. (1) Replace jumper at base of Q29 on main board with 1N4148 diode.
  24. (2) Wire up 2N3906 circuit to display board.
  25. (3) UP/DN switches on mike will still function, and in CW mode you
  26.     will hear sidetone and can quickly spot proper frequency.
  27. (4) The sidetone oscillator on my FT-747GX measured 724 Hz, very close
  28.     to the 700 Hz CW offset in the FT-747GX, so by matching
  29.     the tones I can quickly "zero beat" the desired signal.
  30.  
  31. WA4VLV @ N4NIA.GA.USA.NA
  32. tijc02!jceng1!jkl141@uunet.uu.net
  33.  
  34. end of file
  35.