FT757GX

NARROW CW FILTER MOD FOR RTTY/AMTOR...YAESU FT-757GXII

MOD BY N7CR ES N7DYX

THE PURPOSE OF THIS MODIFICATION IS TO PERMIT NORMAL SSB FILTER ON
TRANSMIT WITH THE NARROW CW FILTER ON RECEIVE. THE PASSBAND FALLS
INTO PLACE IN THE LSB MODE.

NO NEED TO RETUNE ANY OSCILLATORS, SINCE THE PASSBAND CREATED BY THE
MODIFICATION PUTS THE CENTER FREQUENCY AT THE PROPER FREQS. FOR
2125/2295 (170 HZ SHIFT) MODEM TONES.

THE WIRE "COLORS" ARE FOR REFERENCE ONLY. USE WHATEVER YOU WISH.
THE WIRE WE USEDIS SOLID CONDUCTOR "MA BELL" WIRE, BUT WIRE WRAP
WIRE WORKS JUST FINE.

THIS MOD DIFFERS FROM THE MOD FOR THE FT-757GX IN MECHANICS AS WELL
AS ELECTRONICS, AS THE BOARDS IN EACH OF THE RIGS ARE ENTIRELY
DIFFERENT.

YOU WILL NEED: (2) 1N4148 DIODES, (5) PCS WIRE, (1) DOUBLE POLE/DOUBLE
THROW SWITCH. (WE USED A SLIDE SWITCH AND MOUNTED IT NEXT TO THE SWR
SWITCH ON THE REAR PANEL.)

THE SWITCH DIAGRAM HERE IS LOOKING AT THE SWITCH FROM THE CONTACT SIDE.

WIRE COLORS:  W=WHITE, BRN=BROWN, R=RED, BL=BLUE, YE=YELLOW

THE MOD IS DONE ON THE "RF BOARD"

SWITCH DIAGRAM:      "W" ON *   * ON "R"

                  "BRN"  B  *   * A "BL"

                        NC *   * OFF "YESO

1. REMOVE RF BOARD

2. REMOVE CATHODE OF D102 FROM BOARD (THIS DIODE WILL NOT BE USED).
   INSTALL NEW 1N4148 CATHODE TO BOARD,IN PLACE OF D102 CATHODE.
   SOLDER ANODE TO "BLUE" WIRE.

   FREE END OF WIRE TO CENTER A PIN OF SWITCH.

3. DRILL HOLE NEXT TO PIN 5 OF J10. CONNECT "YELLOW" WIRE TO PIN 5
   SOLDER TRACE. FREE END OF WIRE TO 'A'"OFF" PIN OF SWITCH.

4. DRILL HOLE IN COLLECTOR TRACE OF Q56. CONNECT "RED" WIRE HERE,(TX 8V)
   FREE END OF WIRE TO 'A' "ON" PIN OF SWITCH.

5. DRILL HOLE AND INSTALL THE OTHER 1N4148 CATHODE AT THE JUNCTION OF
   C106/R61. ANODE TO "WHITE" WIRE. FREE END OF WIRE TO 'B' "ON" PIN
   OF SWITCH.

6. DRILL HOLE AND CONNECT "BROWN" WIRE TO JUNCTION OF R40/R57, (RCV 8V).
   FREE END OF WIRE TO CENTER 'B' PIN OF SWITCH.

7. OFF CONTACT OF 'B' POLE NOT USED.

   THIS CONCLUDES THE MOD FOR USING THE NARROW CW FILTER ON RTTY/AMTOR.
WE HAVE FOUND THAT THIS MOD WILL MAKE TUNING MUCH SHARPER AND WILL
GREATLY IMPROVE RECEPTION OF THESE MODES.

   THANKS TO THE YAESU ENGINEERS FOR THEIR FORESIGHT

            ENJOY ES 73

            N7CR @ N7CR.#SPOKN.WA.USA.NA
           N7DYX @ N7CR.#SPOKN.WA.USA.NA