Modifications for the Yaesu FT-2700

Modifications for the Yaesu FT-2700
YAESU FT-2700 straping

                        YAESU FT-2700
   --------------------------------------------------------------------
   D09 D10 D11 D12
     0   0   0   0     NO WORK
     0   0   0   1     AS SHIPPED
     0   0   1   0     -151.600
     0   0   1   1     144-154 MHZ  12/25
     0   1   0   0     -151.600
     0   1   0   1     144-148 MHZ  12/25
     0   1   1   0     144-154 MHZ   5/10
     0   1   1   1     144-146 MHZ  10/20
     1   0   0   0     -151-
     1   0   0   1     144-146 MHZ  12/25
     1   0   1   0     144-146 MHZ   5/10
     1   0   1   1     144-146 MHZ  10/20
     1   1   0   0     -151.600
     1   1   0   1     140.150      12/25
     1   1   1   0     144-148 MHZ   5/10
     1   1   1   1     144-154 MHZ  10/20
    -------------------------------------------------------------------
    -                        UHF SETTING                              -
    -------------------------------------------------------------------
    D13 D14 D15
      0   0   0        NO WORK
      0   0   1        430-440 MHZ  12/25
      0   1   0        430-450 MHZ  12/25
      0   1   1        430-440 MHZ   5/10
      1   0   0        *NORMAL* AS SHIPPED
      1   0   1        430-440 MHZ  12/25
      1   1   0        430-440 MHZ  12/25
      1   1   1        430-450 MHZ   5/10

FT-2700RH cross band repeater modification

I have been asked a couple of times to send the mod I devised to use this rig in cross-band repeater mode. I've always been a bit reluctant cuz it is not a "cut this trace" or "remove this jumper" type of mod. It is not for the faint at heart HI. It works quite well indeed, though. So here it goes.

Making the modification:

Use care, and take your time. This is not an easy one!
Encapsulate both modules in isolating material - I used electric tape.
Make good connections.
Before you apply power to test the mod, ensure the "dim" button is released. Turn the radio on. Test it to see it works just as before.
Nothing should have changed except for the "dim" button.

Using the mod:
Say you want to cross-link 146.52 simplex to a UHF repeater on 442.00+.

Program memory channel #1: 146.52 rx, 447.00 tx, full duplex (consult your manual if necessary on how to do that).
Program memory channel #2: 442.00 rx, 146.52 tx, full duplex.
Lock out all other memory channels so they will not scan.
Select either memory #1 or #2 - doesn't matter.
Push "dim" button in. This button has become the RPT ON/OFF switch.

Testing:

You should see the 2700 scanning between channels #1 and #2 at a rate of about 3 cps. Open the squelch and you should see the tx coming on the air. Close the squelch and scanning should resume. Note that the rx volume control has no effect on audio level going out on the air.

Now the pot VR1 will need to be adjusted. There are 3 ways of doing that:

Use reports from other stations
Better than that, use the old VU METER trick.
Best, use a deviation monitor.

MODULE "A" |

NOTE #3    |                       [X]

-----------+              Q1        |          VHF UNIT

VHF UNIT                  +--C---------------->J04   (SEE NOTE #1)

J04   <------R1---------B-|                    PIN #3

PIN #6               |    +<-E-+

                     R2        |

                     |         |

                  +--|--------------------+

                 K1  |                   K2

CNTL UNIT         +-----------------------+

JP01  <--------o----           |          -----o---------VR1------ NC

PIN #3             +---+       |      +---+               |

                       |       |      |                   C1

                     +---+     |      |                   |            PLL UNIT

                      GND      |      |                   +----------->J03

VHF UNIT                       |      |           VHF UNIT             PIN #2

J02    <-----------------------|      +---------->J02

PIN #7                         |                  PIN #4

- - - - - - - - - - - - - - - -|- - - - - - - - - - - - - - - - - - - - - - - -

MODULE "B" |               +---|

NOTE #3    |               |   |

-----------+               |   R3

                           |   +------R4------+

                           |   |   +----------|

                           |   |   |          |

                        +--+---+---+------+   |

                    U1  |  8   7   6   5  |   |

           SEE NOTE #2  |  1   2   3   4  |   |

                        +--+---+---+------+   |

                           |   +---|----------+

            [X] <----------+   |   |                       CNTL UNIT

                               C2  +-------------|<+------>JP01
                               |                 D1        PIN #5

                             +---+

                              GND

Note #1:

Cut orange wire coming out from plug.

Solder two wires to orange wire coming from CNTL unit, one each to points marked [X] on the diagram above.

Solder orange wire from plug, pin 3, to ground for dim display light, or leave unconnected for bright display light.

Note #2:

Pins #4 and #5 of U1 are No Connection

Note #3:

Both modules are built separately, and encapsulated to prevent shorts
Module "A" is located on top of PA module on VHF board
Module "B" is tucked behind CNTL panel in front of radio.
Components:

   R1: 2.2K             C1: 0.1 UFD             K1 & K2: reed relays,

   R2: 3.2K             C2: 10 UFD                       12V @ 1050 ohms

   R3: 47K              VR1: 35K pot                     RS #275-233

   R4: 15K              D1: 1N914 diode         U1: NE555

   Q1: 2N3638A or equivalent

9k6 & FT-2700RH

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