Modifications for the Kenwood TS-811

9K6 baud modifications for KENWOOD TS-711 & TS-811


The following modifications, while not guaranteed certainly work on my radios:

I do not use the ACC 1 Connector on the back panel so I have removed the plastic plug and mounted a five pin DIN socket, although you can use any socket that fits.

The requirement for the 9600 baud modem is that transmit audio must modulate the varactor directly, and receive audio must come directly from the discriminator output, both these points are fairly easily accessable;

USE GOOD QUALITY AUDIO SCREENED CABLE FOR CONNECTIONS
  1. Remove top and bottom covers of TS 711/811.
  2. Turn set upside down and locate the PCB marked IF Unit X 48-1400-01 it is the large one on the left facing the rear of the set.
Mark, zl1tre

RECEIVE AUDIO

  1. Locate R 173 (3.3K), at the rear left side of the IF Unit PCB alongside a 1 ufd electrolytic capacitor (C 163). The connection to the discriminator output should be made at the junction of R 173, C 159, R 199 and C 163. I did this with a very fine tip soldering iron by soldering to the lead of R 173 nearest to C 163 although it could be soldered under the board if your iron is not small enough. The earth screen I soldered to a lug under the screw head located close by at the corner of the board.
  2. Run the cable to the socket on the rear panel and wire as desired.
TRANSMIT AUDIO

  1. On the same PCB at the front right (facing rear) locate R 11, mounted upright alongside J2 (4 way socket). Connection to the Varactor can be made at Pin 2 of J2 or as I did by carefully filing the lead of R 11 and soldering to it directly. The earth shield I soldered to a lug under the PCB corner mounting screw.
    This earth is also available at J2 Pin 1.
  2. Run the cable to the socket on the rear panel and wire as desired.
  3. If you have a scope available, set the tx level to 1.5v P to P at position FMM. If no scope, set the tx level pot on the G3RUH modem to the 11 oclock position and experiment.
UoSAT 3 only requires TX Audio from the 711 and RX Audio from the 811 but I would recommend wiring both in each set for future satellites such as RUDAK etc. You will also need to provide a Push to talk connection to your TNC either from the ACC 2 connector or mic socket. I wired from the back of the ACC 2 connector to the DIN socket that I mounted in the spare hole.
Good luck, ZL1TRE, Auckland, New Zealand.


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