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Demek / Shipmate RS 8000

RS 8000

It's not too difficult to make the marine VHF Demek / Shipmate RS 8100 suited for the recepton of AIS by adding a discriminator output.

RS 8000

The receiver IC, a TBA120S, can be found at the bottom side of the top circuit board. To reach the bottom side, two screws need to be removed, after which the top board can be expanded.

The baseband audio can be found on pin 8 of the receiver IC.

Location of the TBA120S
Discriminator Output
Pin 8 of the TBA120S contains the unfiltered audio
The discriminator output

Follow the next steps to make the discriminator output:

  • Connect a 1 k resistor to pin 8 of the TBA120S
  • Connect the positive lead of a 10 uF, 25V electrolytic capacitor to the other lead of the resistor
  • Connect the inner conductor of a piece of shielded wire to the negative lead of the capacitor
  • Connect the braid to the metal shield of the nearby coil
  • Connect the other side of the shielded wire to a 3.5 mm chassis socket
Removing the front

The 3.5 mm chassis socket can be mounted in the front panel without drilling, at the spot of the (obsolete) SELCAL test/reset button. To reach this spot, the front needs to be removed. When the caps of the dials are removed, the dials can be taken off the front by loosening their screws. By removing the four screws on the side, the front panel can be taken apart from the chassis.

Because the front panel is rather thick, the chassis terminal can be fixed to the panel with some glue from a glue gun. To align the chassis terminal's tip with the front, if needed , some plastic can be milled from the inside.

Exploded view of the front panel

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