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ITT Marine STR 12

ITT Marine STR 12

The STR12, an older marine VHF from ITT Marine, can be modified quite easily with a discriminator output for the reception of AIS.

ITT Marine STR-12

The receiver IC, an SL660C, can be found on the left side of the circuit board. To reach the IC, the outside and inside covers have to be removed. The unfiltered audio can be found on pin 8 of the SL660.

Location of CR162
SL660 - pin 8 carries the unfiltered audio
The components used

Follow the next steps to make the discriminator output:

  • Connect a 10 k resistor, a 2.2 nF ceramic capacitor and a 10 uF electrolytic capacitor as shown on the picture. The plus pole of the 10 uF capacitor is connected to the resistor and the 2.2 nF capacitor.
  • Connect the core of a piece of shielded wire to the minus pole of the electrolytic capacitor
  • Connect the shield of this wire to ground, together with the free lead of the 2.2 nF capacitor. The two 47 pF capacitors next to the SL660 are a suitable ground point.
  • Connect the other side of the shielded wire with a 3.5 mm mono chassis socket
The connections to the IC and ground
The 3.5 mm chassis socket

The chassis socket can be mounted in the cover plate of the unused right input. Use some hot glue to fix the cover plate.

Photos and text: Henk van Rooijen

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