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Kelvin Hughes Husun 55

Husun 55

It's not too difficult to make the Kelvin Hughes Husun 55 marine VHF suited for the reception of AIS by adding a discriminator output.

Kelvin Hughes Husun 55

The receiver IC, a TK10420, can be reached easily. The unfiltered audio can be found on pin 9. It's quite strong (about 4 V peak-peak), which could damage a computer's soundcard. Therefore, an attenuation of about ten times is created by a two resistor voltage divider.

Location of the TK10420
Discriminator Output
Pin 9 of the TK10420 contains the baseband audio
The discriminator output

Follow the next steps to make the discriminator output:

  • Connect a 10 k resistor to pin 9 of the TK10420
  • Solder a 1 k resistor between the other lead of the 10 k resistor and ground. These two resistors create an attenuator
  • Connect the positive lead of a 10 uF, 26 V electrolytic capacitor to the junction of the two resistors
  • Connect a piece of isolated wire to the negative lead of the capacitor

    One of the 3.5 mm sockets in the back marked 'D/WATCH' can be reused:

  • Detach the brown and red wires from the socket and connect them. Isolate the solder connection, using shrink tube or isolation tape
  • Connect the wire coming from the capacitor to the low solder lug of the chassis socket
The D/WATCH socket
Reuse of one of the 3.5 mm sockets
Overview of the modification

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