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Sony Air-7

Sony Air-7

The Sony Air-7 is a vintage receiver. Thanks to the spacious layout, it's not to difficult to equip it with a discriminator output.

This receiver uses a discriminator circuit with discrete components: a ceramic filter and two diodes. The unfiltered audio can be found on the cathode of diode D23.

The linearity of this discriminator circuit is poor and therefore less suited for AIS. However, the Air-7 performs well as a paging receiver.

schematic diagram
The cathode of D23 contains the unfiltered audio
The right pin of D23 is the cathode
Use the next steps to make a discriminator output:
  • Solder a 10 k resistor to the cathode of D23
  • Connect a 2.2 nF capacitor with the resistor's other lead
  • Solder the other lead of this capacitor to ground, e.g. the metal shield of the coil nearby.
  • Connect a 10 uF, 25 V electrolytic capacitor with its negative lead to the junction of the resistor and the 2.2 nF capacitor
discriminator output
The components for the discriminator output
These two wires need to be connected
The earphone socket can be reused.
  • Follow the wires from the earphone socket to the bottom of the scanner
  • Cut the wires
  • Connect the red and yellow wires and isolate them with tape or shrink tubing. This reconnects the loudspeaker.
  • Connect the red wire coming from the earphone socket to the positive lead of the electrolytic capacitor
  • Solder the black wire running from the socket to ground
Overview of the discriminator output

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