Eighties Retro Radio

Rewind time back to 1988 and an ‘el cheapo’ FM stereo tuner kit looked like this! The three modules pictured below consisted of an:

  • FM tuner (steel shielded front end),
  • Intermediate Frequency/detector (IF) &
  • FM stereo decoder.

The three modules connect together with 28 inexpensive supporting components to comprise a fully functioning FM/AM tuner with a basic signal strength meter, LED stereo indicator & coaxial cable antenna input.

Tuner module © 2014 FM DXing at WordPress

Module for IF & Detector © 2014 FM DXing at WordPress

Module for Stereo Decoder © 2014 FM DXing at WordPress

The tuner featured analogue tuning with switchable Automatic Frequency Control (AFC) feature. AFC is rarely mentioned these days. In a nutshell, AFC circuitry automatically locks to the tuned frequency so as to facilitate ‘drift free’ reception of the desired FM broadcast; automatic correction is applied when the dial is ‘off-tuned’. In a congested FM band, the function is best switched off, otherwise that weak signal might be hard to find.

Contents of Electronics Australia magazine © 1988 Federal PublishingCover of Electronics Australia magazine © 1988 Federal Publishing

The above tuner was featured as a Do It Yourself (DIY) kit in the now defunct Electronics Australia magazine (above) from April 1988. Hand written & printed schematic diagrams and modules (above) were found in buried in an old set of drawers.

The schematics for each module appear below:

FM tuner schematic © 2014 FM DXing at WordPress

FM IF & detector schematic © 2014 FM DXing at WordPress

Stereo decoder schematic © 2014 FM DXing at WordPress

Further reading

1974 MPX-stereo decoder with TCA290A

TCA420a datasheet

AFC Definition

AFC Explained

What is AFC?

Why choose plain FM over FM AFC?

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