Heathkit FM-4 (1955–1956)
The Heathkit FM-4 is a standalone FM tuner kit from the mid-1950s. It sold for $49.95 in its first year. Documentation is thin. No frequency response, sensitivity, or distortion figures survive, and one source alone pins the production window down as 1955/1956. What is known comes largely from its Radiomuseum listing and scattered owner recollections. A period advertisement in High-Fidelity (April 1960, p.22) touted the AA-50 as "THE ALL-NEW, ALL-EXCELLENT STEREO AMPLIFIER-PREAMPLIFIER IN ONE LOW-COST PACKAGE!"
It's a simple, no-frills tube design. The circuit is a superheterodyne with two 12AU6 tubes, two-gang tuning and six circuits total. It runs on 117V AC, covers FM only, and measures 12.9 × 6.25 × 7.75 inches. It weighs 10.5 pounds. The listed "3 W power out" likely refers to an incidental output stage rather than an amplifier section, since this is a tuner and not a receiver. Forum threads from owners describe it as a budget kit relative to other Heathkit models of the era, and one writeup calls it a "simple, no-frills FM tuner," which matches the sparse spec sheet.
One oddity in the record: the Radiomuseum page title lists the model as "Heathkit AJ-14," but the body text consistently uses FM-4. This is treated as a title error, not evidence of a separate model. The FM-4 should not be confused with the similar-looking, valve-based model referenced in the Radiomuseum listing.
- Type: FM tuner kit
- Tubes: 2 × 12AU6
- Circuit: Superheterodyne, 2-gang tuning, 6 circuits
- Band: FM only
- Power: 117V AC
- Dimensions: 12.9 × 6.25 × 7.75 in (328 × 159 × 197 mm)
- Weight: 10.5 lb (4.76 kg)
- Original price: $49.95 (1955/1956)
No alignment instructions, antenna input specs, or common failure modes are documented. The 12AU6 tube type is noted, but current parts availability is unrecorded. If you own one and have measured its performance or know its output connector type, the archive would like to hear about it.
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