ln the mid 1930s James Millen and the National Company, Inc announced an innovation called the “Movable-Coil Tuning Unit”. The first of these “coil-catacomb” or “sliding-coil” receivers was introduced in 1936 and represented the first truly high-performance communication receivers that did not use plug-in coil sets. This receiver series continued to evolve and expand through WW2 and beyond with the addition of direct-reading dials and a single unified band-change and tuning control system.  By 1949 over 60 different receiver variants had been manufactured and many of these show up at swap meets and hamfests usually at very reasonable prices.

Antique Wireless Association Member and communications historian Brian Harrison, KN4R, tells the story of these revolutionary receivers in this presentation from the AWA Shares series.

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