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Variable selectivity?
In article ,
Richard Knoppow wrote: James Millen was one of the founders of National but eventually was pushed out of the company. He started his own company, also in Malden Mass, and probably made many parts for National as well as his own stuff. Millen made very high quality components. Millen Mfg., at least at the time I worked there, was in direct competition with National Co. on several products, and neither company supplied the other. The National HRO was a revolutionary receiver in its day and stayed one of the favorites for both ham and commercial use for some thirty years. The mechanical design is attributed mostly to James Millen and the electronic design mostly to Herbert Hoover Jr., son of the president of the US. While the HRO was a legendary product, I'd hardly call it "revolutionary." It was a follow-on to the AGS line, with objectives to maintain AGS performance at lower cost-to-manufacture, and to normalize the coil-set interface so that the tuning coils could be built all-in-one-box and interchangeable. An examination of the schematic will show it to be essentially a copy of higher-end home entertainment circuits of the era, with a crystal filter and bfo added. Much of the actual performance came from use of better coils (house-built) in the RF and IF stages, a house-built tuning capacitor, and the house-built tuning dial was superior to almost anything else around. In short, a relatively straightforward tried-and-proven electrical design, but extremely well-executed in component quality and mechanical structure, pretty much hallmarks of Jim Millen's team. Worth noting that the NC-100, National's follow-on product, had similar performance, with the advantage of having internally-mounted and switchable tuning coils. Hank |
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