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Variable selectivity?
"gareth" wrote in message ... Further information most welcome, thank-you In the 1948 Radio handbook which I mentioned previously, there are adverts from a company by the name of Millen, and I assumed it was the same guy after he had left National. Your comment about a phenolic intersperser is no doubt some means of isolating an earthy contact? It would be interesting to know from the Lamb patent whether he proposed therein the technique of Single Signal Reception by the use of the phasing control to null out the audio image, or whether this was something that came about through experience? I think this was part of Lamb's original intention. The articles originally describing the use of the filter were aimed at "single signal" reception, meaning that the audio image was suppressed. The Lamb filter required some juggling between the bandwidth and phasing adjustments to get the response to where the operator wanted it since they interacted with each other and with the center frequency. Nonetheless, the filter worked very well and provided an order of magnitude better selectivity than was available previously. 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. There is considerable history of both National and Millen, including a Millen Society, on the web, a Google search will find it. 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. -- -- Richard Knoppow Los Angeles WB6KBL |
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