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Variable selectivity?
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gareth wrote: Path: eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: "gareth" Newsgroups: rec.radio.amateur.boatanchors,uk.radio.amateur Subject: Variable selectivity? Date: Sun, 13 Oct 2013 19:11:43 +0100 Organization: A noiseless patient Spider Lines: 62 Message-ID: References: Injection-Date: Sun, 13 Oct 2013 18:11:44 +0000 (UTC) Injection-Info: mx05.eternal-september.org; posting-host="7eed01e16f1b726e7bf0868184e40653"; logging-data="3180"; "; posting-account="U2FsdGVkX1+1JzqQMmyCzyCfOW7Zs0Hn/3jBXvXa3C4=" X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-RFC2646: Format=Flowed; Response X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 Cancel-Lock: sha1:srPnYezJ15BqABsrB2fkVqKopN0= X-Priority: 3 X-MSMail-Priority: Normal Xref: news.eternal-september.org rec.radio.amateur.boatanchors:3527 uk.radio.amateur:189325 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. I'm a bit surprised to see any doubt about James Millen as the honcho of National Company before 1939, his departure from National, and his setting up James Millen Manufacturing in Malden, Mass. a short distance from National in 1939-40. Yes, there was only one James Millen. There are a couple of web sites devoted to (Jim) Millen's history. I worked for James Millen Mfg. for a couple of years in the 1950's, so know a bit about Millen and some of the history behind the 1939 split with National. It was never entirely clear to me just what went on---on the one hand, a desire on the part of National's principal money backers to go public, and to move the company in different directions, with more consumer products; also, some financial things that reduced the money that Millen and his close associates (most or all of whom moved to Millen Mfg.) got from National. Your comment about a phenolic intersperser is no doubt some means of isolating an earthy contact? I don't know about Hammarlund's variable coupling IF's in any detail, but I'd suspect that the interposition of a phenolic piece was for mechanical reasons, not electrical. Millen offered a line of IF transformers (455 and 1600 Khz) that used adjustable capacitive coupling only between the coils---one of my projects when I worked there. 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? So far as I know, Lamb's single signal focus was on CW reception with no audio content. As I recall, phasing the crystal filter came later. Early (1933-34) production receivers I know of that used Lamb's principles were the National AGS-X and FB-7X; and the RME-9D. Hank |
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