In article ,
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
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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