Re: Marconi C100 B28 vs. Eddystones
The CR100 was introduced in about 1940, as the existing equipment could not be mass-produced. (There are surviving examples in the HMS Collingwood heritage collection, I don't think they would have had a high performance either.)
I restored a B28 from a very poor example a few years ago. I found that the paxolin insulation on the tag boards was leaky. I also had to replace the system switch wafer as it added to the problem. The main leakage path is from the HT rail to the AGC line. Mine had +12V on the AGC with no signal rather than 0V.
The Marconi CR100 manual is very helpful and repays close study.
I have attached a page from "Low Medium and High Frequency Communication to and from HM Ships" by Anderson and Grainger (1947). This paper explains much of the thinking at the time.
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