Re: Infinite Impedance detectors.
Also intrigued that this arrangement is discussed in publications dated 1953 and 1956- surely, they would have been tried/researched before then, even in the mid-'30s as AM radio and valve refinement really got into stride? Mid '50s seems to be when FM radio was catching on and the AM side of radios was really getting sidelined by price-conscious manufacturers- certainly as regards any refinement that involved complication. Certainly, if the EABC80 and equivalents could offer a one-envelope good-enough solution to AM/FM demodulation and AF amp, it's difficult to imagine mainstream manufacturers doing this. Even if EB91/ECC83 would offer all-separate cathodes for optimum-performance of delay AVC, low-distortion biased detector, cathode follower and AF amp.
I think that, culturally as much as anything else, AM radio continued to be seen as a parallel option, rather than obsoleted companion, to FM in the US- perhaps there were high-quality tuners/receivers there that continued to try to get the best from the medium with configurations like the above.
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