1Ж42А. As a mixer/Frequency changer????

[Amie]

....I've seen diodes used as in Trevor's diagram occasionally....

No, I've never seen a single diode in an official circuit like that....

Just to answer the contradiction....

Well, I have, the Radio Shack/Tandy Globe Patrol transistor radio is an example. I have one.

Reading on the internet the consensus is that the circuit is known as a floating detector that relies on the inherent leakage of the diode to work, it isn't good practice obviously, but does ensure that the only load to the signal seen by the preceding circuit is whatever the detector is driving, probably the reason for Trevor's excellent results.

The Radio shack version was sold as a kit and a promisingly comprehensive manual was provided, but unfortunately the circuit description of the detector doesn't explain exactly how it works.

Also in this particular example because it's a regenerative stage preceding the detector and inherently non linear, the diode may be completely redundant anyway.

A web page that has the circuit and a link to a PDF of the manual can be found at:
https://people.ohio.edu/postr/bapix/RSglobeP.htm

Trevor:
As a suggested method if you wanted to construct a sensitive infinite impedance detector for the radio using those valves, could you use a floating supply for the filament? A separate LT cell for each valve wouldn't be a hardship....but then why fix what isn't broken?

Very interesting. Thanks for sharing!

Amie.