In article , Alan Douglas
adouglasatgis.net writes:

Interestingly, Sparton got around
Alexanderson's patent by putting all the tuning at the front end,
feeding a series of untuned RF stages.

I restored one of those Sparton radios, and it works very well -- every bit as
selective as any other 4-stage TRF AM-BC set of the time.

I also have a spare tuned front end from that project, which I keep intending
to use as a "secret weapon" preselector ahead of a modern AM rx for BC DXing.
--Mike K.
..
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