Quote:
Originally Posted by rambo1152
So there would have been no simple TRF designs in America, as there were in the UK.
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The 1932 RCA 120 line test set was TRF.
All other fully electronic (i.e. no mechanical transmitter) sets were superhet.
Typical early IFs were in the 8-12 MHz range and were very complicated.
My TRK12 is 8MHZ audio, 12 video, uses discrete component bandpass filters
rather than transformers, and has a rock solid super great response curve,
fully capable of 1954 color TV. Its split AM sound. The TT5 is similar
but fewer IF stages. Note that prewar US TV was 441 lines; all sets work fine
at 525 an FM sound by slope detection.
What most WON'T work is nonstandard frequencies ... the fine tuning is
usually barely enough to tune in the audio. There were originally 5 channels which changed
TWICE to get to our current 5 "Band I" ones by 1947. The channel width and relative carrier positions
never changed from 1939 just the overall frequency.
Many prewar superhet tuners were horrendously bad designs which had vastly too-big
diameter round switches. This required things like 3/8 inch wide strap "inductors"
to get low enough inductance. This all at only about 96 MHz. But they are STABLE.