Argus25: – Thanks for the correction. Appearances can be deceptive!
Ukcol: - I am inclined to think that the Geisler article was somewhat overstated as to the benefits of the voltage-doubling AM demodulator. Perhaps there is some small gain as compared with the simple diode. Heathkit claimed lower distortion for it, but did not quantify or explain further.
As you say, TV AM sound does appear to be an easier case, with RF in the 30 MHz range. That is true even if one considers the extended “audio” bandwidth needed for proper operation of rate-ot-rise noise limiting diodes, say around 100 kHz. Mostly I think conventional diode demodulators were used for TV AM sound in the valve and discrete semiconductor eras. In the IC era, for French Systems E/L and then L/L’, quasi-synchronous demodulators, both with and without carrier tank circuits, generally took over. It would appear that the with-tank-circuit type simply followed established vision demodulator practice, and that the without-tank-circuit type was developed to cover multi-system receivers in which L and L’ had different sound IFs. Nevertheless, National developed an IC for TV AM sound that used a rectifying demodulator, whose exact nature I hesitate to categorize:
Cheers,