[Mondial]

In fact the capacitive dropper and the silicon diode trick won't work on alternative power line frequencies, if you set it up for a 60 cps power system it will not work on 50 cps, or anything other then 60 cps.

The diode and resistor dropper is independent of frequency. It will work exactly the same at 50 Hz or 60 Hz.

The RMS value of the AC voltage does not change with frequency. If you half wave rectify the AC, its heating effect will not change with frequency until you reach such a low freq that the filament temperature follows the individual cycles. This would only occur at a few cycles per second or lower, until you get to zero frequency (DC) where the diode would conduct constantly putting full voltage on the filaments, or not at all depending on polarity.