The difference between OOK (On/Off Keying), FSK (Frequency Shifting Keying) and GFSK (Gaussian filtered Frequency Shifting Keying) is evident.
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The worst kind is OOK because data rate 'modulate' main frequency and it produces wide spectra. Much better is fsk, which is very similar to TTY or teleprinter if baud rate is very low. Even better is GFSK, which is FSK with slow transition between two tones or two frequencies. There is also ASK (Amplitude Shifting Keying), but Si4432 has no such ability to produce this modulation. ASK has much narrower 'footprint' than OOK because it does not goes from zero output to maximum, but rather from some 5% of the power up to 100%. No abrupt switching. Car keys has OOK (well, mostly) because it is easier to apply on small transmitter - just turn on and off TX, and that is all. Since it is short burst, nobody cares. But for communication between two transceivers, we should use GFSK - much less wasting power to unwanted side-bands.
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