Is saying "GFSK" self-defining? Are there variations on the techniques to reduce occupied bandwidth?
Would this spectrum signature be such that a simple FSK receiver cannot demodulate a GFSK signal?
And vice-versa, GFSK receiver demodulating an FSK transmission?
(Assuming one can adjust/fiddle with the receiver bandwidth, modulation index, etc. for the FSK system but the GFSK system cannot be altered)