Yes,
the minimum modulation in Fm it's +/- 5,6 khz .
Under this limits the modulation it' s NOT applied to carrier (no tone received in radio).
Over the tone appears ..
Try to generate a Fm signal at 10,7 mhz and receive with a fm 88-108 mhz radio place in contact tp the central of bnc output with a shorth piece of wire.
Then decrease the % of modulation and listen..