When selecting an SSB transmitting frequency, what minimum separation should be used to minimize interference to stations on adjacent frequencies?
Why A typical amateur SSB signal occupies roughly 2 to 3 kHz of spectrum, so your carrier (dial) frequency must be at least that far from the next station's dial frequency for the two sidebands not to overlap. Spacing closer than the signal's own bandwidth guarantees splatter into the adjacent QSO even if both transmitters are clean. So the minimum practical separation equals the SSB bandwidth itself, about 2 to 3 kHz.
Watch out The choice of about 6 kHz is roughly the bandwidth of an AM signal (two sidebands plus carrier) and is more separation than SSB needs; the choices in hertz are far narrower than any voice signal and would put you right on top of the other station.
SSB is about 3 kHz wide, so stay about 3 kHz away. Bandwidth equals minimum spacing.