In article ,
Ralph Mowery wrote:

As hams are not reqired to keep the spacing or deviation some areas did
go to 20 kHz spacing and 5 kHz deviation. Other areas went to 15 kHz
spacing and kept the 5 kHz deviation. If the rigs are not very well up
todate and the frequency and deviation set correctly there can be
problems with the 15 kHz spacing.

Yup. Here in NoCal, some parts of the 2-meter spectrum use 20 kHz
spacing, and others use 15 kHz. There was a proposal to move things
down to even narrower 12.5 kHz spacings a few years ago, but some
experiments (which I helped perform) demonstrated that a lot of the
then-available mobile and hand-held radios would suffer some pretty
severe adjacent-channel bleed-through - their IF filters aren't
sharp/narrow enough to avoid it. Getting people to cut their peak
deviation down to 2.5 kHz would also have been difficult (older radios
often don't have this available as an option, and those that do are
often easy to mis-adjust).

The 440 band is still on 20 kHz spacings. Keeping peoples' transmit
oscillators accurately centered within 1 kHz or so is harder, up at
those higher frequencies, and it pays to make allowance for some
amount of drift when doing the frequency planning.