478 MHz band, allowed for hobbyist use in USA?
According to the chart here, 478 MHz falls into a band that is allocated to Fixed Land Mobile Broadcasting.  The description says, "The federal agencies use this band for land mobile radio communication systems for shared systems and mutual aid responses with public safety agencies (fire fighting, law enforcement, medical, etc.) in local communities."  According to the footnotes (which can be found here), none of these applications includes unlicensed use.

478 MHz is not an allocated amateur band, so even if you had a ham license you could not transmit on that frequency.

The Wikipedia page on industrial, scientific and medical (ISM) usage also lists the frequency bands that are allocated for unlicensed use.  478 MHz is not on that list.

Based on this evidence it is illegal for you to use a transmitter on 478 MHz in the United States.