I am thinking of getting an MGL N16 VHF Nav radio with the MGL Vega V16 Control head. It has an interesting mode of operation (referred to as SCAN Mode) where the single receiver in the N16 rapidly switches back and forth between the primary and standby VHF frequencies. In this mode the Vega screen displays navigation information from both frequencies on the screen at the same time - (2 VORs, or a VOR and an ILS, for e.g.). Of course in this mode it is not on either frequency long enough to hear, or to decode the audible Morse code identifier, so the system does not send the audio to the intercom or display decoded ICAO call letters on the screen. With SCAN Mode off the Morse code from the one (primary) frequency is audible, and the screen shows the decoded 4-character identifier next to the frequency.
I was told (although I have not been able to locate a reference for this), that FARs require that you identify the Morse code identifier to legally use a VHF NAVAID signal for navigation.
So, although it is simple to turn the SCAN function on and off, do you need to have the Morse code identifier continuously, throughout the entire approach, to legally use a NAVAID for navigation? Or is it sufficient to do this once, on the initial portion of the approach, and then turn SCAN Mode on to concurrently monitor another NAVAID (like an airfield VOR while on an ILS approach)?