This radios uses a 1 - 12BA6 as RF amplifier and 2 as IF amplifiers. FM requires more tubes than AM. Here is the circuit.

http://techpreservation.dyndns.org/schematics/51/51_General%20Electric_408_47.djvu

Norm

:Have not looked at the print of your AM/FM radio. But a 12BA6 is a remote cutoff pentode. This is used as a wide band RF amp for both AM & FM. Is also used for IF amp. Used again for converter. Many of the same tube number types can be used for different applications in radios.
:An AM/FM is a good example of this.