I have a Zenith C845 radio with a 6BJ6 tube, which is identified on the schematic simply as an RF amplifier. The AM Wavemagnet looks as if it is connected (through a section of the band switch) to the grid of this tube when the band switch is set on AM. Is this amplifier tube used on both AM and FM or just FM?
As sensitive and selective as the C845 is on AM (I can hear a 5kW oldies station 35 miles from here, and next to another 5kW station 40 miles distant to boot, fairly well during the day on this set), it wouldn't surprise me if that tube is doing double duty as an AM and FM RF amp.