The original TMCC base puts out a 7 volt PP signal but excessive track loading and poor coupling and the inability to filter all frequencies except 455 kHz make it problematic in demanding layouts. My device also puts out 7 volts PP but does it cleanly. If Lionel can put 7 v PP into a large metal structure and not have FCC problems then my device is nothing different. I have never detected any trouble with AM radios in the train room with TMCC with or without my device.
Legal or not, I dont see a problem with this setup.
Very few people use AM receivers anymore and those that do wouldn't notice.
I know of nothing else operating in that freq and unless someone else was actively sniffing around any activity would go unnoticed.
Ham operators (and the FCC) know that there a pirates operating across the entire spectrum but rarely are any ever caught.
