As the FT101E has lots of tubes in it I doubt that you will do much damage HOWEVER:
1) Place a couple of back to back 1W 5 volt zener diodes across the input.
2) Find a couple of reed relays. Wire the first relay across the two diodes and power the coil with the transmit power so that it is closed when you transmit. Wire the second reed relay in series with the receiver coax and arrange for it to be closed on receive, switch using either your PTT line or some logic.
Email me if you can't figure this out and I'll send you a pdf diagram. Address is firstname.lastname@example.org