I wanted to build this Active Antenna circuit for my short wave radio receivers. The basic design is called the pa0rdt Mini Whip. Many versions can be purchased online.
What were you using for an antenna that you felt those back to back diodes on the J310 would be needed? That's not going to do much except add some IMD.
The diodes are static protection for the FET. Not sure what you mean by IMD being introduced. The RF level is so low it will never reach the .7v necessary to cause the diodes to conduct. One thing I was concerned about was junction capacitance of the diodes rolling off the higher frequencies. Capacitance of the 914 is quite low.
