I was intrigued by the long discontinued Inovonics AM active antenna. I wanted to attempt to build something like this as I often use a 520 modulation monitor for field testing and it would be nice to have a broadband AM antenna that doesn't require peaking. I have an old loop but I haven't rewound it to improve its performance on the x-band.
I took a look at the schematic for this antenna, which is included in the Active Antenna Interface PDF document on their site. Their antenna is a rod-type affair and in the schematic is referred to as the "coil of mystery" with no value or other detail mentioned.
I'm just wondering how difficult it would be to replicate this and if there's a particular type of ferrite coil I should use in my attempt.