AM Mod Monitor Antenna

[Bill DeFelice]

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.

Thoughts?

[Deep Thought]

That's the ferrite rod antenna. You should be able to find them fairly easily. The value is not terribly critical in this circuit.

[Bill DeFelice]

I was curious since, being a ferrite antenna, there was no provision for tuning across the band. I would guess the physical size would have to be fairly large to allow for good performance across the band which is why I thought I'd pose the question prior to attempting my build.