I want to create a phantom power supply for an active car DAB-antenna (174 - 240 Mhz, 25mA), and I've been trying to read me up on how this is done. As you may know from my previous posts, I'm lacking a lot of the basics when it comes to electronics. So after some Google-fu, I found the following phantom power circuit for an active AM antenna at http://www.inovonicsbroadcast.com/wp-content/uploads/catablog/downloads/Active_Antenna_Interface.pdf

My understanding is that the 47uH inductor let DC pass, but stops AC. On https://e2e.ti.com/blogs_/b/analogwire/archive/2014/04/23/when-to-use-an-rf-choke-vs-an-inductor I found the formula

1. Is it actually this simple? No more filtering?

2. Should the inductor be of molded type (as in the AM example), or can it be any type?

3. Is there any problem selecting a higher inductance, lets say 1mH?

4. Is it OK to use 0.1uF ceramic for C1?

My understanding is that the 47uH inductor let DC pass, but stops AC. On https://e2e.ti.com/blogs_/b/analogwire/archive/2014/04/23/when-to-use-an-rf-choke-vs-an-inductor I found the formula

For the lowest AM frequency, 535 kHz, and 75 ohm impedance this gives a needed inductance of ~22uH. So it seems the 47uH gives some headroom. When using the formula for 174 Mhz and 50 ohm, the required inductance seems to be ~46nH. My proposed circuit then looks something like this:Z = 2π * freq * L

1. Is it actually this simple? No more filtering?

2. Should the inductor be of molded type (as in the AM example), or can it be any type?

3. Is there any problem selecting a higher inductance, lets say 1mH?

4. Is it OK to use 0.1uF ceramic for C1?

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