Amature Radio Pre-Selector Idea

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1

I am thinking of making an amature radio pre-selector/filter for HF (3-30MHz) that has selectable bandwidth and gain control after seeing some info on parametric equalizers. I will attach the two boilerplate schematics on the layout.

My main question is besides the obvious frequency characteristics of the parts what are some pointers I should adhere to so that I keep system noise as low as possible. (Ideally <110db)

The schematics above are simple for the audio spectrum with very little variance, so im not sure without some testing on if you can get a 3-30MHZ tunable frequency out of that circuit. Just an idea I had this morning and wanted to see if I had missed any glaringly obvious to make this not work.

2

get a 3-30MHZ tunable frequency out of that circuit.

Extremely unlikely.

3

The whole reason I am trying to do this via actives is if you use an LC network to tune your antenna the -3db bandwidth is quite small and not as suitable for SDR receivers. With an old style receiver you can only hear one freq at a time so twiddling two nobs is quite simple.

Is there any way to expand the bandwidth of an LC resonant freq antenna?