When an LC filter is designed to have less than 5% of BW from the central frequency, always get some critical influence of component values on the filter characteristic.
T type BPF has a better distribution of the loaded-Q on the filter elements, making this influence less stringent.
Try this schematic and see what you get. Inductor values are not standard, but this can be obtained using standard values inductors placed in series. Anyway, all the components should have low tolerances.
I don't know what you did wrong with your simulator, but results should be as in the picture attached.
I am using for many years this topology, without variable capacitors. T-type BPF require high-Q inductors, which anyway you need with any type of filter if you want to get less that 5% of filter bandwidth.
Like This.
View attachment 131202
Er... yes, but that is not what vfone was suggesting.What I meant is, isn't it physically impossible to have a wire of length 10 mm to be wound over 5 mm diameter with 9 turns.
Er... yes, but that is not what vfone was suggesting.
Usually the diameter refers to inside diameter.
So you get a 5mm drill, wind your coil, and maybe stretch it to 10mm (if required}.
That is the standard way of specifying a coil.
View attachment 131208
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