Band pass filter bandwidth problem
The problem with passive filters is they are lossy, and can have attenuation lower than 0dB even in the passband. 

There are a few ways to over come this with active elements:


Boost the signal (say 10dB) before the filter with an amplifier
Implement a sallen key active bandpass filter:

Source: https://en.wikipedia.org/wiki/Sallen%E2%80%93Key_topology
Or if you require passives use an LC filter:

Source: https://rf-tools.com/lc-filter/