Polyphemus reacted to chicken in [POTM] dAISy - A Simple AIS Receiver
Yes, dAISy includes a bandpass filter.
I experimented with external LNAs a few times, but didn't see any benefit. Though I never was very systematic about my experiments.
The max input must not exceed 10 dBm. Even -50 dBm is more than enough to reliably decode a signal. A LNA would only be useful if it pulls very weak signals (say below -100 dBm) out of the noise.