Indoor antenna like the MFJ or Tun-4 has a lot of gain and while they have a gain control, too few folks know how to use it properly. You don't ever run it flat out at 100%, because as noted, it just begins to amplify the noise instead of the signal. The lower bands tend to be noisier and thus would need less gain. Every RF environ is different, and you really need to listen to the band to determine at just what point the receiver's AGC kicks in, and you start getting more noise than signal. It can and does change depending on the frequency
I looked at that Fat-Man - looks like a vertical metal tape measure used as an antenna - which in an apartment, might not be the best choice. Many verticals are noise magnets, so I'd hesitate. Interesting building it, though, altho it does show it needs several radials
Mike