Sometimes the MW attenuation is nothing more than a pot or a resistor strapped and grounded. The email reflectors for the various radios are a great resource for finding out about these, and how to remove the attenuation
LW is another matter, sadly. I got booted off a Facebook group for saying this (heh) - there is no US broadcasting in the 155-281 khz range, so engineers see no reason to put together a good front end for that range. In fact, I don't think the ITU has allocated that band for broadcasting in the Americas. So if you hear US broadcasters on LW, it's likely to be a mixing product from strong MW stations. Some front end filtering will be necessary in such cases if you want to browse in that band. Hams have a couple of secondary allocations there, so in certain areas, you will hear digital modes that can be copied with the right software, and of course, NAVTEX can be heard primarily on 518 Khz, altho there are other frequencies less used as well. Here, loops are a primary antenna type - unless you have very understanding neighbors....Mike