There was a discussion on the russian boombox enthusiasts forum shizaudio regarding expanding the FM band coverage of the National RX-7200. A member of that board (Vlad33) posted and shared his mod, unfortunately it was in Russian. Fortunately Boomboxery member Alex (Mystic Traveler) is also a member there, and has donated his time (in collaboration with Vladimir) to collect, summarize and translate that process so that that knowledge is available to English speaking crowd too.
I have included the how-to into our WikiBoombox archive. For those that are interested, you may view the article, as well as the RX-7200 wiki there.