In an rf-unfriendly environment like yours, the best thing you can do before putting up any antenna indoors / patio / window, etc, is to use the portability factor of the 750 and try to find the least-noisy locations first. Move it around, change the angle of the antenna from vertical to horizontal to diagonal - whatever it takes to find the least amount of noise without totally shielding it from the signals themselves.
Compare results by running solely from batteries as opposed to using the power adapter. In this situation, a smaller antenna in a quiet location is usually more beneficial than running wire all over the place that crosses into local noise fields.
When you have found that spot, you can plan to put an antenna in that location. Read the other threads here for those that are in much the same situation as yours, condo / basement / college dorm etc for more ideas on what types of small antennas you might want to look into. Without being there, it is hard to make an overall recommendation with a guarantee, but the portability of the 750 will certainly make that job of hunting down a quiet location easier - sometimes a few feet can make all the difference.