I have to agree with @Sshannon. Definitely try an external antenna first. Even a mobile mag mount antenna on a cookie sheet outside is better than an antenna inside the house. If you can afford it and have a place to mount it, I will recommend the Comet CA-712EFC antenna.
And getting a 200 mile range is definitely not the norm with GMRS. Most guys in the wide open desert are getting 75 - 100 miles tops. Terrain, foliage, buildings and other obstacles will affect and limit your range.
GMRS is line of sight. So the higher your antenna is and that of the person you are trying to talk to is, the better.