Don't forget to check your programming. If you're using the default programming downloaded from the database, it's likely that the radio is trying to scan distant tower sites which you can't quite receive very well and they'll be noisy; if you're having trouble picking up the first row of towers outside Miami County, an amplifier may help with reception of those towers, but then you'll be picking up the next row of towers beyond that, and they'll be noisy.
Having relatives in the area, I'm very familiar with Miami County. When I visit, I sometimes have issues receiving Montgomery County from Troy, even on higher ground. Since you're in Piqua, it's very possible that what's noisy are the towers in neighboring counties to the south.
First thing to check is to lock out ("avoid") all of the tower sites except the Miami County simulcast site, which your SDS200 should have no trouble with receiving. If that works, unlock (or "un-avoid") the next row of towers in surrounding counties one tower at a time.
By process of elimination, you'll figure out which towers you can receive clearly and which ones you can't, and can adjust your programming to suit the situation.
Also, don't forget that sometimes a transmission might be garbled because the person on the other end isn't getting into the system very well, which makes the transmission sound garbled to everyone.