That might only be because you're so close to their tower. On the contrary if you were using Jackson County's tower you'd have greater range than OSPD's vhf tower. Jackson County has 3 sites, one being several hundred feet above sea level on Wade-Vancleave Rd. in Vancleave, with that tower they can go well into George County on a portable and still communicate with other units. The other two towers are on the coast, One is located at the EOC outside of the Sheriff's office in Pascagoula, and the third is located on a tower directly behind the Fountainbleu VFD on Hwy 57 just south of Hwy 90 in Ocean Springs.
The radio picks up the strongest signal from each tower and uses it. So regardless where a user is in the county they have 3 choices to get a good signal. I haven't quite figured out how this would work with a scanner. I'm pretty sure the control channel is coming from the wade vancleave site. which I believe is still the prime site. So yeah it's a bit weak.
As for Biloxi, they have a tower over here in east harrison county, probably on top of their dispatch center which has a huge tower, and another one in north harrison county. So they don't seem to be complaining too much about signal. I just wish it wasn't provoice.