That is a difficult question to answer without knowing where you live. If you were to take a helicopter ride above downtown Columbus, it actually sits in a shallow bowl nearly surrounded by higher terrain. This will pose serious problems when trying to receive signals higher in frequency than the VHF bands at distances beyond 30 miles or so. Can you receive the Columbus DTV UHFchannels with an attic antenna? If you can receive them clearly then you may have a chance if you use a Yagi type 800 MHz scanner with high gain in the desired direction. If you can't receive any DTV UHFchannels, then forget about trying to receive trunked stuff. .
W8JNC