A larger antenna and/or more power out would work. As far as i know, UHF frequency range is mostly line of sight, so any obstructions are going to dramatically reduce range. If there are a lot of things in the way, more power out is not going to do much (may get you through some trees). A larger antenna (can be anything from aluminum foil to a piece of wire or a high end manufacturer) on either the Rx side or the Tx (or both) would allow larger coverage to rcv/xmit the signals. That's probably the easiest route before tinkering with the internals. There are equations for the size of the antenna in regards to wavelength and frequency. Trial and error works too. If i were to start messing with an antenna, i would use the Rx side first. But i also agree with alfacliff and Papabravo.