Are they the same decibel rating? When it comes to the UHF aerials, the decibel rating determines their range and effectiveness. Check this out to explain the differences... Firstly let's look at Gain - If you look at the diagram below, with the vertical line representing the antenna, the outer circles indicates how the signal is transmitted with various gain antennae. In summary the higher the gain the more direct and pinpoint the signal, thus longer distance but far less 'rollover' effect, consequently reducing performance in hilly areas. The diagram below typically shows what happens to the signal between two vehicles - note how the signal with a 3db gain antenna actually reaches the second vehicle s antenna but the 6db does not Ideally if would be advantageous to change antennas when in flat country and also when in hilly country - This situation is certainly not ideal, so a compromise is the only answer - In summary the best all-round choice is 4.5-6db Hope that helps mate.