A two-way radio system using a repeater may have great coverage except in areas, such as parking garages and basements of buildings, whose environmental factors create stubborn “dead” spots. In these locations, the repeater signal reaches the radio, but the handheld cannot reach back to the repeater. The traditional solution to this problem is to add Bi-Directional Amplifier and Distributed Antenna System within the building. Although this is a proven approach to get signals into problem areas, it can be complicated and costly. The complication comes from ensuring the signal is not overlapping the original in a manner that interferes with itself. The costliness is due to the need of running antenna coaxial cable from the amplifiers to the trouble zone, which may require many feet of cable and possible drilling through walls.
When there’s a need to extend the coverage of handheld two-way radios, the first option is usually a repeater. However, a repeater isn’t the full answer. A repeater will typically put out much more power and have a better antenna system than the portable radios with which it is communicating. This presents an unbalanced system where the transmit power of the repeater reaches much further than the transmit power of the handhelds.
Couldn’t this be resolved by turning the power of the repeater down to match the handheld? The reality is that often times mobile radios installed in vehicles and handheld radios are in use on the system. Mobile radios typically have greater transmit power than handhelds. Reducing the repeater power output to match the lowest powered device – the handheld – significantly constrains the system coverage, making the usable radius of the system much less than what it could be.