Compared to 6.25 kHz FDMA, two-slot TDMA allows you to achieve 6.25 kHz equivalent efficiency while minimizing investments in repeaters and combining equipment. This is one reason why TDMA is so well suited to professional applications, where the budget for two-way digital radio may be limited compared to the mission-critical tier.
FDMA requires a dedicated repeater for each channel, plus expensive combining equipment to enable multiple frequencies to share a single base-station antenna. It can be particularly expensive to make combining equipment work with 6.25 kHz signals, and there’s typically a loss in signal quality and range when it’s used this way.
In contrast, two-slot TDMA achieves two-channel equivalency using single-channel equipment. No extra repeaters or combining equipment is required.
