No interoperable digital voice standard — D-STAR, DMR, Fusion, P25 are all incompatible

Amateur radio has four widely-deployed digital voice systems — D-STAR (Icom), System Fusion (Yaesu), DMR (multiple manufacturers), and P25 (public safety crossover) — and none of them can talk to each other natively. Who has this problem? Every ham operator who buys a digital radio and discovers they can only talk to other operators using the same system. So what? A ham with a $500 Yaesu FT-5D (Fusion) cannot communicate with a ham using a $300 Icom ID-52A (D-STAR) or a $150 Anytone AT-D878 (DMR), even if they are on the same frequency. So what? Clubs and regions fragment along manufacturer lines — the local repeater is Fusion, but the regional emergency net uses DMR, requiring operators to buy multiple radios. So what? During emergencies requiring interoperability between different amateur groups, digital voice becomes a liability rather than an asset, and operators fall back to analog FM. So what? The entire investment in digital repeater infrastructure (tens of thousands of dollars per system) provides less interoperability than the analog FM system it replaced. Why does this persist? Each manufacturer (Icom, Yaesu, Kenwood) uses digital voice as a proprietary lock-in strategy to sell radios. There is no regulatory requirement for interoperability in Part 97. Cross-mode bridges (like AMBE-based transcoding systems) exist but add latency, cost, and points of failure. The amateur community has been unable to agree on a single open standard because each system has an entrenched user base that resists migration.