The 470 to 512 MHz band carries police, fire and EMS radio systems in a small number of the country's largest metropolitan areas, and for nearly nine years federal law required those agencies to leave it. Congress repealed that requirement in December 2020, by which time the FCC had frozen [...]

Encryption on a P25 or DMR system is applied one transmission at a time by the radio that is talking, which means a talkgroup is only as secure as its worst-programmed portable. When a single radio goes out in the clear, the audio sounds exactly the same to everyone else [...]

A storefront in McAllen, Texas that sold two-way radios and installed car alarms was, according to federal court records and press reporting, the design office for one of the largest privately built radio networks in the hemisphere. The technical lessons in that case are ordinary land mobile... [...]

A vehicular repeater is one of the few tools that genuinely solves the talk-in problem, because it moves the hard part of the radio path from a five watt handheld on a firefighter's chest to a roof mounted antenna twenty feet away. That is real engineering and it works. What [...]

A subway bore can carry a radio signal farther than free space would and still leave a crew cut off two hundred feet in. The tunnel is a waveguide with a temper, favoring some frequencies, punishing curves, and going dark the moment a train fills the cross section. The engineered [...]

A portable that works fine on a parking lot drill can fail completely on the twentieth floor of a concrete office tower, and that failure is not a defect, it is physics doing exactly what it is supposed to do. Reinforced slabs, metallized glass, and a masonry stair shaft are [...]

For most of the First World War the most reliable way to get a written message out of a forward position and back to a headquarters was a bird. That is not a charming footnote, it is an engineering result. The wireless of the day was heavy, fragile, power hungry, [...]

Coverage on the third floor tells you nothing about coverage under the first one. A firefighter who has been talking to command all morning falls through a weakened floor into a basement, and the portable that worked upstairs now has to reach a repeater site miles away through a floor [...]

On the night of 14 April 1912 the ship closest to the sinking Titanic had a working wireless set, a licensed operator, and no one wearing the headphones. The operator had shut the station down and gone to bed. That is not a technology failure. It is a watchstanding failure, [...]