The 90s were a wonderful time for portable communications devices. Cell phones had mass, real buttons, and thick batteries – everything you want in next year’s flagship phone. Unfortunately, Zach Morris’ phone hasn’t been able to find a tower for the last decade, but that doesn’t mean these phones are dead. This weekend at Shmoocon, [Brandon Creighton] brought these phones back to life. The Motorola DynaTAC lives again.
[Brandon] has a history of building ad-hoc cell phone networks. A few years ago, he was part of Ninja Tel, the group that set up their own cell phone network at DEF CON. That was a GSM network, and brickphones are so much cooler, so for the last few months he’s set his sights on building out a 1G network. All the code is up on GitHub, and the hardware requirements for building a 1G tower are pretty light; you can roll your own 1G network for about $400.
The first step in building a 1G network, properly referred to as an AMPS network, is simply reading the documentation. The entire spec is only 136 pages, it’s simple enough for a single person to wrap their head around, and the concept of a ‘call’ really doesn’t exist. AMPS looks more like a trunking system, and the voice channels are just FM. All of this info was translated into GNU Radio blocks, and [Brandon] could place a call to an old Motorola flip phone.