Thats self-defeating. Phased transmitters are more expensive, but impossible to discover without wall penetrating radar, sonar or EM induction scanners, none of which are used.
However, if you can find one node, you can use that node to discover other nodes by signal strength and direction analysis(you need to be pretty near a node to distinguish it from general radio noise in a city though)...thats without a Tinker, though in town its just Squealer, Leet, Kid Win and Armsmaster with specialties that can be applied to reverse trace the network.
Phased is a total obscurity strategy, we spread more slowly, but its basically impossible to find unless you're specifically looking for it. And even then its quite a bit of work to search.
Regular transmitters basically bank on getting coverage up fast enough to outpace the random discovery.