The SDR revolution has completely changed the way radio enthusiasts pursue their hobby, but there is still a space for the more traditional scanning receiver. If you are an American, have you ever noticed that it has a gap in its coverage between 800 and 900 MHz? The curious reason for this is explored by [J. B. Crawford], and it’s a tale of dusty laws relating to a long-gone technology, remaining on the books only because their removal requires significant political effort.
What we might today refer to as “1G” phones used an entirely analogue transmission scheme, with an easily-receivable FM carrier for the voice and extremely low-bandwidth bursts of serial data only for the purposes of managing the call. Listening to these calls was an illegal activity, but for those with the appropriate scanners it became a voyeuristic hobby within a hobby. It even made the world news via the pages of the gossip sheets, when (truthfully or not) it was credited for the leak of a revealing and controversial conversation involving Diana Princess of Wales.
This caused significant worry to the cellular phone companies who understandably didn’t want their product to become associated with insecurity. Thus they successfully petitioned the US Congress to include a clause restricting the capabilities of scanning receivers into another telecoms-related Act, and here we are three decades later with analogue phones a distant memory and the law still on the books. It may be ancient and unnecessary but there is neither the will nor the resources to remove it, so it seems destined to become one of those curious legal oddities that remains on the books for centuries. Whether an RTL-SDR breaks it is something we’ll leave for the lawyers, but the detail in the write-up makes it well worth a read.
Header image: krystof.k (Twitter) & nmuseum, CC BY-SA 3.0.