Distributed FM radio from a single digital signal

There’s currently no plan to switch off FM stations. In fact, many radio bosses have said oh, for heaven’s sake to the very idea. There is, astonishingly, less of a plan for radio switchover than there is desire among the general public for TV switchover. So that must be some sort of record for nothingness.

Seriously: who among us is just itchy and fidgety, waiting for analogue TV signals to be switched off? Who wakes up of a morning thinking, ooh, Whitehaven have to buy Freeview boxes now! with a frisson of glee? Radio switchover would be even more disastrous, of course: whereas TVs normally have a gap between themselves and an aerial into which to insert a Freeview box and convert digital to analogue, most radios are monolithic: receiver, “decoder” and audio equipment all together. That means that the average of five radios per household would be simply landfill material, useless fizzing boxes capable of picking up nothing but static. Future generations will already find a sliver in the geological strata that they can classify as “analogue to digital”; FM switchoff would add a shiny, plasticky laminate to that layer.

Here’s a thought, though: how about a little digital-to-analogue converter for radio? It could be the size and construction of, say, a Fon, and configurable over USB. It would transmit FM in the style of an iTrip to fill perhaps the room it’s kept in, plus neighbouring rooms. It could transmit multiple FM stations at the same time, and even mimic the frequencies of the analogue stations (if they were ever, say, switched off without anyone wanting them to be: God forbid!)

But what if your converter’s chosen frequencies conflict with next door? FM transmission depends on phase coherence, so even if your two boxes were within an electronic ace of each other frequency-wise, they’d still interfere with each other and cause all sorts of beating, flangeing and other dirtily-named auditory confusion. At least when someone passes you on the motorway and their phat BMW iPod transmitter briefly swamps yours then they’re gone quickly, hopefully to come to some sort of messy grief on the next bend. But if you’re stuck near someone who permanently foxes your radio listening—and it would only take maybe three or four such converters for a conflict to be inevitable in the narrow FM band—then what do you do?

Answer: let the converter boxes know how to talk to each other. Let them negotiate their frequency spreads. Let them, moreover, report back to you over what sort of understandings you and your neighbour’s radios can come to. Let them synchronize, if possible, on stations you both want to listen to, strengthening the signal and meaning both of your houses are entirely covered by the FM cloud. Exploit, don’t squash, the wisdom of the group.