I have a digital radio next to my bed (it's actually the one that used to be in the kitchen, until the volume knob became temperamental - you know how it goes). At 6am each day it switches on BBC Radio 4 - the "Today" programme on weekdays - so that I may update myself on the latest glories of Brexit and Trump and all the other things which guarantee that I may start my day as depressed as possible. At 7am it switches off - the assumption being that either I'm already up and functioning, or else I have probably had enough delight and happiness for one morning.
The reality, of course, is that I have set the menu on the radio so that BBC R4 will come on at 06:00 and switch off at 07:00. The radio knows what time it is because the exact time is transmitted constantly along with the programme signal - so you would expect that to be pretty accurate. I mean, we are speaking of the speed of light here.
Astonishing, really - in the digital age we just expect everything to be spot on. It's worth remembering that it was only the coming of the railways which necessitated some standardisation of clocks throughout Britain, and, before that, the coming of scheduled stagecoaches was a big push towards standardisation of the calendar - prior to that it didn't matter a huge amount if your village had a different date from the village down the road. Now we have so much accuracy we can't even remember why it's important.
I digressed there - sorry.
The point of my post is that each morning the radio switches itself off just as the "pips" of the time signal are being broadcast. I don't know much about the pips, really, except that they've always been part of listening to the radio - even when it was a wireless. Six pips - 5 short ones and a long one - like this...
Originally, I think these were generated by the Greenwich observatory, but for the past 30 years or so they have just been a service provided by the BBC - they are timed exactly so that the long final pip indicates the start of the next hour.
|Here's the 8am signal - impressively accurate|
A couple of seconds is near enough for me, of course, but I don't really see how this works. Is it possible that there is some buffering or delay in the programme transmission? - I have occasionally noticed that if you switch two DAB radios to the same station they may not be quite in sync - this is especially true, I find, if you listen to the digital radio service on your TV at the same time as the same station is connected via the DAB unit.
Anyone understand how this works? Is it possible that the BBC are going to the trouble of broadcasting an exact time signal which isn't actually accurate by the time it reaches the listener? Imagine the potential chaos - stagecoaches could be crashing into each other at crossroads all over the country.
|It'll all end in tears|
Anyone know how this works?