Mystery of the missing pip: BBC admits digital listeners get five, not six

‘When an extra programme comes on, we have to squeeze the remaining space up a bit’

FOR NIGH on a century, the BBC radio pips have been a reassuring sound for listeners across the world. But recently there has been a sinister development: the disappearance of the final pip.

If you have tuned in to Today, you might have thought you were imagining the fact that you can hear five pips instead of six. However, the BBC has confirmed that it really does go astray – but only for those listening on DAB radios. For technical reasons, broadcasts are sometimes muted for a second, and often this happens on the stroke of 8am.

The mystery of the missing pip was solved by Paul Grimsdell, a BBC engineer at Broadcasting House.

He answered a query from Gordon Robertson of Dundee, a Daily Telegraph reader who wrote to the Letters page asking: “Have any other Radio 4 listeners noticed a recent disturbing omission on the sixth, longer pip on the hour?

“This can happen at various times of day, but it appears to have become a frequent feature at 8am during the

Today programme.”

Mr Grimsdell provided the explanation. When programmes are added to the long-wave service – for example, Test Match Special, Yesterday in Parliament or the Daily Service – then space on the airwaves must be rearranged. “The amount of programming we can put into DAB is technically limited. When an extra programme comes on, we have to squeeze the remaining space up a bit.

“When we make one of these changes, a DAB radio will have to adjust

and it takes a brief moment to do that, which involves a short mute.

“Yesterday in Parliament begins at 8.31am but we don’t want to make the change then because it would occur in the middle of a programme and that would be disruptive. Instead, we reconfigure at 8am, which is why those pips in the Today programme might be briefly affected.”

Mr Grimsdell added that whether or not a listener hears abbreviated pips will depend on the make and model of the radio. Those listening on FM or via Freeview will be unaffected.

The pips were first heard on Feb 5 1924, introduced at the suggestion of Frank Watson Dyson, the then Astronomer Royal.

Officially known as the Greenwich Time Signal, the six pips were once the same length: each one-tenth of a second. The elongated final pip, lasting half a second, came into being in 1972.

SIR – Gordon Robertson (Letters, December 16) wonders why the sixth, longer pip on the hour is occasionally omitted on BBC Radio 4, particularly at 8am during the Today programme.

I would hazard a guess that he is listening on a DAB radio. The space available for each network in the DAB “multiplex” (in layman’s terms, a lump of frequencies) is limited by technical considerations, with more space allocated to the more demanding networks – stereo and best quality to Radio 3, mono and lower quality for some speech-only networks.

Space is reassigned as needed as networks enter and leave the multiplex. The allocations are often rearranged at 8am to make space for Yesterday in Parliament at 8.31am. The brief muting of Mr Robertson’s radio is caused as the internal gubbins takes note of the long-wave Radio 4 programme stream becoming available. Times for changes are chosen to try to minimise disruption to programme content.

The abbreviated pip is only on DAB, and will depend on variables including the make and model of radio. The full 500 milliseconds of the last pip are still available on all other platforms, such as FM or Freeview. Paul Grimsdell

BBC Engineer

BBC Broadcasting House London W1