Time signals?

[Gees]

In the pub the other night we got to talking about the BBC "Pips" time signals as put out on radio 4 and the like. Question is Which ones are the Accurate ones. Is the the normal terrestrial pips or the satellite pips ( delayed of course). Do the BBC take this into account when useing satellite transmission?

 

[FDJ]

Source:
http://en.wikipedia.org/wiki/Greenwich_Time_Signal

Accuracy

The pips for national radio stations and some local radio stations are timed relative to UTC, from an atomic clock in the basement of Broadcasting House synchronised with the National Physical Laboratory's Time from NPL and GPS. On other stations, the pips are generated locally from a GPS-synchronised clock.

The BBC compensates for the time delay in both broadcasting and receiving equipment, as well as the time for the actual transmission. The pips are timed so that they are accurately received on long wave as far as 160 kilometres (100 mi) from the Droitwich AM transmitter, which is the distance to Central London— the speed of light being pretty much irrelevant for these purposes (and, in any case, unavoidable).

Newer digital broadcasting methods have introduced even greater problems for the accuracy of use of the pips. On digital platforms such as DVB, DAB and the Internet, the pips — although generated accurately — are not received by the listener exactly on the hour. The encoding and decoding of the digital signal causes a delay, usually between 2 and 8 seconds. In the case of satellite broadcasting, the travel time of the signal to and from the satellite adds about another 0.25 seconds.

 

[ericmark]

Most computers take time to process and many TV's now have mini computers built in. Most use a special cut down version of linux so the delay is not as much as with a full blown PC.

However if you run two satellite receivers for example Sky and Free to Air you will notice watching the same program from same source there can be quite a delay one to other.

Audio systems also have built in delays when using 5.1 etc so again the receiving equipment introduces the delay not the transmitter.

Many clocks built into equipment don't use long wave but use RDS on VHF or even the teletext on TV to correct the time.

With the analogue TV being turned off soon there will I am sure be items of equipment which will no longer be able to update it's time. My VCR and DVD recorder I am sure will have this problem. There seems to be nothing available to locally generate these signals.

Also my mobile auto corrects date and time and so does my house land line phone and I am sure there will be a few seconds difference in them.

I know one place I worked we realised the time clocks for clocking in could be out by up to 2 minutes so the firm allowed you to be two minutes late or early clocking to allow for this.

But years ago we never seemed to be so pre-occupied with time and quarter of an hour plus or minus was close enough. Ever since Wordsworth we seem to have been getting more time controlled.

However it's time for bed said sleepy head.