BBC Greenwich Time Signal inaccurate

John_Gray

PasturesNew wrote: »

I bought a radio controlled clock from a car boot - best thing ever. One clock that actually tells the right time (most of the time).

What you are talking about is not actually a radio-controlled clock!

The clock adjusts itself about midnight each day using the low-frequency time-signal from Anthorn in the Lake District or from Mainflingen, Hessen, located southeast of Frankfurt am Main, if it's a German make from Aldi or Lidl.

It's unlikely to lose or gain many seconds during the day, but it's possible.

50Twuncle

John_Gray wrote: »

What you are talking about is not actually a radio-controlled clock!

The clock adjusts itself about midnight each day using the low-frequency time-signal from Anthorn in the Lake District or from Mainflingen, Hessen, located southeast of Frankfurt am Main, if it's a German make from Aldi or Lidl.

It's unlikely to lose or gain many seconds during the day, but it's possible.

We have 3 such clocks in the house and all are perfectly in sync with each other and also with "internet time" from my PC - So it is just BBC time that is out of sync !!

John_Gray

50Twuncle wrote: »

We have 3 such clocks in the house and all are perfectly in sync with each other and also with "internet time" from my PC - So it is just BBC time that is out of sync !!

No - earlier it has been mentioned that the time given by the BBC on an FM radio is correct. When produced on a DAB radio, the time signal pips are slow by the time taken for the digital signal processing to take place on that particular radio - they vary according to the circuits they employ: most of mine take around 2½ seconds, so the pips are about 2½ seconds later than on my FM radios.

coffeehound

John_Gray wrote: »

When produced on a DAB radio, the time signal pips are slow by the time taken for the digital signal processing to take place on that particular radio - they vary according to the circuits they employ: most of mine take around 2½ seconds, so the pips are about 2½ seconds later than on my FM radios.

2.5 seconds to process an audio signal? Really? I presumed the delay was mainly at the broadcasters end.

John_Gray

There will be some effect at the transmitting end, you're right, unless the broadcasters attempt to correct for it by broadcasting a recording of the pips "early" - I don't believe the BBC does this, unfortunately.

Hence the best time sources are atomic clocks (if you have one!), "TIM", radio-corrected clocks, an ordinary quartz wrist-watch, PC time adjusted using the Network Time Protocol (NTP) [usually weekly, but it can be made daily using a registry edit].

In most circumstances, an error of a few seconds is irrelevant!

wongataa

coffeehound wrote: »

2.5 seconds to process an audio signal? Really? I presumed the delay was mainly at the broadcasters end.

It takes time at the broadcaster's end to encode the radio signal into DAB and then broadcast it. It takes time at the receiver's end to decode the DAB signal and play the results through the speaker. It can take longer than you think. The delay at the receiver's end will depend on what is doing the decoding.

prosaver

I remember the clock on the car park ticket machine was 5 minutes fast and nearly got caught out.
Btw if you put a analogue radio on and the digital radio on at the same time the digital ones about 2 seconds out.
use to happen with the free view TVs when the old aerial TV was still going.

also the live football TV is about 30 seconds out than the radio,

maybe I should go out more?

agrinnall

You sometimes notice it when driving and listening to a DAB station, as you switch between transmitters you get a few seconds of the programme repeated (or I assume lost, although I've never noticed that).

forgotmyname

agrinnall wrote: »

You sometimes notice it when driving and listening to a DAB station, as you switch between transmitters you get a few seconds of the programme repeated (or I assume lost, although I've never noticed that).

Thats probably old age rather than the radio

kwikbreaks

50Twuncle wrote: »

So - is terrestrial TV time signal correct ?

I doubt it's accurate to the second. If I watch BBC News on HD It makes me switch to SD to see the local news so I switch during the weather forecast and going from HD to SD always leads to a short repeat for me despite the box taking a second or two to lock in the new channel. I see the same thing on both Freeview here and with Freesat at home so the delay must be with the BBC.