BBC Greenwich Time Signal inaccurate

We agree that the lag is a problem?
Surely what we are discussing here (off at a tangent a bit) is the cause of any lag producing a delay?
I might be missing something but I don't follow your argument that it is the carrier speed (only) that is the issue.
Rather I see that as a potentially contributory factor given that several coded time systems can use different carriers and result in virtually the same or similar accuracy and in other cases cannot; but if you have a download speed that causes a delay to transmit a data packet (that contains coded time) that cannot be accurately quantified (i.e. a variable and unknown lag) then it is impossible to get accurate time from that irrespective of the carrier used. In relative terms the longer the delay compared with the desired accuracy the bigger the problem!
It would be good if you could expand on your disagreement uncle. Are we just looking at the ' lag ' from a different perspective or am I missing something -apart from brain cells:)

Running a local ntpd server syncing to multiple pool servers around the world should do a fair job of countering communication latency. I used to do that for my local network until Windows built in the ability to ntp sync the clock.

My clock radio syncs to the NPL signal but only once, when powered on. It has drifted by about four minutes since then, which means I'm now woken up by the radio 4 weather, not the pips!

prosaver wrote: »

i thought terrestrial tv was the old analog system then they stopped it and now we have digital free view....

Terrestrial TV - analogue or digital - comes from transmitters on 'terra firma'; on the ground.

As opposed to satellite, which doesn't.

Almost all the timepieces I have adjust themselves to the time signal, GPS or via the internet and all of them sinc to the second.

I'm not really sure what the purpose of the the BBCs clock/pips is these days now there are much better time sources available. Seems like an archaic idea well past its use by date - much like the BBC itself in many ways.

Ah I see that you mean the carrier speed is (virtually) constant and very fast (in the case of the electromagnetic spectrum -ignoring minor changes that do take place through various mediums)....And that it is the only factor affecting speed and thus lag comes from another cause such as the turn round time via satellites?

Now carrier speed is independent of frequency however time information (as distinct from frequency/time period of wavelength that produces a clock frequency) usually is modulated onto the carrier as a word (of differing lengths depending on the coding, complexity of message and housekeeping information) and at a range of modulation rates.
This as an analogy consider transmissions using light/radio telegraphy or waves-we will for the purpose of the discussion accept a constant speed will we not? - then tell me if the rate of transmission varies and hence the delay with the following methods to send a message:
Ships flags
Semaphore
Aldis lamp
Telegraph
AM radio transmission
Digital signal transmission down lines such as ADSL
Fibre optic digital comms.
Satellite transmissions such as GPS and similar?

Are they all equal?

Now there are differences in overhead and housekeeping, complexity of information length but all have differing rates at which the data can be transmitted such as how fast one can key/send the data.
All these are analogous to rate of transmission and upload/download speeds. Therefore it is a factor which is what I maintained and you disagreed with.

There are many a time code systems that find that speed a problem or irrelevant. Those that do use methods to overcome . From my hazy memory SMPTE code might not but IRIG codes do. These are coded words modulated onto electromagnetic carriers and use correction/markers to compensate for the time to load the information resulting from the various transmission rates (albeit small) that is not different to a download rate.

Must admit though that I do not have a full answer to the long delays you mention but guess it must be processing and comments error correction times.

Maybe interesting to note GPS positioning relies on not different modulation rates but time differences receiving the carrier data from a number of satellites so these ever so small delays we think of possibly as irrelevant are put to good purpose!