Time Signals

Old Jul 16th 2011, 5:02 pm
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Default Time Signals

...are now a joke.

In the UK they seem to come in this order:
FM radio
Freesat TV
DAB radio
Internet TV

Here it's Spanish radio
Spanish TV
English radio station in Canaries
internet radio
internet TV

Does anyone know if Movistar have a speaking clock?
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Old Jul 16th 2011, 5:53 pm
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Default Re: Time Signals

Well if they do it will cost you a bleeding fortune
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Old Jul 16th 2011, 6:13 pm
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Default Re: Time Signals

Check the time on a GPS - it will be more accurate than any other available source.
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Old Jul 17th 2011, 7:51 am
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Smile Re: Time Signals

Originally Posted by Fred James
Check the time on a GPS - it will be more accurate than any other available source.
We have a weather station with clock which takes its time from the European Standard clock in Frankfurt so I set all the clocks to that but I will check it against my sat nav for the GPS time. Wonder which is correct?
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Old Jul 17th 2011, 10:52 am
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Default Re: Time Signals

Originally Posted by John & Kath
We have a weather station with clock which takes its time from the European Standard clock in Frankfurt so I set all the clocks to that but I will check it against my sat nav for the GPS time. Wonder which is correct?
But your weather station clock must get a signal from Frankfurt by satellite, no?
So therefore another delay of some kind.

Nearest I have got is listenting to the UK Pips over the telephone.

Satnav in Lanzarote ????? The island is only 42 miles by 17. I defy ANYONE to get lost!
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Old Jul 17th 2011, 11:15 am
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Default Re: Time Signals

Originally Posted by Rostra
Satnav in Lanzarote ????? The island is only 42 miles by 17. I defy ANYONE to get lost!
Yes but many phones now have a GPS in them - even my camera has one!
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Old Jul 17th 2011, 11:26 am
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Default Re: Time Signals

Originally Posted by Rostra
But your weather station clock must get a signal from Frankfurt by satellite, no?
No it's a radio signal which travels at about 186,282 miles per second which should make the clock reasonably accurate.
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Old Jul 17th 2011, 11:28 am
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Default Re: Time Signals

Originally Posted by Fred James
Yes but many phones now have a GPS in them - even my camera has one!
Ahh, yes, but you are talking 'Up To Date Technology' here (otherwise known as Toys for Boys). Thats another for me.

I have phones which are phones, cameras which are cameras and internet on my computer/s.

Call me a Dinosaur ... (sigh)
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Old Jul 17th 2011, 11:29 am
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Default Re: Time Signals

Originally Posted by Fredbargate
No it's a radio signal which travels at about 186,282 miles per second which should make the clock reasonably accurate.
That should be good enough!
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Old Jul 17th 2011, 11:38 am
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Default Re: Time Signals

Originally Posted by Fredbargate
No it's a radio signal which travels at about 186,282 miles per second which should make the clock reasonably accurate.
It's all relative. The GPS clock is accurate to 14 nanoseconds. It takes 5 million nanoseconds for the signal to get from Frankfurt to southern Spain.
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Old Jul 17th 2011, 12:56 pm
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Default Re: Time Signals

Over the past 10 years there has been a surge in Radio Time Clocks that use live radio signals and then convert to a digital time display and prices have fallen drastically when compared with the original Heathkit launched in 1983 and costing $250 kit or $400 assembled.

Accurate time signals should be possible from live on air radio transmissions from for example BBC World Service, on Short Wave, as they send out the pips on the hour (well 22 out of the 24 – the other 2 use Big Ben)

There are Spanish radio stations on FM that also send out pips, generally 2, not the 6 used by the UK but I have not yet carried out an actual check on their accuracy. Before posting this I have checked Oasis FM on line and they didn’t put out pips at 1300.

The NPL in Teddington replaced the original MSF transmissions from Rugby on 60khz in 2007 for a commercial transmission on same frequency from GBZ located in Cumbria. However, the output is lower and will not be received over such a long distance.
The PBT time transmission is on 77.5khz from Mainflingen, Germany as referred to by Fred is well known and there is a French TDF transmission on 160khz from Allouise, a wacking great signal but all these use variations of BCD transmission which needs a decoder to give you the actual time and most of the frequencies are not available on retail radios.
All these stations are not just time but also accurate frequency transmissions for other purposes.

As Fred says, if you have GPS that is an accurate way of doing it, the more satellites it picks up the more accurate. This is original 1960’s technology for nuclear submarines and due to US restrictions on use\accuracy the EU is spending €billions on the Galilleo Project to give “the free world” an alternative – probably with similar restrictions.
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Old Jul 17th 2011, 1:13 pm
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Default Re: Time Signals

Originally Posted by Domino
As Fred says, if you have GPS that is an accurate way of doing it, the more satellites it picks up the more accurate. This is original 1960’s technology for nuclear submarines and due to US restrictions on use\accuracy the EU is spending €billions on the Galilleo Project to give “the free world” an alternative – probably with similar restrictions.
Digressing slightly, GPS accuracy is pretty good now.

I had one of the first GPS navigators on my boat over 20 years ago and the accuracy was deliberately downgraded by the US military as it turned out that the commercial versions were giving military accuracy - not what was intended.

They introduced a timing "wobble" to reduce accuracy to about 100m. Then the Gulf war stated and the military had a shortage of receivers so they had to buy up almost the whole stock of commercial receivers and turn off the "wobble". Overnight we found we had almost 1m accuracy.

It did get turned on again eventually but some time ago they gave in to popular demand and turned it off again which is why we now have such an accurate system.
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Old Jul 17th 2011, 1:30 pm
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Default Re: Time Signals

Originally Posted by Fred James
Digressing slightly, GPS accuracy is pretty good now.

I had one of the first GPS navigators on my boat over 20 years ago and the accuracy was deliberately downgraded by the US military as it turned out that the commercial versions were giving military accuracy - not what was intended.

They introduced a timing "wobble" to reduce accuracy to about 100m. Then the Gulf war stated and the military had a shortage of receivers so they had to buy up almost the whole stock of commercial receivers and turn off the "wobble". Overnight we found we had almost 1m accuracy.

It did get turned on again eventually but some time ago they gave in to popular demand and turned it off again which is why we now have such an accurate system.
ISTR they had to "work round it" when putting the rigs into the North Sea

all the ships I was on used LORAN but thats a radio based system based on the principle of the time difference between the receipt of signals from a pair of radio transmitters. GPS has almost pushed this out of business but it is now being looked at as a standby alternative to GPS.
Loran uses the same frequency spectrum as the vlf time/frequency signals.
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Old Jul 17th 2011, 2:17 pm
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Default Re: Time Signals

Originally Posted by Domino
ISTR they had to "work round it" when putting the rigs into the North Sea

all the ships I was on used LORAN but thats a radio based system based on the principle of the time difference between the receipt of signals from a pair of radio transmitters. GPS has almost pushed this out of business but it is now being looked at as a standby alternative to GPS.
Loran uses the same frequency spectrum as the vlf time/frequency signals.
There was a "work around" for some time called "differential GPS. That worked by a fixed land station with an exactly known location, receiving the GPS position, comparing it to the actual position and then transmitting the "error" by radio to the special DGPS receiver which corrected their received signal using the broadcast error hence getting the true position.

It only lasted for a couple of years before the US turned off the wobble and the DGPS receivers became redundant.

There are special techniques for averaging out the received position to get a more accurate position.

You mention LORAN. I never tried that but in the 80's I had a small yacht version of the Decca Navigator - like the system the fishermen used and that was very good - better than the alternative "Satnav" system that existed at the same time.

Interesting memories!
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Old Jul 17th 2011, 2:33 pm
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Default Re: Time Signals

Originally Posted by Fred James
There was a "work around" for some time called "differential GPS. That worked by a fixed land station with an exactly known location, receiving the GPS position, comparing it to the actual position and then transmitting the "error" by radio to the special DGPS receiver which corrected their received signal using the broadcast error hence getting the true position.

It only lasted for a couple of years before the US turned off the wobble and the DGPS receivers became redundant.

There are special techniques for averaging out the received position to get a more accurate position.

You mention LORAN. I never tried that but in the 80's I had a small yacht version of the Decca Navigator - like the system the fishermen used and that was very good - better than the alternative "Satnav" system that existed at the same time.

Interesting memories!

DNS was the commercialisation of the original GEE system of WWII on which the Yanks based their Loran
remember listening to "fish-tones" on my receiver

have lived and breathed all these things since before leaving school in early 60's.
problem is the youngsters (and oldsters) of today are only interested in opening a box and switching it on, no concept of how it actually works, or how old some of this "leading edge technology" is.
Its only the miniaturisation that has allowed these things to leave the military and big business.
Remember visiting BBC at Brookmans Park and standing next to the transmitter valves which were over 6ft high.
Only a few years later I was making pcb's for the "bleep tone" as used in the Apollo program, where they used slide rules and not pc;s to get to the moon
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