UK [DAB] radio disturbance caused by satellite network bug

http://www.bbc.co.uk/news/technology-35463347

This means that the whole UK DAB radio network is dependent on GPS provided by the grace and favour of the USA.

WTF were they doing anyway - terrestrial radio transmitters don't move so once you have their locations accurately ONCE you can lock them all together (phase / frequency) repeatably using the same parameters.

On 02/02/2016 16:18, R. Mark Clayton wrote:
http://www.bbc.co.uk/news/technology-35463347

This means that the whole UK DAB radio network is dependent on GPS provided by the grace and favour of the USA.

WTF were they doing anyway - terrestrial radio transmitters don't move so once you have their locations accurately ONCE you can lock them all together (phase / frequency) repeatably using the same parameters.

GPS is used as the timing reference to keep the SFN synchronised, you
need a continuous (more or less) common reference supplied to all
transmitters.

What surprises me is why only the Beeb network was the only one
affected, all DAB networks and gazillions of other systems use GPS,
yet they weren't (?) affected.


--
Mark
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On Tuesday, 2 February 2016 16:35:47 UTC, Mark Carver wrote:
On 02/02/2016 16:18, R. Mark Clayton wrote:
http://www.bbc.co.uk/news/technology-35463347

This means that the whole UK DAB radio network is dependent on GPS provided by the grace and favour of the USA.

WTF were they doing anyway - terrestrial radio transmitters don't move so once you have their locations accurately ONCE you can lock them all together (phase / frequency) repeatably using the same parameters.

GPS is used as the timing reference to keep the SFN synchronised, you
need a continuous (more or less) common reference supplied to all
transmitters.

Yes. The transmitters are on the ground. Once you have determined their position (perhaps using GPS) then you can keep them in synch relative to each other using PLL or similar - surely.


What surprises me is why only the Beeb network was the only one
affected, all DAB networks and gazillions of other systems use GPS,
yet they weren't (?) affected.

Perhaps they don't use GPS dynamically. Four satellite GPS receivers would get confused if the dud satellite was in their constellation. More modern ones tracking up to twelve satellites would not. This includes recent phones.

GPS can be disrupted for other reasons. The captain of HMS told me that back during the run up to the gulf war, he sent his purser into Pireas to buy a GPS set. Then commercial sets were only C/A (100m) and cost $$$$. When the Gulf War actually kicked off the GPS set showed that his ship had moved two miles. Fortunately the Royal Navy knows a thing or two about navigation so they weren't phased nor lost.


--
Mark
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Martin wrote:

Mark Carver wrote:

What surprises me is why only the Beeb network was the only one
affected, all DAB networks and gazillions of other systems use GPS,
yet they weren't (?) affected.

Russia and EU/ESA also provide GPS satellites.

Many smartphones seem to have GLONASS support, but Galileo isn't
switched on yet, is it?

I can see that an SFN would notice a 12ms glitch, I've had several
occasions with 15 bars of signal strength but all of a sudden I get
boiling mud for a few hours which I assume are due to timing faults, but
many users wouldn't notice a few ms, one customer who uses a GPS clock
didn't realise it have been running unsynched for over a year!

On 02/02/2016 17:20, R. Mark Clayton wrote:

need a continuous (more or less) common reference supplied to all
transmitters.

Yes. The transmitters are on the ground. Once you have determined their position (perhaps using GPS) then you can keep them in synch relative to each other using PLL or similar - surely.

You still need a common reference though, even atomic clocks drift
relative to each other

--
Mark
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On Tuesday, 2 February 2016 17:29:34 UTC, Mark Carver wrote:
On 02/02/2016 17:20, R. Mark Clayton wrote:

need a continuous (more or less) common reference supplied to all
transmitters.

Yes. The transmitters are on the ground. Once you have determined their position (perhaps using GPS) then you can keep them in synch relative to each other using PLL or similar - surely.

You still need a common reference though, even atomic clocks drift
relative to each other

Yes indeed - a master transmitter, to which all the others synchronise adjusting their timing for the propagation delay from the master. If the master drifts - they all drift together. So again WTF were they using GPS?

For DAB the wavelength is short, but I remember driving through southern Scotland on the A7 many years ago and the beats between the English and Scottish radio 4 LW transmitters as I drove along.

--
Mark
Please replace invalid and invalid with gmx and net to reply.

"R. Mark Clayton" wrote in message
...
http://www.bbc.co.uk/news/technology-35463347

This means that the whole UK DAB radio network is dependent on GPS
provided by the grace and favour of the USA.

WTF were they doing anyway - terrestrial radio transmitters don't move so
once you have their locations accurately ONCE you can lock them all
together (phase / frequency) repeatably using the same parameters.

Thanks for the link. I suffered this outage in London (very early morning)
and was puzzled that day to find no mention on the BBC info pages (or
anywhere as far as Google was concerned). I knew it was not just me as all
my DAB receivers had no BBC except Surrey and 3Counties.

On 02/02/2016 17:35, R. Mark Clayton wrote:
On Tuesday, 2 February 2016 17:29:34 UTC, Mark Carver wrote:
On 02/02/2016 17:20, R. Mark Clayton wrote:

need a continuous (more or less) common reference supplied to all
transmitters.

Yes. The transmitters are on the ground. Once you have determined their position (perhaps using GPS) then you can keep them in synch relative to each other using PLL or similar - surely.

You still need a common reference though, even atomic clocks drift
relative to each other

Yes indeed - a master transmitter, to which all the others synchronise adjusting their timing for the propagation delay from the master. If the master drifts - they all drift together. So again WTF were they using GPS?

Name me another cheap and easy to receive timing reference signal, that
can received easily at all Tx sites from Jersey to The Shetland Islands ?

For DAB the wavelength is short, but I remember driving through southern Scotland on the A7 many years ago and the beats between the English and Scottish radio 4 LW transmitters as I drove along.

Yes, and what's that got to do with it ?


--
Mark
Please replace invalid and invalid with gmx and net to reply.

"R. Mark Clayton" wrote in message
...
http://www.bbc.co.uk/news/technology-35463347

This means that the whole UK DAB radio network is dependent on GPS
provided by the grace and favour of the USA.

WTF were they doing anyway - terrestrial radio transmitters don't
move so once you have their locations accurately
ONCE you can lock them all together (phase / frequency) repeatably
using the same parameters.

The transmitters don't move but the network feed to them may reroute
(which happens automatically and without warning) so GPS - which as
someone else said reaches all parts that even others cannot - is the
only way to ensure that the transmitter gets back in sync a.s.a.p.

Think of all those French church and town hall clocks that are running
off Allouis. What will happen to them when the Tx shuts down in 2017?
You can't use VLF/LF transmitters as a reference due to propagation
times, so GPS is the only option.



--
Woody

harrogate3 at ntlworld dot com

On Tuesday, 2 February 2016 18:56:09 UTC, Mark Carver wrote:
On 02/02/2016 17:35, R. Mark Clayton wrote:
On Tuesday, 2 February 2016 17:29:34 UTC, Mark Carver wrote:
On 02/02/2016 17:20, R. Mark Clayton wrote:

need a continuous (more or less) common reference supplied to all
transmitters.

Yes. The transmitters are on the ground. Once you have determined their position (perhaps using GPS) then you can keep them in synch relative to each other using PLL or similar - surely.

You still need a common reference though, even atomic clocks drift
relative to each other

Yes indeed - a master transmitter, to which all the others synchronise adjusting their timing for the propagation delay from the master. If the master drifts - they all drift together. So again WTF were they using GPS?

Name me another cheap and easy to receive timing reference signal, that
can received easily at all Tx sites from Jersey to The Shetland Islands ?

1. The DAB broadcast itself from the 'master' transmitter.
It might drift from atomic time, but so what.
2. Anthorn - see https://en.wikipedia.org/wiki/Time_from_NPL


For DAB the wavelength is short, but I remember driving through southern Scotland on the A7 many years ago and the beats between the English and Scottish radio 4 LW transmitters as I drove along.

Yes, and what's that got to do with it ?

This is the effect they are trying to defeat isn't it. If the stations are out of synch the signals will beat with each other.



--
Mark
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