Re: Amusing interview with DRDB boss

"hwh" <iimeeltje@xxxxxxxxxxxxxxxxxx> wrote in message
news:49e747f0$0$194$e4fe514c@xxxxxxxxxxxxxx
BBC is biased towards DAB wrote:
"hwh" <iimeeltje@xxxxxxxxxxxxxxxxxx> wrote in message
news:49e4a14b$0$184$e4fe514c@xxxxxxxxxxxxxx
BBC is biased towards DAB wrote:
That's 8, 10 and 10 lots of expensive shit per multiplex,
respectively, including a highly accurate clock per transmitter
They solve that by using a GPS receiver.


Could you explain how that works?

Each GPS satellite transmits data that indicates its location and
the
current time. All GPS satellites synchronize operations so that
these
repeating signals are transmitted at the same instant. The signals,
moving at the speed of light, arrive at a GPS receiver at slightly
different times because some satellites are farther away than
others.
The distance to the GPS satellites can be determined by estimating
the
amount of time it takes for their signals to reach the receiver.
When
the receiver estimates the distance to at least four GPS satellites,
it
can calculate its position in three dimensions.
(http://www.nasm.si.edu/gps/work.html)

One of the fringe benefits is that a GPS receiver can be used as a
very
accurate clock. When used in a network, this can be used to
synchronize
the transmissions from various sites. It can also be used to
transmit a
certain station with an 'offset' to compensate for instance if the
station is a bit too far away from other stations.

This synchronization is achieved by telling all transmitters at
regular
intervals when a certain bit of data should be transmitted. This is
one
of the causes of the delay often experienced in DAB compared to
analog
transmissions, as a certain safety margin is build in to the system,
to
allow the signals to arrive at all transmitter sites in time for
transmission.

Many computer networks also use GPS as a source for a timing server.
This in turn synchronizes the clocks of all computers checking the
time
of this timing server. In fact this has replaced the use of long
wave
receivers for timing transmitters in many cases.


Thanks for the explanation.




--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

"It is the sheer volume of online audio content available via
internet-connected devices which terrifies the UK radio industry. I
believe that broadband-delivered radio will explode in the years to
come, offering very local, unregulated content, as well as opening a
window to the radio stations of the world." - from the Myers Report


.

Relevant Pages

  • Re: Amusing interview with DRDB boss
    ... Each GPS satellite transmits data that indicates its location and the current time. ... The signals, moving at the speed of light, arrive at a GPS receiver at slightly different times because some satellites are farther away than others. ... The distance to the GPS satellites can be determined by estimating the amount of time it takes for their signals to reach the receiver. ... This is one of the causes of the delay often experienced in DAB compared to analog transmissions, as a certain safety margin is build in to the system, to allow the signals to arrive at all transmitter sites in time for transmission. ...
    (alt.radio.digital)
  • Re: Lightsquared/GPS [telecom]
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  • Re: Only 2 satellites necessary?
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  • Re: Track someone elses GPS?
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  • Re: Only 2 satellites necessary?
    ... > Sam Wormley wrote: ... >>Given knowledge of elevation and time, a GPS receiver should be ... >>able to determine position accurately from two GPS satellites. ...
    (sci.geo.satellite-nav)