Which pips?

On Tue, 10 Sep 2013 19:11:58 +0100, Phil Cook
wrote:

On 10/09/2013 18:41, Scott wrote:
On Mon, 09 Sep 2013 17:10:28 -0500, "Steve Thackery"
wrote:



To summarise: the FM pips. The DAB pips are delayed because your DAB
radio takes a certain time to decode the signal.

I understood the 'official' pips were on long wave and that FM was
delayed albeit nothing like as much as DAB.

Surely the propagation delays on FM would be the same as AM?

I believe the delay is in distribution to the network of FM
transmitters.

OP here - thanks chaps: a very interesting and informative discussion!

Of course, I don't _really_ need to know which pips are the more
accurate, I was just curious (given that we were brought up to believe
that the Pips are THE exact time). If I do ever need to know the
precise time (and which of us ever does?) then I have my Aldi weather
station, which tunes into one of them there atomic clocks.

Cheers
J.

Phil Cook wrote...

Surely the propagation delays on FM would be the same as AM?

FM is distributed via a NICAM digital system with resultant delays.

The Venerable Jim of this group has an excellent article on this at:
http://www.audiomisc.co.uk/BBC/PCMandNICAM/History.html

--
UnsteadyKen

Phil Cook wrote:
On 10/09/2013 18:41, Scott wrote:
On Mon, 09 Sep 2013 17:10:28 -0500, "Steve Thackery"
wrote:



To summarise: the FM pips. The DAB pips are delayed because your DAB
radio takes a certain time to decode the signal.

I understood the 'official' pips were on long wave and that FM was
delayed albeit nothing like as much as DAB.

Surely the propagation delays on FM would be the same as AM?
No, they're much shorter waves. Think about a sausage dog running.

Bill

On 10/09/2013 20:42, Bill Wright wrote:
Phil Cook wrote:
On 10/09/2013 18:41, Scott wrote:
On Mon, 09 Sep 2013 17:10:28 -0500, "Steve Thackery"
wrote:



To summarise: the FM pips. The DAB pips are delayed because your DAB
radio takes a certain time to decode the signal.

I understood the 'official' pips were on long wave and that FM was
delayed albeit nothing like as much as DAB.

Surely the propagation delays on FM would be the same as AM?

No, they're much shorter waves. Think about a sausage dog running.

They may be shorter waves but they come much more often so the speed
over the ground is the same, round about C if my physics doesn't fail me.

As pointed out elsewhere the delays over FM relative to AM were due to
the transmission to the transmitters.
--
Phil Cook

In article ,
Ian Jackson wrote:
However, the
delays on the audio feeds to all the other transmitters (LW and FM) will
vary (especially if carried on telephone lines, and less so on fibre),
so depending on their path lengths, the delays would vary quite a bit (a
few milliseconds?).

The distribution system is digital and will invariably introduce delay.
Maybe not much but easily measurable.

Droitwich at one time had a direct DC analogue line as a backup. Dunno if
it still has.

--
*Money isn't everything, but it sure keeps the kids in touch.

Dave Plowman London SW
To e-mail, change noise into sound.

On Tue, 10 Sep 2013 16:59:27 +0100, Ian Jackson
wrote:

In message , "Dave Plowman (News)"
writes
In article ,
Bill Wright wrote:
Yes - and different Digital radios take differing times to decode,
If you have 6 satellite receivers running on the same channel the audio
is very weird, just slightly different delays. Very odd if you move your
head about.

You get different delays from FreeView receivers too. But DAB has the
biggest delay I've noticed. Not bothered with satellite for the pips.

The old analogue Sky News seemed to be remarkably accurate with its
time. Their news studio clock seemed to be spot-on with the (analogue)
radio pips, and I think there should have been a delay of about half a
second. Possibly they set their clock half a second fast?

There can be no other explanation. You know what Scotty used to say
about the laws of physics.

--
Graham.

%Profound_observation%

On Mon, 09 Sep 2013 22:26:38 +0100, Another John
wrote:

I'm sure this has been asked many times before, but I haven't seen it
....

I had both my digital radio and my FM radio on this teatime, in
different rooms. At 6pm The Pips were broadcast. Given that digital is
always out of synch with FM -- which is the more accurate time signal?

The FM signal is the more accurate (somewhere in the region of 3 ms
or so propagation delay with perhaps a Nicam 3 processing delay of
several hundred microseconds on top of that).

The total propagation delay for DAB and DVB is in the region of a
couple of seconds give or take half a second and is mostly processing
delay. We haven't enjoyed Live TV broadcasting in the UK since the
last of the analogue transmitters were shut down.

What we get is "Near Live" broadcasting for the supposedly 'Live
programmes' that are now broadcast. That's simply the price we pay for
being able to squeeze some four to six TV channels into the space of a
single analogue TV channel and similarly for DAB.

Come to think of it I have another question, related, and equally dumb.
Given that digital is digital, and therefore completely under the
control of the broadcasters (as opposed to the 'organic' FM signal), why
in the name of all that's holy do "they" not synchronise the football
commentary over digital radio, so that it matches TV coverage of the
game? It's bloody annoying hearing about a goal several seconds before
(or sometimes after?) it happens!

I don't think there's a simple (i.e. cheap) way for the broadcasters
to implement such a laudible scheme. One major and obvious impediment
is down to the broadcasters involved no longer being in direct control
of the whole distribution chain and the transmitters themselves.

Another impediment is the variation in the design of the receiving
equipment purchased by the listening/viewing public. The variations in
the old analogue kit regarding propagation delays would have been a
trivial matter of microseconds rather than a not insignificant matter
of hundreds of milliseconds seen in modern receiving equipment.

In short, the broadcasters no longer have complete control as you
incorrectly surmised.

HTH & HAND
--
Regards, J B Good

Phil Cook wrote:
On 10/09/2013 20:42, Bill Wright wrote:
Phil Cook wrote:
On 10/09/2013 18:41, Scott wrote:
On Mon, 09 Sep 2013 17:10:28 -0500, "Steve Thackery"
wrote:



To summarise: the FM pips. The DAB pips are delayed because your DAB
radio takes a certain time to decode the signal.

I understood the 'official' pips were on long wave and that FM was
delayed albeit nothing like as much as DAB.

Surely the propagation delays on FM would be the same as AM?

No, they're much shorter waves. Think about a sausage dog running.

They may be shorter waves but they come much more often so the speed
over the ground is the same, round about C if my physics doesn't fail me.

It doesn't make any difference how often they come. Just because there
are a lot of sausage dogs arriving that doesn't mean they're coming any
faster. It's just that a lot are setting off so more arrive. Obviously
you need more Pedigree Chum.

And what's this 'C' of which you speak? I know that lower case c =
186282 sausage dogs per second, but I've never heard of 'C' (except I
was in the C stream for maths).

Bill

On 11/09/2013 03:51, Bill Wright wrote:
Phil Cook wrote:
On 10/09/2013 20:42, Bill Wright wrote:
Phil Cook wrote:
On 10/09/2013 18:41, Scott wrote:
On Mon, 09 Sep 2013 17:10:28 -0500, "Steve Thackery"
wrote:



To summarise: the FM pips. The DAB pips are delayed because your DAB
radio takes a certain time to decode the signal.

I understood the 'official' pips were on long wave and that FM was
delayed albeit nothing like as much as DAB.

Surely the propagation delays on FM would be the same as AM?

No, they're much shorter waves. Think about a sausage dog running.

They may be shorter waves but they come much more often so the speed
over the ground is the same, round about C if my physics doesn't fail me.

It doesn't make any difference how often they come. Just because there
are a lot of sausage dogs arriving that doesn't mean they're coming any
faster. It's just that a lot are setting off so more arrive. Obviously
you need more Pedigree Chum.

And what's this 'C' of which you speak? I know that lower case c =
186282 sausage dogs per second, but I've never heard of 'C' (except I
was in the C stream for maths).

Ah, I is an h, well at least some of the time. It should of course be
c, but how much does the air slow the sausage dogs down? Should we be
considering their wave or particle nature? Also what effect will that
cat have, or can't we tell?
--
Phil Cook