Level of the BBC's Pips ?

Post by Malcolm Stewart
I assume that the BBC time signal pips are at the same level on all
programmes. Can anyone tell me what it is relative to max modulation?
So far, I've found lots of references to VU / PPM meters etc. but it's not
clear to me how it relates to, say, full scale on the ADC converter on my
soundcard.
TIA

Slightly off-topic, but does the Beeb do anything to synchronise the
pips over different transmission paths (eg, transmit them a bit early on
DAB/DTT and earlier still on satellite)? Otherwise they will be a
second or more late.

Nick

Mark Carver

2005-02-24 13:21:58 UTC

Slightly off-topic, but does the Beeb do anything to synchronise the
pips over different transmission paths (eg, transmit them a bit early on
DAB/DTT and earlier still on satellite)?

No, they don't

Post by Nick
Otherwise they will be a second or more late.

Yes, they are !

(That's also AIUI why the 'station clocks' are no longer seen on any TV
channel before the News etc).

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

Nick

2005-02-24 13:30:00 UTC

Slightly off-topic, but does the Beeb do anything to synchronise the
pips over different transmission paths (eg, transmit them a bit early
on DAB/DTT and earlier still on satellite)?

No, they don't

Post by Nick
Otherwise they will be a second or more late.

Yes, they are !
(That's also AIUI why the 'station clocks' are no longer seen on any TV
channel before the News etc).

Except for the News24 countdown. Perhaps this is corrected a bit as it
is only available over digital paths so the encoding/decoding delay will
be constant even if the transmission delay varies.

Nick

Stephen Neal

2005-02-26 20:48:29 UTC

Post by Malcolm Stewart
I assume that the BBC time signal pips are at the same level on all
programmes. Can anyone tell me what it is relative to max
modulation? So far, I've found lots of references to VU / PPM
meters etc. but it's not
clear to me how it relates to, say, full scale on the ADC converter on my
soundcard.
TIA

Slightly off-topic, but does the Beeb do anything to synchronise the
pips over different transmission paths (eg, transmit them a bit
early on DAB/DTT and earlier still on satellite)?

No, they don't

Post by Nick
Otherwise they will be a second or more late.

Yes, they are !
(That's also AIUI why the 'station clocks' are no longer seen on any
TV channel before the News etc).

Except for the News24 countdown. Perhaps this is corrected a bit as
it is only available over digital paths so the encoding/decoding
delay will be constant even if the transmission delay varies.

Yep - though News 24 also goes out on BBC One at some times, and that will
have all sorts of differing delays depending upon the region and platform I
suspect. (And will include analogue...)

Steve

fsol

2005-02-26 14:33:07 UTC

Slightly off-topic, but does the Beeb do anything to synchronise the
pips over different transmission paths (eg, transmit them a bit early on
DAB/DTT and earlier still on satellite)?

No, they don't

Post by Nick
Otherwise they will be a second or more late.

Yes, they are !
(That's also AIUI why the 'station clocks' are no longer seen on any TV
channel before the News etc).

you maight wnat to try the following

sky channel 151
or analogue or DTT S4C

saturday @ 19:59:30 for Newyddion a Chwaraeon

or
sunday @ 19:14:30 for Newyddion

The news from the bbc, which when i last looked was preceeded by an
on-screen clock.
I'm not sure, but i suspect that there may be other news broadcasts
during the week, which may or may not be preceded by a clock . Have a
look and see.

!
fsol
!

Mark S

2005-02-24 18:38:04 UTC

Slightly off-topic, but does the Beeb do anything to synchronise the pips
over different transmission paths (eg, transmit them a bit early on
DAB/DTT and earlier still on satellite)? Otherwise they will be a second
or more late.

No. You'd end up with a logistical nightmare.

John Howells

2005-02-24 19:06:31 UTC

Slightly off-topic, but does the Beeb do anything to synchronise the pips
over different transmission paths (eg, transmit them a bit early on
DAB/DTT and earlier still on satellite)? Otherwise they will be a second
or more late.

No. You'd end up with a logistical nightmare.

Besides which it would not work, as not all decoders cause the same delay.
If I set three receivers to the same channel then:

A Pioneer outputs first.
A Nebula DigiTV outputs second.
A Twinhan VisionPlus outputs third.

In each case the delay is significant, by two or three words or more, much
more than just a slight echo, and the results are the same for both TV and
radio.

John Howells

Matti Lamprhey

2005-02-24 19:37:27 UTC

Post by John Howells

Post by Nick
Slightly off-topic, but does the Beeb do anything to synchronise
the pips over different transmission paths (eg, transmit them a
bit early on DAB/DTT and earlier still on satellite)? Otherwise
they will be a second or more late.

No. You'd end up with a logistical nightmare.

Besides which it would not work, as not all decoders cause the same
A Pioneer outputs first.
A Nebula DigiTV outputs second.
A Twinhan VisionPlus outputs third.
In each case the delay is significant, by two or three words or more,
much more than just a slight echo, and the results are the same for
both TV and radio.

BBC News 24 at 6pm this evening gave a countdown which synchronized with
my radio-controlled wallclock within 100ms. [Daewoo Setpal receiving
Mendip here in Newport.]

Matti

harrogate2

2005-02-24 18:42:38 UTC

Post by Malcolm Stewart
I assume that the BBC time signal pips are at the same level on all
programmes. Can anyone tell me what it is relative to max

modulation?

Post by Malcolm Stewart
So far, I've found lots of references to VU / PPM meters etc. but

it's

Post by Malcolm Stewart
not
clear to me how it relates to, say, full scale on the ADC

converter on my

Post by Malcolm Stewart
soundcard.
TIA

Slightly off-topic, but does the Beeb do anything to synchronise the pips
over different transmission paths (eg, transmit them a bit early on
DAB/DTT and earlier still on satellite)? Otherwise they will be a second
or more late.

No. You'd end up with a logistical nightmare.

Auntie usually says that these days the only 'accurate' pips for we
irks is 198KHz on Droitwich!

--
Woody

harrogate2 at ntlworld dot com

Mark Carver

2005-02-24 19:44:59 UTC

Post by harrogate2
Auntie usually says that these days the only 'accurate' pips for we
irks is 198KHz on Droitwich!

Ah but what distance from Droitwich must you be for complete accuracy ? :-)

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

Graham

2005-02-24 22:24:00 UTC

Post by Mark Carver
Ah but what distance from Droitwich must you be for complete accuracy ? :-)

Your question may have been rhetorical, nevertheless according to:
http://www.miketodd.net/other/gts.htm
the answer is about 100 miles.

"Even though the pips are generated to a very high degree of accuracy, the
transmitted signal takes a finite time to travel from Broadcasting House to
a transmitter, and then from the transmitter to the radio. Of course, the
further a radio is from the transmitter, the greater the delay - at 200
miles from the Radio 4 LW transmitter at Droitwich the delay is roughly a
thousandth of a second - and as a compromise the pips are delayed so that
they are accurate at a distance of about 100 miles from the transmitter."

The same website also gives an account of the now famous case of the
musician, who wrote a flute piece intended to be accompanied by the BBC TS.

He complained to the BBC that the normally 1000Hz pips were flat.

It turns out that (AFAIK) to this day the pitch of the pips are not locked
to a reference, or even crystal controlled but relies on a free running R-C
oscillator

--
Graham.

%Profound_observation%

Prometheus

2005-02-25 07:09:40 UTC

In article <***@individual.net>, Graham <***@privacy.net>
writes

Post by Graham

Post by Mark Carver
Ah but what distance from Droitwich must you be for complete accuracy ?

:-)
http://www.miketodd.net/other/gts.htm
the answer is about 100 miles.
"Even though the pips are generated to a very high degree of accuracy, the
transmitted signal takes a finite time to travel from Broadcasting House to
a transmitter, and then from the transmitter to the radio. Of course, the
further a radio is from the transmitter, the greater the delay - at 200
miles from the Radio 4 LW transmitter at Droitwich the delay is roughly a
thousandth of a second - and as a compromise the pips are delayed so that
they are accurate at a distance of about 100 miles from the transmitter."

This does not makes sense since if you "delay" them they will always be
late, they would have to be generated in advance of true time. Another
question is how far the user sits from their radio, the audio delay in
air is about a thousandth of a second for ever foot. Of course since the
pips are intended to be used by people manually setting clocks the human
uncertainty will be several tenths of a second so the propagation delay
is insignificant. If you really need precise time use either GPS or an
MSF that allows for propagation delay.

--
Ian G8ILZ

Mark Carver

2005-02-25 16:40:27 UTC

Post by Graham

Post by Mark Carver
Ah but what distance from Droitwich must you be for complete accuracy ?

:-)
http://www.miketodd.net/other/gts.htm
the answer is about 100 miles.

Thanks for the link.

100 miles from Droitwich, now what big city would that be ? :-)

[snip]

So for complete accuracy I need to be tuned to LW, 100 miles from
Droitwich, and with my ear drum in contact with the radio's speaker cone.

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

JPG

2005-02-25 22:32:54 UTC

On Fri, 25 Feb 2005 16:40:27 +0000, Mark Carver

Post by Graham

Post by Mark Carver
Ah but what distance from Droitwich must you be for complete accuracy ?

:-)
http://www.miketodd.net/other/gts.htm
the answer is about 100 miles.

Thanks for the link.
100 miles from Droitwich, now what big city would that be ? :-)
[snip]
So for complete accuracy I need to be tuned to LW, 100 miles from
Droitwich, and with my ear drum in contact with the radio's speaker cone.

All the stray capacitance in the transistors will add a delay from the
aerial to the loadspeaker, so really you need a crystal set, whereby
the electronics is removed completely. Even then there is more than a
nanosecond's delay for each foot of wiring.

BTW, Maplins had a radio-controlled digital clock for £9.99 in their
sale recently.

JPG

Owain

2005-02-26 15:03:17 UTC

"JPG" wrote
| BTW, Maplins had a radio-controlled digital clock for £9.99
| in their sale recently.

Lidl had one for £2.99 this week. Including battery.

Owain

Roger Wilmut

2005-02-26 15:47:39 UTC

Post by harrogate2
Auntie usually says that these days the only 'accurate' pips for we
irks is 198KHz on Droitwich!

Ah but what distance from Droitwich must you be for complete accuracy ? :-)

In the 1960s we in the External Services Control Room were told the
pips were used for navigation at sea. If we mucked one up (they were
inserted manually) by, for example, missing a pip, we were threatened
with the spectre of ships running aground all over the world. (One of
my colleagues missed two pips - the middle two. He took the key off
after two, said "Oh, Christ", and put it on again in time for the last
two. It was such a stupid thing to do that all his boss said was "Be
more careful next time.") If an entire time signal was missed it had to
be broadcast on the next quarter-hour instead - even if it was right
across programme.

Nowadays nobody navigates like that, of course (I wonder if they really
did then?).

M. J. Powell

2005-02-26 20:18:18 UTC

In message <260220051547397567%***@nospam.yahoo.com>, Roger Wilmut
<***@nospam.yahoo.com> writes

snip

Post by Roger Wilmut
In the 1960s we in the External Services Control Room were told the
pips were used for navigation at sea. If we mucked one up (they were
inserted manually) by, for example, missing a pip, we were threatened
with the spectre of ships running aground all over the world. (One of
my colleagues missed two pips - the middle two. He took the key off
after two, said "Oh, Christ", and put it on again in time for the last
two. It was such a stupid thing to do that all his boss said was "Be
more careful next time.") If an entire time signal was missed it had to
be broadcast on the next quarter-hour instead - even if it was right
across programme.
Nowadays nobody navigates like that, of course (I wonder if they really
did then?).

It would be only for checking the ship's chronometers.

Mike

--
M.J.Powell

Prometheus

2005-02-27 07:51:44 UTC

Post by M. J. Powell
snip

It would be only for checking the ship's chronometers.

Which is important since time is required to provide the longitude
component of location. If your ship's chronometer does not keep good
time, or you reset it to inaccurate time pips then you could run aground
on am umbuoyed, charted submerged sand bank.

--
Ian G8ILZ

m***@privacy.net

2005-02-24 12:55:19 UTC

On 24 Feb,

They alway used to be PPM4, but they could be anything these days after the
processing.

--
BD
change lycos to yahoo to reply

Nigel M

2005-02-24 16:26:47 UTC

Post by m***@privacy.net

Post by Malcolm Stewart
I assume that the BBC time signal pips are at the same level on all
programmes. Can anyone tell me what it is relative to max modulation?

They alway used to be PPM4

Which is 8dB below maximum peak, 6dB below "normal" peak.

--
Nigel M
"Occam's razor is not always sharp"

m***@privacy.net

2005-02-25 00:32:23 UTC

On 24 Feb,

Post by Nigel M

Post by m***@privacy.net

Post by Malcolm Stewart
I assume that the BBC time signal pips are at the same level on all
programmes. Can anyone tell me what it is relative to max modulation?

They alway used to be PPM4

Which is 8dB below maximum peak, 6dB below "normal" peak.

depends on which 'maximum' peak, or which 'normal' peak. Correct for AM
radio. VHF/FM and TV sound has had several different ones, particularly with
stereo, and headroom on digital formats is generally higher.

--
BD
change lycos to yahoo to reply

Marcus

2005-02-24 13:41:07 UTC

WTF

--
Marcus

I like people, they are bio-degradable !.

Roger Wilmut

2005-02-24 17:12:07 UTC

The pips are supposed to be at 4 on the PPM: this is 8dB below peak
level (6 on the PPM). Line-up tone is at the same level. VU meters will
tend to show tone as reading 4db below maximum because of the
adjustment for not showing transient peaks properly. 8dB below peak
equates to 0.398 times the peak voltage (so if the peak voltage was 1v,
-8dB would be 398 millivolts).

(Nation shall peak six unto nation.)

Malcolm Stewart

2005-02-24 18:53:48 UTC

Post by Roger Wilmut
The pips are supposed to be at 4 on the PPM: this is 8dB below peak
level (6 on the PPM). Line-up tone is at the same level. VU meters will
tend to show tone as reading 4db below maximum because of the
adjustment for not showing transient peaks properly. 8dB below peak
equates to 0.398 times the peak voltage (so if the peak voltage was 1v,
-8dB would be 398 millivolts).
(Nation shall peak six unto nation.)

Thanks for all the replies.
I've now done some further trawling, and found a technical spec from the BBC
for contractors offering digitally recorded programme material. On p3, this
.pdf file (long url below - will need latter part copying and pasting)
suggests that PPM4 is 18dB down on max level, and that PPM6 is 10dB down on
max level.

www.bbc.co.uk/scotland/aboutus/commissioning/
documents/radio_s_tech_requirements.pdf

So I seem to have found a spec. for contractors supplying stuff on CD, but
whether that's the same as what gets transmitted is still a mystery! My own
measurements suggest that the pips level is around -14dB wrt peak.
Puzzled...

--
M Stewart
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm

jim

2005-02-24 18:20:11 UTC