In article ,
charles wrote:
It certainly did it with halogen lamps.

How did they manage to lock the mains to the TV pulse generator, then?

Don't be sill, I'm taking about a 10Hz beat.

Do you mean by that the mains would have to be 10Hz away from 50? I've
seen 2 or 3 adrift on my meter here - but never that much.

But even then I'd be surprised if a tungsten filament lamp reacted at all.
Things like some fluorescents and discharge lamps are a different matter
if running at mains frequency. Which is why all the general purpose studio
luminairs were all tungsten.

--
*Half the people in the world are below average.

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

In article ,
charles wrote:
In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
The studio lighting, unless dc driven, neads to have the same
frequency (to a first order) as the tv system. A serious 10Hz beat
can happen if not.

Must make location shooting with battery cameras impossible. ;-)

It shows taht you were only ever involved with sound.

But closely involved with actual shooting. My guess is you weren't?

When TV came off mains lock, it would have then been kept to an extremely
accurate 50 Hz (or whatever). Mains can vary quite some way either side.
Are you saying the mains feed to the lights at TC etc was in someway
better in this respect?

--
*And the cardiologist' s diet: - If it tastes good spit it out.

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

In article ,
John Williamson wrote:
How did they manage to lock the mains to the TV pulse generator, then?

Don't be sill, I'm taking about a 10Hz beat.

Which you won't get unless you're using 60Hz frame rate with 50Hz lights
or vice versa.

I'm not convinced that would be a problem with tungsten lighting anyway.
Large filament tungsten takes ages to react to any change in voltage. If
it reacted to an AC sine wave by switching on and off lots of humans would
see it - as happens with fast reacting lights like some type of
fluorescents.

--
*A fool and his money are soon partying *

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

In article ,
charles wrote:
Which you won't get unless you're using 60Hz frame rate with 50Hz
lights or vice versa.

Which is what was the original point under discussion.

No it wasn't.

--
*It IS as bad as you think, and they ARE out to get you.

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

On 18/04/14 16:11, Tim Streater wrote:
In article , Uncle Peter wrote:

On Fri, 18 Apr 2014 12:30:03 +0100, The Natural Philosopher
wrote:

Or if there is a tube strike, the underground can sell its surplus at
whatever price it can get.

The underground has its own power station?

I think it's always had one, at least since it was electrified. I
remember reading about it in the same book that had the article about
the Norwich Heat Pump.


Nah. what I meant was that if it has contracted to take electricity it
cannot use, it can sell that on.


I don't think the underground has its own power stations at all.
Substations, yes. Got to turn into into DC somehow.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Fri, 18 Apr 2014 15:19:09 +0100, The Natural Philosopher wrote:

On 18/04/14 16:11, Tim Streater wrote:
In article , Uncle Peter wrote:

On Fri, 18 Apr 2014 12:30:03 +0100, The Natural Philosopher
wrote:

Or if there is a tube strike, the underground can sell its surplus at
whatever price it can get.

The underground has its own power station?

I think it's always had one, at least since it was electrified. I
remember reading about it in the same book that had the article about
the Norwich Heat Pump.


Nah. what I meant was that if it has contracted to take electricity it
cannot use, it can sell that on.


I don't think the underground has its own power stations at all.
Substations, yes. Got to turn into into DC somehow.

I would have thought they'd just sell it back to where they got it from. Perhaps the contract might say we will restock it for you at 20% fee.

--
If the Internet is a superhighway, then AOL must be a fleet of farm equipment that straddles five lanes and pays no heed to "Keep Right Except to Pass" signs.

In message , "Dave Plowman (News)"
writes
In article ,
charles wrote:
In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
The studio lighting, unless dc driven, neads to have the same
frequency (to a first order) as the tv system. A serious 10Hz beat
can happen if not.

Must make location shooting with battery cameras impossible. ;-)

It shows taht you were only ever involved with sound.

But closely involved with actual shooting. My guess is you weren't?

When TV came off mains lock, it would have then been kept to an extremely
accurate 50 Hz (or whatever). Mains can vary quite some way either side.


Not by a lot, take a look at this item.

http://www.dynamicdemand.co.uk/grid.htm#


--
Bill

On Fri, 18 Apr 2014 14:32:59 +0100, The Natural Philosopher
wrote:

On 18/04/14 14:02, Andrew Gabriel wrote:
In article ,
John Rumm writes:
I don't think its appropriate to call this two phase - split phase
perhaps. Its basically a single phase supply transformer with a centre
tap used as the neutral, giving a 110 - 0 - 110 supply.

Whether it's called 2-phase or not is a never ending argument in
US forums.

Its single phase really or two 180 degree out of phases.

Less confusingly referred to as bi-phase.


In physics/maths terms, it's clearly valid to call it
two phases, but in supply distribution jargon, they have a 2-phase
supply which is something completely different (refers to a 4-wire
circuit with 90 degrees between 2-phases).

I doubt it.

no one uses 90 degree phase differences.

True when it comes to distribution networks. It' only generated
locally to the motors that use an approximation to 90 degree phases.


120 degrees as 3 phase is used for all transmission.

A fully balanced 3 phase supply only needs 50% more copper to triple
the power delivery capacity of the cabling. Adding a neutral only
doubles the copper costs for that 3 fold boost in line capacity. The
neutral never has to carry more than any single phase current in the
worst case imbalance (a loss of 1 or 2 of the 3 phases).

Polyphase using more than 3 phases aren't used because the copper
savings return versus complexity rapidly diminish beyond the savings
made with a 3 phase system.
--
Regards, J B Good

On Fri, 18 Apr 2014 14:54:51 +0100, "Dave Plowman (News)"
wrote:

In article ,
John Williamson wrote:
How did they manage to lock the mains to the TV pulse generator, then?

Don't be sill, I'm taking about a 10Hz beat.

Which you won't get unless you're using 60Hz frame rate with 50Hz lights
or vice versa.

I'm not convinced that would be a problem with tungsten lighting anyway.
Large filament tungsten takes ages to react to any change in voltage. If
it reacted to an AC sine wave by switching on and off lots of humans would
see it - as happens with fast reacting lights like some type of
fluorescents.

Tungsten filament lamps generate a 100Hz component which can't be
detected by normal human vision, not even peripherally where the eye
is most sensitive to flicker. The only reason for fluorescent tube
flicker to become detectable is when the tube starts to partially
rectify the 50Hz ac waveform (only a 3% imbalance is required for this
to become noticable).

The camera strobe effect with tungsten lighting is only a slight
problem because of the very shallow modulation depth of the 100Hz
flicker effect whereas, in the case of discharge tubes such as a
fluorescent lamp, the depth of modulation is 100%, only mitigated by
the decay emmission light curve of the phosphor coating.

The worse lamp types for this undesired strobing effect are the high
pressure mercury vapour and xenon gas discharge lamps, not forgetting
the sodium street lighting lamps, since these don't employ a phosphor
coating which would otherwise 'smooth out' the flicker.
--
Regards, J B Good

In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
It certainly did it with halogen lamps.

How did they manage to lock the mains to the TV pulse generator, then?

Don't be sill, I'm taking about a 10Hz beat.

Do you mean by that the mains would have to be 10Hz away from 50? I've
seen 2 or 3 adrift on my meter here - but never that much.

If yiou are crating programmes using NTSC 525/60 in the UK, then the maisn
is 10Hz away from field frequency.



But even then I'd be surprised if a tungsten filament lamp reacted at all.
Things like some fluorescents and discharge lamps are a different matter
if running at mains frequency. Which is why all the general purpose studio
luminairs were all tungsten.

yet a 10Hz beat was visible.

--
From KT24

Using a RISC OS computer running v5.18

In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
The studio lighting, unless dc driven, neads to have the same
frequency (to a first order) as the tv system. A serious 10Hz beat
can happen if not.

Must make location shooting with battery cameras impossible. ;-)

It shows taht you were only ever involved with sound.

But closely involved with actual shooting. My guess is you weren't?

When TV came off mains lock, it would have then been kept to an extremely
accurate 50 Hz (or whatever). Mains can vary quite some way either side.
Are you saying the mains feed to the lights at TC etc was in someway
better in this respect?


No. TC had a 60Hz generator, but it only fed electronics, not lighting.

--
From KT24

Using a RISC OS computer running v5.18

On Fri, 18 Apr 2014 16:40:49 +0100, Tim Streater wrote:

In article , The Natural Philosopher
wrote:

On 18/04/14 16:11, Tim Streater wrote:
In article , Uncle Peter wrote:

On Fri, 18 Apr 2014 12:30:03 +0100, The Natural Philosopher
wrote:

Or if there is a tube strike, the underground can sell its surplus at
whatever price it can get.

The underground has its own power station?

I think it's always had one, at least since it was electrified. I
remember reading about it in the same book that had the article about
the Norwich Heat Pump.

Nah. what I meant was that if it has contracted to take electricity it
cannot use, it can sell that on.

I don't think the underground has its own power stations at all.
Substations, yes. Got to turn into into DC somehow.

Not now, but see:

https://en.wikipedia.org/wiki/Lots_Road_Power_Station

which is what I was referring to.

I take it at that time they couldn't just contact the national grid and say we need 50MW.

--
Worlds most powerful nob enlarger - a space suit with a fly zip

In article ,
charles wrote:
Do you mean by that the mains would have to be 10Hz away from 50? I've
seen 2 or 3 adrift on my meter here - but never that much.

If yiou are crating programmes using NTSC 525/60 in the UK, then the
maisn is 10Hz away from field frequency.

Right. Well, despite working in TV all my life, the number of times I saw
this done was near zero. More usual to standards convert it later.


But even then I'd be surprised if a tungsten filament lamp reacted at
all. Things like some fluorescents and discharge lamps are a different
matter if running at mains frequency. Which is why all the general
purpose studio luminairs were all tungsten.

yet a 10Hz beat was visible.

You'll have to be more specific. What lamps were in use? Which studio?

--
*When the going gets tough, use duct tape

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

In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
Do you mean by that the mains would have to be 10Hz away from 50? I've
seen 2 or 3 adrift on my meter here - but never that much.

If yiou are crating programmes using NTSC 525/60 in the UK, then the
maisn is 10Hz away from field frequency.

Right. Well, despite working in TV all my life, the number of times I saw
this done was near zero. More usual to standards convert it later.


But even then I'd be surprised if a tungsten filament lamp reacted at
all. Things like some fluorescents and discharge lamps are a different
matter if running at mains frequency. Which is why all the general
purpose studio luminairs were all tungsten.

yet a 10Hz beat was visible.

You'll have to be more specific. What lamps were in use? Which studio?

TC6 & 7 were equipped for NTSC 525/60 as well as PAL 625/50 when they were
first equipped for colour, or perhaps I should say color. This facility
was only used once and, as you not, standards converters were used there
after. What lanterns? The same as in use in all the other colour studios
at the time. The dual purpose (fresnel/flood) - a BBC spec, but I can't
remebember who made them.

--
From KT24

Using a RISC OS computer running v5.18

On 18/04/2014 14:54, Dave Plowman (News) wrote:
In article ,
John Williamson wrote:
How did they manage to lock the mains to the TV pulse generator, then?

Don't be sill, I'm taking about a 10Hz beat.

Which you won't get unless you're using 60Hz frame rate with 50Hz lights
or vice versa.

I'm not convinced that would be a problem with tungsten lighting anyway.
Large filament tungsten takes ages to react to any change in voltage. If
it reacted to an AC sine wave by switching on and off lots of humans would
see it - as happens with fast reacting lights like some type of
fluorescents.

I'm not so sure about that. I've worked on film sets where the
generators were switchable to 48, 50 or 60Hz.

I can't see even the advertising guys bothering with that unless it made
a difference. Then again, I've seen a lot of discharge lamps on film sets.
--
Tciao for Now!

John.

On 18/04/2014 13:39, Uncle Peter wrote:
On Fri, 18 Apr 2014 10:32:34 +0100, charles
wrote:

In article ,
Vir Campestris wrote:
On 16/04/2014 19:17, Uncle Peter wrote:

But the frequency we choose will have an effect on the number of
frames
a second on TV, the speed of motors, etc, etc. And those things we
like
to be metric.

This is obviously why NTSC TV uses 29.97 frames per second.


It was 29.94 in my day. Inflation affects everything.

AFAIK the Hz ain't that accurate, it fluctuates. But the electric board
are supposed to maintain a precise average for things like clocks that
are based on it (although I don't think anything is nowadays).

The sync for analogue TV signals is derived from a crystal, so should be
accurate to within at worst one part per million. The crystal frequency
in the UK for PAL is specified as 4,433,618.75 Hz.


--
Tciao for Now!

John.

On Fri, 18 Apr 2014 19:15:27 +0100, Tim Streater wrote:

In article , Uncle Peter wrote:

On Fri, 18 Apr 2014 16:40:49 +0100, Tim Streater
wrote:

In article , The Natural Philosopher
wrote:

On 18/04/14 16:11, Tim Streater wrote:
In article , Uncle Peter wrote:

On Fri, 18 Apr 2014 12:30:03 +0100, The Natural Philosopher
wrote:

Or if there is a tube strike, the underground can sell its surplus at
whatever price it can get.

The underground has its own power station?

I think it's always had one, at least since it was electrified. I
remember reading about it in the same book that had the article about
the Norwich Heat Pump.

Nah. what I meant was that if it has contracted to take electricity it
cannot use, it can sell that on.

I don't think the underground has its own power stations at all.
Substations, yes. Got to turn into into DC somehow.

Not now, but see:

https://en.wikipedia.org/wiki/Lots_Road_Power_Station

which is what I was referring to.

I take it at that time they couldn't just contact the national grid
and say we need 50MW.

Presumably at the time there *was* no national grid.

I wasn't sure when we got it.

--
Waiter, waiter, what's wrong with these eggs?
I don't know Sir, I only laid the table.

On Fri, 18 Apr 2014 19:20:16 +0100, John Williamson wrote:

On 18/04/2014 13:39, Uncle Peter wrote:
On Fri, 18 Apr 2014 10:32:34 +0100, charles
wrote:

In article ,
Vir Campestris wrote:
On 16/04/2014 19:17, Uncle Peter wrote:

But the frequency we choose will have an effect on the number of
frames
a second on TV, the speed of motors, etc, etc. And those things we
like
to be metric.

This is obviously why NTSC TV uses 29.97 frames per second.


It was 29.94 in my day. Inflation affects everything.

AFAIK the Hz ain't that accurate, it fluctuates. But the electric board
are supposed to maintain a precise average for things like clocks that
are based on it (although I don't think anything is nowadays).

The sync for analogue TV signals is derived from a crystal, so should be
accurate to within at worst one part per million. The crystal frequency
in the UK for PAL is specified as 4,433,618.75 Hz.

Now that's what I call accurate.

--
"With god all things are possible" - yes: war, famine, pestilence, suffering, ..... -- Dave Moorman 2013

On Fri, 18 Apr 2014 15:40:49 +0000, Tim Streater
wrote:

In article , The Natural Philosopher
wrote:

On 18/04/14 16:11, Tim Streater wrote:
In article , Uncle Peter wrote:

On Fri, 18 Apr 2014 12:30:03 +0100, The Natural Philosopher
wrote:

Or if there is a tube strike, the underground can sell its surplus at
whatever price it can get.

The underground has its own power station?

I think it's always had one, at least since it was electrified. I
remember reading about it in the same book that had the article about
the Norwich Heat Pump.

Nah. what I meant was that if it has contracted to take electricity it
cannot use, it can sell that on.

I don't think the underground has its own power stations at all.
Substations, yes. Got to turn into into DC somehow.

Not now, but see:

https://en.wikipedia.org/wiki/Lots_Road_Power_Station

which is what I was referring to.

London Underground still have a power station at Greenwich.
It is just used as a standby now though in times past it was a
conventional power station,Gas turbines once installed were used in
the morning and evening peaks as they could be brought online quickly
.. It's these that are retained to be brought into operation quickly if
a power failure from the grid means that trains come to a stop in.
tunnels . Such an evacuation has to be controlled as it hasn't the
capacity to supply enough power to keep a full service running.
It might yet be used in another role.
Some details here.
http://www.energyforlondon.org/green...on-for-london/

G.Harman

In article ,
charles wrote:
You'll have to be more specific. What lamps were in use? Which studio?

TC6 & 7 were equipped for NTSC 525/60 as well as PAL 625/50 when they
were first equipped for colour, or perhaps I should say color. This
facility was only used once and, as you not, standards converters were
used there after. What lanterns? The same as in use in all the other
colour studios at the time. The dual purpose (fresnel/flood) - a BBC
spec, but I can't remebember who made them.

Right. And you're saying the studios couldn't be run at 525/60 because of
strobing from the lights?

--
*I have never hated a man enough to give his diamonds back.

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

In article ,
John Williamson wrote:
I'm not convinced that would be a problem with tungsten lighting
anyway. Large filament tungsten takes ages to react to any change in
voltage. If it reacted to an AC sine wave by switching on and off lots
of humans would see it - as happens with fast reacting lights like
some type of fluorescents.

I'm not so sure about that. I've worked on film sets where the
generators were switchable to 48, 50 or 60Hz.

I can't see even the advertising guys bothering with that unless it made
a difference. Then again, I've seen a lot of discharge lamps on film
sets.

I'm not well up on the types of lighting used on real film.

BBC studios at the time in question were virtually pure tungsten. Only
common discharge type was the CSI follow spot.

--
*Verbs HAS to agree with their subjects *

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

In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
You'll have to be more specific. What lamps were in use? Which studio?

TC6 & 7 were equipped for NTSC 525/60 as well as PAL 625/50 when they
were first equipped for colour, or perhaps I should say color. This
facility was only used once and, as you not, standards converters were
used there after. What lanterns? The same as in use in all the other
colour studios at the time. The dual purpose (fresnel/flood) - a BBC
spec, but I can't remebember who made them.

Right. And you're saying the studios couldn't be run at 525/60 because of
strobing from the lights?


Strobing ? a 10Hz flicker yes.

--
From KT24

Using a RISC OS computer running v5.18

In article ,
charles wrote:
In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
You'll have to be more specific. What lamps were in use? Which
studio?

TC6 & 7 were equipped for NTSC 525/60 as well as PAL 625/50 when
they were first equipped for colour, or perhaps I should say color.
This facility was only used once and, as you not, standards
converters were used there after. What lanterns? The same as in use
in all the other colour studios at the time. The dual purpose
(fresnel/flood) - a BBC spec, but I can't remebember who made them.

Right. And you're saying the studios couldn't be run at 525/60 because
of strobing from the lights?


Strobing ? a 10Hz flicker yes.

So why don't they flicker when the studio is running at 625/50 - since
it's not locked to the mains frequency? The eye would see a flicker at
much lower speeds than 10 a second.

--
*Toilet stolen from police station. Cops have nothing to go on.

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

In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
In article ,
Dave Plowman (News) wrote:
In article ,
charles wrote:
You'll have to be more specific. What lamps were in use? Which
studio?

TC6 & 7 were equipped for NTSC 525/60 as well as PAL 625/50 when
they were first equipped for colour, or perhaps I should say color.
This facility was only used once and, as you not, standards
converters were used there after. What lanterns? The same as in use
in all the other colour studios at the time. The dual purpose
(fresnel/flood) - a BBC spec, but I can't remebember who made them.

Right. And you're saying the studios couldn't be run at 525/60 because
of strobing from the lights?


Strobing ? a 10Hz flicker yes.

So why don't they flicker when the studio is running at 625/50 - since
it's not locked to the mains frequency? The eye would see a flicker at
much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than 0.1Hz?

--
From KT24

Using a RISC OS computer running v5.18

In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 - since
it's not locked to the mains frequency? The eye would see a flicker at
much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than 0.1Hz?

It's one of these things which seem to vary from person to person. Many
complain about flicker from some 50 Hz fluorescent lights saying it gives
them a headache. I can't say I've ever noticed it.

--
*I tried to catch some fog, but I mist.*

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

On Sat, 19 Apr 2014 13:26:31 +0100
"Dave Plowman (News)" wrote:

In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 -
since it's not locked to the mains frequency? The eye would see a
flicker at much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than
0.1Hz?

It's one of these things which seem to vary from person to person.
Many complain about flicker from some 50 Hz fluorescent lights saying
it gives them a headache. I can't say I've ever noticed it.


My wife complained about them even in the US, whereas they have never
bothered me anywhere. Except in China, where the hotel lights, all of
them, flickered at about 1.5 Hz.

--
Davey.

In article ,
Davey wrote:
It's one of these things which seem to vary from person to person.
Many complain about flicker from some 50 Hz fluorescent lights saying
it gives them a headache. I can't say I've ever noticed it.


My wife complained about them even in the US, whereas they have never
bothered me anywhere. Except in China, where the hotel lights, all of
them, flickered at about 1.5 Hz.

It also depends to some extend on the persistence of the phosphors used in
the tubes - with basic white being worse than decent ones in this respect.

--
*For every action, there is an equal and opposite criticism *

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

In article ,
Davey writes:
On Sat, 19 Apr 2014 13:26:31 +0100
"Dave Plowman (News)" wrote:

In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 -
since it's not locked to the mains frequency? The eye would see a
flicker at much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than
0.1Hz?

It's one of these things which seem to vary from person to person.
Many complain about flicker from some 50 Hz fluorescent lights saying
it gives them a headache. I can't say I've ever noticed it.


My wife complained about them even in the US, whereas they have never
bothered me anywhere. Except in China, where the hotel lights, all of
them, flickered at about 1.5 Hz.

No one can see 100Hz flicker - the limit is below 75Hz.
Animals with smaller brains can see higher frequencies,
and flies can see 1000Hz flicker.

With discharge tubes, a problem can be that they are partially
rectifying, resulting in 50Hz (or 60Hz) flicker, and most people
can see that. High intensity discharge lighting in shops was
often run on DC, to prevent this (prior to electronic ballasts).
There's a DC switching unit which alternates the DC flow every
switch-on, so you still get most of the expected lamp life.
This doesn't work with fluorescent tubes, because the mercury
tends to migrate to one end after some hours, leaving the other
end of the tube glowing only a very dim pink (argon gas).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 18/04/2014 13:39, Uncle Peter wrote:
On Fri, 18 Apr 2014 10:32:34 +0100, charles
wrote:

In article ,
Vir Campestris wrote:
On 16/04/2014 19:17, Uncle Peter wrote:

But the frequency we choose will have an effect on the number of
frames
a second on TV, the speed of motors, etc, etc. And those things we
like
to be metric.

This is obviously why NTSC TV uses 29.97 frames per second.


It was 29.94 in my day. Inflation affects everything.

AFAIK the Hz ain't that accurate, it fluctuates. But the electric board
are supposed to maintain a precise average for things like clocks that
are based on it (although I don't think anything is nowadays).

NTSC is that accurate. It's the mains that isn't.

And, yes, the mains is accurate over 24 hours.

Andy

On Sat, 19 Apr 2014 20:38:37 +0100, Vir Campestris wrote:

On 18/04/2014 13:39, Uncle Peter wrote:
On Fri, 18 Apr 2014 10:32:34 +0100, charles
wrote:

In article ,
Vir Campestris wrote:
On 16/04/2014 19:17, Uncle Peter wrote:

But the frequency we choose will have an effect on the number of
frames
a second on TV, the speed of motors, etc, etc. And those things we
like
to be metric.

This is obviously why NTSC TV uses 29.97 frames per second.


It was 29.94 in my day. Inflation affects everything.

AFAIK the Hz ain't that accurate, it fluctuates. But the electric board
are supposed to maintain a precise average for things like clocks that
are based on it (although I don't think anything is nowadays).

NTSC is that accurate. It's the mains that isn't.

And, yes, the mains is accurate over 24 hours.

So how did TVs work properly when they used the mains as a guide to frequency?

--
One of the first things you learn on your honeymoon is,
when you're carrying your bride over the threshold, always go in sideways,
unless of course two broken ankles and a concussion turn you on.

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

--
Tciao for Now!

John.

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

Andy

On 19/04/2014 13:26, Dave Plowman (News) wrote:
In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 - since
it's not locked to the mains frequency? The eye would see a flicker at
much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than 0.1Hz?

It's one of these things which seem to vary from person to person. Many
complain about flicker from some 50 Hz fluorescent lights saying it gives
them a headache. I can't say I've ever noticed it.

Much depends on the circumstance I find. 50Hz lights don't seem to
bother me particularly, but CRT flicker at anything less than about 82Hz
really bugs me. (as do modern electronic cats eyes, and some brake
lights, and many LED displays etc).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 19/04/2014 19:06, Andrew Gabriel wrote:
In article ,
Davey writes:
On Sat, 19 Apr 2014 13:26:31 +0100
"Dave Plowman (News)" wrote:

In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 -
since it's not locked to the mains frequency? The eye would see a
flicker at much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than
0.1Hz?

It's one of these things which seem to vary from person to person.
Many complain about flicker from some 50 Hz fluorescent lights saying
it gives them a headache. I can't say I've ever noticed it.


My wife complained about them even in the US, whereas they have never
bothered me anywhere. Except in China, where the hotel lights, all of
them, flickered at about 1.5 Hz.

No one can see 100Hz flicker - the limit is below 75Hz.

I found with large CRT screens that 75Hz vertical was not quite enough.
82Hz was where I stop noticing it.

Animals with smaller brains can see higher frequencies,
and flies can see 1000Hz flicker.

With discharge tubes, a problem can be that they are partially
rectifying, resulting in 50Hz (or 60Hz) flicker, and most people
can see that. High intensity discharge lighting in shops was
often run on DC, to prevent this (prior to electronic ballasts).
There's a DC switching unit which alternates the DC flow every
switch-on, so you still get most of the expected lamp life.
This doesn't work with fluorescent tubes, because the mercury
tends to migrate to one end after some hours, leaving the other
end of the tube glowing only a very dim pink (argon gas).

as seen in many buses and tube trains...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal hold. Is this anything to do with it?

--
Is it called a blow job because you inflate it with your mouth?

On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show flicker on lighting? Or couldn't they just use DC lighting?

--
Is it called a blow job because you inflate it with your mouth?

In article , Uncle Peter wrote:
On Sat, 19 Apr 2014 20:38:37 +0100, Vir Campestris
wrote:

On 18/04/2014 13:39, Uncle Peter wrote:
On Fri, 18 Apr 2014 10:32:34 +0100, charles
wrote:

In article , Vir
Campestris wrote:
On 16/04/2014 19:17, Uncle Peter wrote:

But the frequency we choose will have an effect on the number of
frames
a second on TV, the speed of motors, etc, etc. And those things we
like
to be metric.

This is obviously why NTSC TV uses 29.97 frames per second.


It was 29.94 in my day. Inflation affects everything.

AFAIK the Hz ain't that accurate, it fluctuates. But the electric
board are supposed to maintain a precise average for things like
clocks that are based on it (although I don't think anything is
nowadays).

NTSC is that accurate. It's the mains that isn't.

And, yes, the mains is accurate over 24 hours.

So how did TVs work properly when they used the mains as a guide to
frequency?

for B&W high stabilty wasn't needed.

--
From KT24

Using a RISC OS computer running v5.18

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the incoming
AC, the flicker would have been exactly the same.

--
Tciao for Now!

John.

On 19/04/2014 22:03, Tim Streater wrote:
In article , Uncle Peter wrote:

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal
hold. Is
this anything to do with it?

Don't think so. I think that was just a manifestation of the fact that
component drift with temperature was worse back then. More recent CRT
tellies didn't have them - or they could lock on better.

The latter. That and better temperature control inside the box due to
using solid state components instead of valves.

--
Tciao for Now!

John.

On Sat, 19 Apr 2014 22:47:34 +0100, charles wrote:

In article , Uncle Peter wrote:
On Sat, 19 Apr 2014 20:38:37 +0100, Vir Campestris
wrote:

On 18/04/2014 13:39, Uncle Peter wrote:
On Fri, 18 Apr 2014 10:32:34 +0100, charles
wrote:

In article , Vir
Campestris wrote:
On 16/04/2014 19:17, Uncle Peter wrote:

But the frequency we choose will have an effect on the number of
frames
a second on TV, the speed of motors, etc, etc. And those things we
like
to be metric.

This is obviously why NTSC TV uses 29.97 frames per second.


It was 29.94 in my day. Inflation affects everything.

AFAIK the Hz ain't that accurate, it fluctuates. But the electric
board are supposed to maintain a precise average for things like
clocks that are based on it (although I don't think anything is
nowadays).

NTSC is that accurate. It's the mains that isn't.

And, yes, the mains is accurate over 24 hours.

So how did TVs work properly when they used the mains as a guide to
frequency?

for B&W high stabilty wasn't needed.

Surely if you're slightly off, the picture would fall off the edge of the screen?

--
How is it one careless match can start a forest fire, but it takes a whole box to start a campfire?