Old fashioned questions

I've been asked for info by someone about the old 'analogue' TV, but which
by extension make me wonder about the equivalent for the current digital
transmissions.

What was the frequency stablility, in practice or mandated, for the nominal
carrier for UK PAL transmissions? And was this much the same in other
countries (inc non-PAL ones)?

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article ,
Jim Lesurf wrote:
I've been asked for info by someone about the old 'analogue' TV, but which
by extension make me wonder about the equivalent for the current digital
transmissions.

What was the frequency stablility, in practice or mandated, for the
nominal carrier for UK PAL transmissions? And was this much the same in
other countries (inc non-PAL ones)?

1 part in a million was all that the PAL spec required, but in practice, in
the UK, was far better than that.

SECAM was, ISTR, only 1 part in 10,000

--
From KT24

Using a RISC OS computer running v5.16

charles wrote:
In article ,
Jim Lesurf wrote:
I've been asked for info by someone about the old 'analogue' TV, but which
by extension make me wonder about the equivalent for the current digital
transmissions.

What was the frequency stablility, in practice or mandated, for the
nominal carrier for UK PAL transmissions? And was this much the same in
other countries (inc non-PAL ones)?

1 part in a million was all that the PAL spec required, but in practice, in
the UK, was far better than that.

Yep, about 4.43 times better

From IBA COP 1977 Section 2.

Quote:-

2.5 Colour Subcarrier Frequency

4.43361875 +/- 1 Hz

Where the signal originates from an overseas source, this tolerance may be
relaxed to +/- 5 Hz

The maximum rate of change of s/c freq shall be 0.1 Hz/s

During source synchronising operations there will be small phase perturbations
which may cause the freq and its rate of change to deviate beyond these limits
for short periods (1-5 seconds)



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

www.paras.org.uk

In article , Mark Carver
wrote:
charles wrote:
In article , Jim Lesurf

IIUC the details below are for the PAL subcarrier. But what about the main
carrier for the video?

Slainte,

Jim


What was the frequency stablility, in practice or mandated, for the
nominal carrier for UK PAL transmissions? And was this much the same
in other countries (inc non-PAL ones)?

1 part in a million was all that the PAL spec required, but in
practice, in the UK, was far better than that.

Yep, about 4.43 times better

From IBA COP 1977 Section 2.

Quote:-

2.5 Colour Subcarrier Frequency

4.43361875 +/- 1 Hz

Where the signal originates from an overseas source, this tolerance may
be relaxed to +/- 5 Hz

The maximum rate of change of s/c freq shall be 0.1 Hz/s

During source synchronising operations there will be small phase
perturbations which may cause the freq and its rate of change to
deviate beyond these limits for short periods (1-5 seconds)

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On Fri, 09 Sep 2011 17:54:46 +0100, Mark Carver
wrote:

I've been asked for info by someone about the old 'analogue' TV, but which
by extension make me wonder about the equivalent for the current digital
transmissions.

What was the frequency stablility, in practice or mandated, for the
nominal carrier for UK PAL transmissions? And was this much the same in
other countries (inc non-PAL ones)?

1 part in a million was all that the PAL spec required, but in practice, in
the UK, was far better than that.

Yep, about 4.43 times better

I think he was asking about RF, not subcarrier.

On 09/09/2011 16:37, Jim Lesurf wrote:
I've been asked for info by someone about the old 'analogue' TV, but which
by extension make me wonder about the equivalent for the current digital
transmissions.

What was the frequency stablility, in practice or mandated, for the nominal
carrier for UK PAL transmissions? And was this much the same in other
countries (inc non-PAL ones)?

Slainte,

Jim

The only value I can remember is for precision working and that is of
the order of plus or minus 1Hz from the specified frequency. Made
frequency measurements a bit difficult as it needed an rubidium standard
to be carted around.

Precision working was often done between the UK and France for main
stations sites to reduce the visibility of the interference. I think it
gave another 10dB protection.

Phil

In article ,
phil wrote:
On 09/09/2011 16:37, Jim Lesurf wrote:
I've been asked for info by someone about the old 'analogue' TV, but
which by extension make me wonder about the equivalent for the current
digital transmissions.

What was the frequency stablility, in practice or mandated, for the
nominal carrier for UK PAL transmissions? And was this much the same in
other countries (inc non-PAL ones)?

Slainte,

Jim

The only value I can remember is for precision working and that is of
the order of plus or minus 1Hz from the specified frequency. Made
frequency measurements a bit difficult as it needed an rubidium standard
to be carted around.

Precision working was often done between the UK and France for main
stations sites to reduce the visibility of the interference. I think it
gave another 10dB protection.

and UK & Ireland. I think Presely (or perhaps Carmel) had a high stability
frequency source.

--
From KT24

Using a RISC OS computer running v5.16

On 09/09/2011 18:08, Jim Lesurf wrote:

IIUC the details below are for the PAL subcarrier. But what about the main
carrier for the video?

From memory it was ±500 Hz except where precision offsets were used, in
which case it was ±1 Hz. For System I the sound carrier offset was
+5.9996 MHz ±500 Hz.

--
Andy

On 09/09/2011 16:37, Jim Lesurf wrote:
I've been asked for info by someone about the old 'analogue' TV, but which
by extension make me wonder about the equivalent for the current digital
transmissions.

What was the frequency stablility, in practice or mandated, for the nominal
carrier for UK PAL transmissions? And was this much the same in other
countries (inc non-PAL ones)?

Slainte,

Jim


A walk around durris Main TX site reveals several GPS antennas on the wall.

I think they use GPS-derived frequency references nowadays, which are
good to something like 1x10-13 or somesuch whist GPS-locked. They are
less accurate when they loose GPS lock and revert to Quartz Xtal.

From a quick google,here's an example of a Freq Refererence unit:
http://www.endruntechnologies.com/fr...andard-gps.htm

It seems you get certain 'standard' frequency reference boxes, like
10Mhz which you then use to synthesise the frequency you need.

--
R

On 9 Sep,
Jim Lesurf wrote:

IIUC the details below are for the PAL subcarrier. But what about the main
carrier for the video?

We worked to 1kHz, but corrected if worse than 500Hz, usually to as close as
possible, 30 Hz ring a bell for main stations.

Relay stations would generally have the errors of their parent station plus
their own, but some later transposers phase locked their output to their own
reference. Spec was still 1Khz.

--
BD
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