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In article ,
Mark Carver wrote:
charles wrote:

SECAM (SECquence Avec Memoire) (or commonly: Systeme European Contre les
AMericaines) is a French developed colour system that is broadcast in
France, most of its former colonies and was adopted (for political
reasons) by the Soviet Union (USSR).

Not entirely political, there was a good technical reason too, some of
the signal paths are incredibly long in Russia/ex-USSR.
SECAM is better suited than PAL or NTSC because the chrominance signal
exists in the FM domain, and therefore will not degrade as rapidly as AM
based PAL and NTSC colour coding.

Well before the adoption of SECAM, the BBC had demonstrated that even NTSC
could be sent happily from London to Moscow and back without degradation.
On radio links subject to fading, such as the trans (English) Channel,
SECAM suffers serious problems in that the luminance amplitude fades but
the chroma decodes to its intended value. We used to see that at TV Centre
when we transcoded SECAM signals to PAL.


I'm in an ex-Soviet country right now, and my hosts verify it was more
of a technical decision than political (according to them :-) ).

they would say that, wouldn't they?

Of course the TV studios in Russia actually make their programmes in PAL ;-)
It's possible to mix coded signals with PAL, for SECAM you need an RGB
mixer ;-(

The political decision is quite obvious when you realise the Cold War was
at its height. NTSC was from the USA and PAL was from Germany. Since
France had just left NATO and the General was visiting Moscow to create a
Franco-Soviet pact, the decision to use SECAM came out of that visit.

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

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charles wrote:
In article ,
Mark Carver wrote:
I'm in an ex-Soviet country right now, and my hosts verify it was more
of a technical decision than political (according to them :-) ).

they would say that, wouldn't they?

Of course the TV studios in Russia actually make their programmes in PAL ;-)

Not any more, just about all digital component now, so SECAM only
appears at the final stage, at the transmitter site. In fact, on my
travels there's really only one country and broadcaster left that still
has PAL elements in their Tx chains, some BBC English regional studios.

It's possible to mix coded signals with PAL, for SECAM you need an RGB
mixer ;-(

Indeed, some SECAM stations used to take the signal down to YUV, that's
not quite as 'hairy' as doing it in RGB.

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Ian Jackson wrote:

Haven't some of the ex-Soviets now switched to PAL?

Some have, others have kept SECAM for terrestrial analogue, which just
as in the UK and W Europe is on its way out anyway.

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Ian Jackson wrote:


But aren't things like microwave links FM anyway?

They are, but you still need to consider the triangular noise spectrum,
when transporting 'AM' signals within an FM environment.

A prime example is the stereo difference channel, in the Zenith Pilot
Tone radio system, we've all witnessed how disproportionally noisy that
gets once the signal becomes weaker. The difference channel is
essentially AM at baseband.