From Newsgroup: uk.telecom
Op 2-2-2026 om 18:56 schreef David Woolley:
On 02/02/2026 15:14, The Natural Philosopher wrote:
Take analogue TV, the audio may be considered to be on a separate
transmitted frequency, but the chroma is-a multiplexed onto the same
'channel' as the video.
The way it is specified, and the way that analogue TVs recovered the
audio, is that both audio and chroma are on sub-carriers, not one on a sub-carrier, and one as an adjacent carrier.
An analogue tv signal was transmitted via two transmitters:
One for video (vestigal sideband modulation) on the channel frequency,
One for audio on a frequency 5,5 or 6 MHz higher than video frequency.
Some TV systems used FM for audio, some used AM.
Later the BBC used NICAM for audio. (was NICAM on another frequency?)
Tugether they form the "TV-channel", with a bandwidth of about 7 MHz.
In VHF the channel width was 7 MHz (for B & G),
in UHF 8 MHz.
Chroma was modulated on a subcarrier with an exact frequency of +
4.43361875 MHz for PAL.
More info here:
<
https://en.wikipedia.org/wiki/Analogue_TV>
Analogue TVs recover the
audio as a 6MHz signal, embedded within the demodulated vidwo, and feed
it into a 6MHz IF amplifier; they don't down convert to, say, the
10.7MHz IF typically used for FM broadcast sound.
Analogue TV receivers use an Intermediate Frequency.
For B and G-system, as used in The Netherlands and Germany
this IF filter was from about 33 to 40,5 MHz.
You were tuned correct if the video carrier was on 38,9 MHz
and the audio carrier on 33,4 MHz (B & G audio was on +5,5 MHz).
There was no 6 (or 5,5) MHz IF amplifier,
the audio was demodulated from 33,4 MHz in case of B/G.
(Note that 6Mhz is for the UK.-a Other sub-carrier frequencies were used
in other countries.)
Chroma is interesting, because, if you treat it as a single sub-carrier,
you have to treat the modulating signal as being a complex number.
I'm not sure what you mean with this.
Rink
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