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Originally Posted by oldeurope
But have a look at the data sheet attached:
minimum 87% typical 93% maximum 99% What value should we take?
And with the sound ist is the same, because it goes via the vision input of the other IC.
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If the modulator is like my design, the sound modulator is set to System I, negative vision mod, and the input is biased by a preset pot which acts as an adjustment for the sound/vision carrier ratio. With this arrangement, 100% sound modulation depth is not a problem, in fact it will go beyond 100% (inverted carrier)! This is because the peak sound power on 405 should be equal to the peak white vision power, but the modulator when working with negative mod, has more than peak white to sync tip range (as peak white is 20% carrier).