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"The function of the reactance tube is to compare the incoming burst to the phase of the local subcarrier, and 'nudge' it into phase so the signals match each other. It does this by varying the load on the crystal."
Slight correction: The reactance tube does not do the comparing - this is done in a preceding burst phase detector. The output of the phase detector is a varying DC that is input to the reactance tube.
A little more on the purpose of the 3.58 trap in a color set. Not only does it reduce the visibility of dots; it prevents a brightening and washout of color saturation in highly saturated areas. This effect would occur because the picture tube is nonlinear, so any high frequency dot pattern would be partially rectified by the picture tube and result in a local brightening of the area where the color subcarrier is strong.
Depending on the phosphor dot structure of the color CRT, the chroma dots could also cause moire patterns. This was definitely true for the early Trinitron sets, which as a consequence used some of the strongest color subcarrier suppression of any set designs ever.
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12-24-2014, 08:26 PM
Hybrid Mode
