29-01-2020, 04:30 PM
The arguments for vision polarity and sound modulation can get very detailed. The basics for vision are:
+ve vision allows you to fully use the non linear part of the transmitter characteristics for sync pulses. So you get better TX efficiency. Deosn't help so much for colour where vision information goes below black.
+ve vision means that impulse interference doesn't affect syncs. The white spots can be reduced to some extent by an interference limiter circuit. With -ve vision impulse interference is hardly visible but can affect sync. This is largely sorted by flywheel sync.
Good AGC is easier with -ve. Good AGC for +ve needs more complex gating circuits to measure the black level.
+ve vision allows you to fully use the non linear part of the transmitter characteristics for sync pulses. So you get better TX efficiency. Deosn't help so much for colour where vision information goes below black.
+ve vision means that impulse interference doesn't affect syncs. The white spots can be reduced to some extent by an interference limiter circuit. With -ve vision impulse interference is hardly visible but can affect sync. This is largely sorted by flywheel sync.
Good AGC is easier with -ve. Good AGC for +ve needs more complex gating circuits to measure the black level.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
