Mark You forget the most important difference from which PAL takes its name. The alternating phase of the colour subcarrier each line. To overcome the colour errors that reflections cause in the NTSC system, the PAL system puts a 180° phase shift in one of the two chrominance modulating components each line. In the receiver a one line period delay line, originally an acoustic glass delay line but now done digitally, is used to average the colour signal over two lines. This means that phase shifts caused by reflections and which last for more than 128µs cancel out. This reduces vertical colour resolution but since horizontal colour resolution has been filtered down to reduce the chrominance bandwidth this is not a very peceivable degradation and well worth it for the colour stability. This better system was the result of being late into colour television system after North America had found the problems, It's the second mouse that gets the cheese! A result of this system needing a very accurate line delay (to within small fractions of a subcarrier period) is that both the vertical and horizontal synch locks are very tight on monitors and recievers built for PAL colour and even if you go in at baseband video via the "SCART" socket found on most sets, they will not lock up the NTSC derived baseband video as monitors used to do in monochrome days. I used to work designing telvision equipment such as standards converters and it is no small problem.
Nick Rouse ----- Original Message ----- From: "CARTER" <> To: "'Tony J. O'Hara'" <>; "Bailey, Jeff" <[email protected]> Cc: "'emc-pstc'" <> Sent: Tuesday, July 25, 2000 10:47 PM Subject: RE: 8591EM monitor output > > > The differences between PAL & NTSC go way beyond modulating RF. Even at > baseband, the monitors will be different & one may not work with the other's > signal. The Frame rate, or vertical interval is different - NTSC based on > North American AC at 60 Hz, as opposed to European 50 Hz, and the Horizontal > sync is different, as a result of being harmonically related to the vertical > sync. There is an issue (probably not with the signals in question) with the > color sub-carrier frequency offset from the video carrier, and the fact that > (because of the aforementioned) the video (baseband) bandwidth for PAL is > much wider than NTSC. A monitor may work with the other format if it is a > little forgiving (has some slop built into the sync'ing circuits). Give it a > shot with whatever is on hand, then go shopping if need be. > > IMHO > _\\|//_ > (' O-O ') > ooO-(_)-Ooo > > Mark Carter > AM Communications, Inc. > [email protected] <mailto:[email protected]> > Voice: 215-538-8710 > Fax: 215-538-8779 > > > -----Original Message----- > From: Tony J. O'Hara [mailto:[email protected]] > Sent: Tuesday, July 25, 2000 12:24 PM > To: Bailey, Jeff > Cc: 'emc-pstc'; '[email protected]' > Subject: RE: 8591EM monitor output > > > > A modulator for PAL is different than NTSC! PAL receivers use different > frequencies and I also think there are other differences!) . However, I > would assume that if you're in a locality that has PAL receivers then you > should be able to easily get a PAL modulator. > Remember also, that most "new" (last 5 years or so) receivers (at least US > NTSC ones) have a base-band video input (making them also a monitor!), then > you wouldn't need a RF modulator! > Tony > Colorado > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
