From: utzoo!decvax!duke!harpo!eagle!karn Newsgroups: net.video Title: Re: taping from VCR to VCR Article-I.D.: eagle.735 Posted: Thu Jan 20 18:46:18 1983 Received: Sun Jan 23 07:39:34 1983 References: bunker.200 rocheste.458 The methods used for on-air and cable channel scrambling are quite different from "copyguard" (TM?), and none that I know of distort vertical sync - they all work by screwing up horizontal sync. Oak's ON-TV system uses a sine wave turned off during the vertical interval (to prevent transmitter overmodulation), while WHT in Newark and most cable systems use a simple square wave ("posthole") sync suppression scheme. The sound is usually on an FM subcarrier (like SCA on FM broadcast stations) or a suppressed-carrier DSB subcarrier (like the stereo difference info in FM broadcasting). On a related topic, does anyone have info on HBO's satellite scrambling scheme? I suspect strongly that they will be going to digital audio (notice their newly proclaimed stereo ability). I also think that going digital, even without high speed encryption, will be enough to deter most "pirates", so there may be some hope for those of you with knowledge of digital modulation techniques. Phil