By C. Robert Paulson, Television Microtime, Inc.
Several VTR formats incorporating both monochrome and color performance are now being used in CATV systems for program production, duplication, and playback. (Figure 1.) The 1/2-inch and 3/4-inch formats offer the benefits of relatively low cost, portability, operating simplicity, reasonable reliability, long tape and head life, and subjectively satisfactory picture quality, compared to l-inch and quad "broadcast standard" VTRs. The three-quarter inch cassette format is also attractive because of the availability of libraries of "software" for purchase or rental, as well as its simple slot loading and automatic programming features.
However, these VTRs have well-known time base instability and head switching dropouts or discontinuities. And to get a share of audience on the company free or pay-program channels (a necessary prerequisite for making money) the operator must distribute as stable a signal on these local origination channels as is available on the TV station originated channels.
Up to this year, the only solution to the problem of unstable pictures was to buy a stable (much more expensive) VTR. And if you wanted to do any fancy program production mixing tape and camera pictures, you bought an even more expensive VTR with a built in time base corrector.
"Broadcast quality" VTR costs--their size and complexity--the need for highly skilled technicians and lots of maintenance time--no interchangeability among l-inch VTR formats--all these factors worked together to foster the CATV industry's "standardization" on the 1/2-inch EIAJ and 3/4-inch u-matic formats. But now you've discovered a new set of problems, which require a time base corrector in these VTRs for their solution.