Page 30 - 2015-12

The VTR was a Sony CV-2000. The
selling price was in excess of
$1000.00 (average weekly wage at
the time was about $80.00 per
week). The VTR used seven inch
reels of half inch video tape, run-
ning at a tape speed of 7½ inches per
second (IPS), providing just on one
hour of record/play time. Only the
basic record – play functions, plus
rewind and forward were available.
The image quality was pretty poor
by today's standards, giving around
200 lines of horizontal definition, Above: An early model Shibaden (Japanese) reel to reel VTR,
but TV screens were somewhat with built-in tuner and monitor.
smaller then. The VTR was just a
little larger, but a lot heavier than a conven- around the video drum, and held in place by
tional audio reel to reel recorder of the time. guides. The heads are placed on the drum in
The extra weight was mainly due to the rotat- such a way that as one head is leaving the
ing video head drum and the higher precision surface of the tape, the other is starting its scan
of the mechanics. across it. By switching from one to the other,
continuous tape contact is maintained. The
Why a rotating video head? tape heads move across the tape at a shallow
To reproduce a reasonable quality video im- angle, recording a long diagonal track across
age, at least 200 lines of horizontal definition the tape. This allows an entire frame to be
(Sony CV-2000) is required. With the PAL recorded per track, which simplifies the
system, one scan line takes 64 microseconds electronics and timing systems in the machine,
to scan from left to right of the TV screen. To as it also allowed the recorder to be "paused"
get 200 lines resolution, the video must be ("freeze frame") during playback to display a
capable of being turned on and off 200 times single still frame, by simply stopping the tape
during that 64 microsecond scan, the video transport mechanism and allowing the heads to
frequency to do this can be calculated as repeatedly pass over the same track.
64/200 microseconds, which equals 3.125
megahertz. For correct playback, the rotation of the heads
has to be precisely synchronized with the mo-
As the average reel to reel audio recorder tion of the tape through the tape path, so a
(which uses a stationary head) running at 7½ "control track" of synchronizing pulses is re-
IPS is hard put to achieve a top frequency corded, along with one or two audio channels.
response of 20 kilohertz. To achieve a higher
frequency, a much higher tape speed would be Other manufacturers of VTRs
needed. In a VTR / VCR, this is achieved by Although Sony was a leader in the VTR mar-
placing the video heads on a drum, wrapping ket, there were several other brands available,
the tape around it, and rotating it as well as some with a built-in monitor screen. The intro-
moving the tape, giving a much higher duction of a timer permitted the recording of
"read/write speed". off-air material without the presence of the
operator. However, the one hour recording
Most domestic video recorders use a two head limit did pose problems.
video drum with a little over 180 degrees of
tape wrap. The tape is wrapped longitudinally

30 REEL DEALS December 2015