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Down converted color subcarrier
(626.953 kHz)
FM signal band
4.8
Frequency (MHz)
Syne tip
pee
peak
Dark clip level
White clip level
{40%bee-100%1 60%
Fig. 1-6
Recording spectrum
1.3.6
FM Signal Recording Amp. Characteristics (REC
AMP)
Current:
More than 3.8 MHz: Optimum saturation recording cur-
rent
2 MHz
:34£1¢dB
1 MHz
:641dB
Less than
1MHz_:
Flat characteristics
Note: 0 dB at 3.8 MHz
1.3.7
FM Signal Head Current (VIDEO HEAD)
It shall be within 1.5 dB of 4 MHz optimum recording cur-
rent,
Azimuth
video head + 6°
Color signal playback system
1.4
LUMINANCE SIGNAL PLAYBACK SYSTEM
This system functions to return the signals recorded on the
tape to a form as close as possible to the video input signals.
The simplified block diagram is shown in Fig. 1-7.
The low level FM
signals played back by the two video
heads are combined into a single FM signal by the switching
amplifier.
After
amplification
to the required
frequency
characteristic,
a highpass
filter attenuates the down con-
verted color signal and passes only the FM luminance signal.
This HPF has the same response as that of the recording
system.
Variations in the playback FM signal level due to mechanical
stretching and contraction of the tape, and irregularities in
tape to head contact, are corrected by the limiter circuit.
The signal is amplified more than 80 dB to permit precise
demodulation. A double limiter circuit is employed in order
to prevent black/white reversal effects.
In the following stages, the demodulator and lowpass filter
return the luminance signal to its AM form. The de-emphasis
circuit reverses the emphasis applied during recording. From
this point, the signal goes to the mixer where it is mixed
with the playback color signal to become the video output
signal.
Video output signal
(Color TV signal)
Fig. 1-7
Luminance signal playback system
1-5
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