Pioneer tuning fork Service Manual page 48

1 2 . Tuner
VCR has a TV tuner a n d an antenna selector for record­
ing a TV program a n d an R F converter for putting out
TV signal. With the tuner, it is possible t o view a program
while recording another. The input signal can be put out
to the V I D E O O U T terminal directly, after modulation
and demodulation, or after recording and playback. Hi-fi
VCR equips a multisound decoder a n d generally employs
split-carrier system t o achieve hi-fi sound reproduction. It
also has a synthesizer-channel-presetter for easy channel
presetting, microcomputer controlling and timer-activated
recording.
^Split-carrier system: Sound signal is separated from
ture signal before video demodulation.
carrier system, which separates
1 3 . V i d e o C a m e r a
The image coming through the lens is focused on a photo­
electric device. The light information transduced into elec­
tric one is scanned line by line in t h e same way as TV
receivers d o . There are several kinds in the photo-electric
device, camera tube a n d solid imagers.
14. 1 / 2 " Hi-fi V C R
1/2 hi-fi V C R has a n additional audio recording system
to the conventional system. Therefore, dubbing or su­
perimposing completely independent 2-channel audio sig­
nals on the audio tracks is possible while recording a video
program.
The VCR's conventional audio recording system sacrifices
sound quality because the audio head is stationary and the
tape-to-head velocity is low. Hi-fi VCRs have solved the
problem by recording audio signal through rotating heads
which make the tape-to-head velocity high.
1 4 . 1 0 Hi-fi ( N T S C only)
14.1.1 Standard p Hi-fi
13 Hi-fi system records audio signal on the diagonal video
tracks together with video signal. It shifts the Y-carrier u p
by 400kHz and inserts four separate F M audio carriers be- /
FM de­
Y signal -
modulation
Dowm-
C signal-
conversion
FM
de­
Audio -
modulation
46
pic­
Unlike the inter-
sound signal after the/
Mixer
Video/audio head
Fig. 3 4 Recording System of 0 Hi-fi VCR
demodulation, this system provides
pressing video signal interference.
UHF ant.
UHF j
UHF out
distributor
I
VHF ant.
T distributor
j
RF
Modulator Modulator
VHF out
Fig. 3 3 Antenna Selector
tween the C- and Y-signals in the frequency spectrum. Two
carriers 1.38MHz fi (LA) and 1.68MHz fs (RA) are
recorded at a time through the A-video-head and 1.53MHz
f2 (LB) and 1.83MHz U (RB) through t h e B-video-head.
Cross-talk can be suppressed because of their frequency
difference. The audio tracks at the top can be used as ever.
Therefore, dubbing is possible on a hi-fi VCR through the
stationary audio head. In playback, switching the picked-
up signals coming from the A- a n d B-heads are made be­
fore or after demodulation.
14.1.2 Super 13 (High-band 0)
V C R ' s picture resolution depends on the recording fre­
quency bandwidth which depends o n the carrier frequency.
When the carrier frequency is shifted u p by 400kHz, the
resolution increases by 30 lines theoretically.
The frequency bandwidth of (3 VCR is wider than that of
V H S VCR because the tape-to-head velocity of the form­
er is higher t h a n the latter. (3 Hi-fi has already shifted the
Y-carrier u p by 400kHz t o avoid F M audio interference.
Super (3 system shifts the carrier u p further 400kHz,
800kHz in total, improving the effective resolution by
aproximately 3 0 % compared with the conventional non-
hi-fi system.
Audio
C
688kHz
h
hi-fi sound by sup­
Video
Front
IF
End
Audio
IF
Video
' Audio
Y
3.6MHz 4.8MHz
1.38MHz(LA)
A
/ = 1.53MHz(LB)
2
/ =1.68MHz(RA)
3
/ = 1.83MHz(RB)
4