Pioneer tuning fork Service Manual page 16

Then the brightness of 3.58MHz dots is inverted line by
line and frame by frame and is made insensible. To avoid
beating interference between the colour and sound carriers,
the horizontal scanning frequency has been determined at
15,734 ( 1 5 , 7 5 0 - 1 6 ) H z .
The transmitting method of composite chrominance signal
by placing its bands of energy between those of luminance /
PAL S Y S T E M
N T S C and P A L employ Q . A . M . system of chrominance
signal. They transmit two chrominance
simultaneously, employ a synchronized detector, and hue
and chrominance saturation are determined by phase
difference and relative level between the burst signal and
chrominance signal.
There are, however, some differences between them. P A L
uses simple weighted ( R ' - Y ' )
difference signals of equal bandwidth to modulate the two
K,G
l,L
0.75
1.25
Fig. 3 Bandwidth of European 625-line System for
Bands IV/V (Channel Width: 8MHz).
P A L receiver adds and subtracts the direct and lH-delayed
signals. Adder and subtractor put out (B - Y) and (R - Y)
signals respectively. The demodulated signal becomes an
average between the two adjacent lines. Thus the resolution
becomes a little lower than that of NTSC in principle, and
the modulating circuit becomes complicated. P A L system,
however, has a higher allowance in phase distortion in the
transmission system.
The P A L system nullifies hue error or the phase error of
color signal. If the transmitted signal is magenta for sever­
al scanning lines and is subjected to a phase lag of 0°, the
vectors of a pair of received lines will be as E l and E2 in
Fig. 5. The even or odd lines inverted by a transmitter are
reinverted by the receiver and the lower line of the pair leads
from the original phase as E2\
integrated and averaged visually or electrically, the phase
error is nullified. If the error is large, the integration be­
comes difficult and color moves up and down (Hanover bar
or Venetian blind).
14
information
and (B' - Y') color-
/
G
I
L,K
/c-4.43
MHz
urn
•1.1
1.6-
When E l and E 2 ' are
signal is called "interleaving". The luminance and carrier
color signals ( E , E n) are represented by the following
Y C
equations:
E = 0J0E + 0.59E
Y R G
ECN = a(E — Ey) cos oost -h b(E
R
a: 0.877, b: 0.493, f :
s
quadrature phase (but equal frequency) subcarriers while
NTSC system employs complex I and Q signals which have
unequal b a n d widths.
The most significant difference is in modulating method.
P A L ' s modulation axis of ( E
that of N T S C does not. The carrier color signal is represent­
ed by the following:
ECP = ± Q(ER — EYJcosodSt + b(Es —
Burst
Color subcarrier
Burst
n line (n+1) line
E - E
R Y
Fig. 4 PAL's Transmission Vectors
Reiverted lower line of a pair
(reddish magenta)
+ V
Transmitted original hue magenta
E'2
Ei
Received upper line of a pair
(bluish magenta)
Received lower line
E2
Fig. 5 Phase Error Correction with the PAL system
+ 0.11E
B
— E )sin o)St
B Y
3.58MHz
- Ey) inverts every 1H while
R
E )sinwst
Y
(n+2) line
+ U