Pioneer tuning fork Service Manual page 41

7. Cross-talk Suppression
The following methods are taken to suppress cross-talk
caused by guard-bandless recording.
7 . 1 Y-signal cross-talk suppression
7.1.1 Azimuth recording
To produce the maximum output, the orientation of the
Playback-head should be the same to that of Recording-
head with respect to the tape direction or track direction.
The azimuth, or orientation of head-gap, of A C R should
be at a right angle (0 azimuth) t o the tape. As mentioned,
each of the A- and B-heads records picture information
of one field. The orientation of the gap of video heads is
intentionally made off-azimuth or tilted a little in o p p o ­
site direction each other (0: ± 7 ° , 8mm: ± 1 0 ° , V H S :
± 6 ° ) . Then the azimuth difference between the A-head
and B-head becomes 14° in 1/2" 0, that makes A-head
sensitive to the signal o n the A-tracks and not to the sig- /
Head direction
Gap
Head B
Azimuth of
head B
Fig. 21 Azimuth Recording
3.4MHz
4.4MHz
Fig. 2 0 Azimuth Loss
Gap Track width
Head A
VHS : 9 = ±6°
Azimuth of
head A
Trackwidth
nal on adjacent B-tracks, and on the other hand it makes
B-head sensitive to B-tracks a n d insensitive t o A-tracks.
This azimuth effect suppresses the crosstalk from adjacent
tracks when there is n o guard-band. This method is effec­
tive t o Y-signal because the azimuth effect increases as the
signal frequency increases.
Azimuth effect: The played hack signal is decreased or lost
in high frequency range if the orientation
playback head is not the same as that of recording
The larger the orientation
heads, the smaller the reproduced
629kHz
A z i m u t h
Fig. 2 2 Cross-talk Characteristic at 1 4 ° Azimuth
Difference
of the gap of
head.
difference between the two
signal.
Track width": 6ju
Azimuth : 90°
/(MHz)
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