a-
E
5
Phase
AngIe Measurements
In
multi-channel
recorders
the angle
of the head
gap
relatlve
to the
direction
of tape movement
not only affects
the high frequency response
but
also
the
phase
angle between channels.
This
phase
angle depends
much more crltically on
the
gap
allgnment than the output
level
at
high fre-
quencies.
The
phase
angle
ls determlned
by means
of
sultable
measurements of output levels.
E 5a
Measurement of
the Phase Angle Between
the Replay
Channels
The
measurement should be
made by means of the output
levels on
channel
I
and
4 when
playlng
the
azlmuth
section of
the test tape.
Flrst check
that the output levels of both
channels are equal ard lf
necessary make them equal by
means of the
galn
controls
on the
playback
amplifiers
(
see
D 3
).
Pr
=
P4
[db]
Next the two outputs should
be
connected
ln serles in-phase and
the resultant sum-Ievel P"
should
be
measured. Finally the output termlnals
of one of the two channels should be
reversed
so as
to connect them
in
serles antl-phase
ln order
to measure the dlfference level
P6
Fig. L7
Measurement
of
p
Iao]
Fig. 18
Measurement
of P4
[oo]
By
subtractlng
the two measured levels one obtalns
P"6=P"-P6
The
phase-angle
between the two channels can be
found from fig. 18 from
this
value P"6.
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