Table of Contents
Advertisement
=.
v'-
Y
v
Procedure:
l.
With the
equipment
connected
as
shown
in
Fig.
3-5, set
the
signal-generator
controls
as follows:
Frequency
.
.
Specified
frequency
of
ceramic
filter.
See
Tabte
3-
l.
Modulation ..
.
Fm,400Hz,75kHz
deviation
(
100%)
Output
level .
.
1,000rrV
(60
dB)
2.
Set
the tuner
switches
as
f«rllows:
FUNCTION
switch
F-M
MODEswitch..
...
MONO
3. Adjust the
signal generator
frequency
slightly to
obtain
a
ntaximum
output, then
change
the
signal generator
modulation
to
a-m, 4OOHz
3Wo.
4.
If
the
discriminator transformer
IFT2OI is
not
aligned
correctly,
400 Hz ripple
will
be
obseryed
as
shown
in
Fig.
3-6.
I
5.
Turn the
secondary
side core
of
discriminator
transformer
IFT20l
(see
Fig.
3- I
0) to
obtain
a
minimum indication on the
oscilloscope
with
an
alignment
tool
as
shown
in
Fig.
3-6.
Fig.
3-6.
Fm discriminator
alignment
output
response
Note:
Turn the core
carefully
and
slowly
because
the output
appearing
on
the
oscilloscope
jumps
up
and
down
when
turning
the
core.
This
might
cause
difÍï-
culty
in
determining
the
point of
mini.
mum output. Also,
at both
extreme
positions
of
the top
coÍe,
decreased
out-
put
will
be
observed. The real
null point
should
be
obtained
in
the middle
of
the
core thread
length,
and mar<imum
output
appeaÍs
at
each side
of
the true
null
point.
6.
Change
the
signal
generator
modulation
to
fm,
400
Hz,
I5
kHz
deviation
(
100%).
7
.
Turn the
core
of fm
IFTI
0l
and the
primary
side
core
of
discriminator transformer
IFT201
(see
Fig. 3-10)
to
obtain the
maximum output.
3.2.
FM
FREOUENCY COVERAGE
AND
TRACKING ALIGNMENT
Note:
Before
startirrg
this
alignment, the fm
i-f
and
discriminator alignment should
be
performed.
Test Equipment
Required
l.
Fm
signal
generator
2.
Ac
VTVM
3.
Oscilloscope
4.
Alignment tools
Preparation:
l.
Connect
the equipment
as
shown
in
Fig.
3-'l
.
2.
Set
the tuner
switches
as
follows:
FUNCTION
switch
FM
MODEswitch......MONO
Signal
Generator Method
Follow the
procedures given
in
Table
3-2
when
performing this alignment
with
an
fm
signal
generator.
Be sure
that
the dial
is
mechanically
calibrated.
Off-theAir
Signal
Method
F'requency coverage and
tracking alignment
can
also
be performed
by
utilizing off-the-air local
fm
signals.
However,
before performing the
alignment,
be
sure
that the dial is
mechanically
calibrated.
Adjust
+
t
h
Fig.3-5.
Fm Í-f
and discriminator alignment fesf setup
by
rf
signal generator
oscilloscope
ac
VTVM
0.O2ttF
sT-5066
0.02ttF
rf
signal
generator
r-
:J
V
7
Advertisement
Table of Contents
