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3.
Set attenuator
#1 to 40
DB
,
and attenuator #2 to
0 DB
.
NOTE
:
With a 10
-
volt input
,
and
attenuator # 1 set
for
40
DB
attenua-
tion, the output
at attenuator
#1
will
be 100 millivolts.
4.
On the Model
416A, set the
EXCESS
COUPLER
LOSS
switch
to 0 DB.
5.
On the Model
416A,
adjust
variable res
i
stor R94
to obtain a zero
meter
indication
.
The R94 adjustment is located
on
the top deck of the instru-
ment, and
is
identified
in
Fig
.
20.
6.
Leave the test set
-
up
intact,
and perform
the
Electrical
Full
Scale Adjustment.
Electrical Full Scale Adjustment
-
1.
Set the Model 416A
on its
left (with
respect to the
front of the
con
-
trol panel) side so that the bottom deck of
the ins
t
rument will be accessible.
·
2
.
Set attenuator #
1 to
46 DB
.
3.
On
the
Model
416A
,
set the
RANGE
switch to the
0 DB 100% position
.
4.
Connect the
external voltmeter
to
the input side
of
capacitor
C2 7.
C2 7
is
on the bottom deck of the Model
416A and is identified in
Fig
.
21.
The
input
side of C27
is connected to terminal strip TSl
,
also identified in
Fig
.
21
.
(Do NOT
connect
the
voltmeter
to p
i
n 1
of
V5
.
)
Set
the voltmeter
to
indicate
on the
.
3
volt range.
5.
At the audio oscillator
,
vary the frequency to
obtain peak indica
-
tion
on
the voltmeter connected to
C2
7
.
6.
The
voltage at
C27 should be
approxi
mately 100
millivolts or
slightly greater
.
If
necessary,
adjust attenuator #1 to
obtain
a voltage
of
this level.
(A
typical
voltmeter indication at this point might
be
120
.
0 milli
-
volts.)
Record the
voltmeter indication
,
to the
thi
rd significant figure
,
as
11
incident volts''
.
7.
On the Model 416A
,
disconnect
the incident input
cable
and
connect
the reflected
input cable
.
8.
Adjust the SET
TO
FULL SCALE
control
on
the
Model
416A to
ob
-
tain a
voltmeter indication
of 1
.
44 times the
i
ncident volts reading
(
±
1
%)
ob
-
tained in step 5
.
9.
Reconnect the
incident input
cable
to the INCIDENT /REFERENCE
connector on
the
Model
416A
.
Note the
v
oltmeter
i ndi
cation
,
and
record
it
as Voltage
A
.
(This resultant
voltage
,
present at the input
to
capacitor
C2 7,
corresponds to
Voltage
A
as
shown
in
F
i
gs
.
3 and 5
.
) A typical Voltage
A
reading
might be 174 millivolts
.
-
53
-
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