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voltage
source that represents
the
denom
i
nator
of
the ratio
to
be
measured to
the
connector
d
esignated
INCIDENT /REFERENCE.
(Without
this signal input,
when the
ratio
meter
is t
urned
on, the ratio
being
indeterminate, the meter
pointer
will flu ctu
at
e
markedly.)
2
.
Plug the power
cable
into a
pow
er
line
of spe
cifi
ed
voltage
and fre
-
quency.
Turn the
power
switch to
ON.
Allow the
instrument about
five minutes
to reach
a
state
of
stable
operation.
3.
Connect the voltag
e
source that represents
the
numerator
of the ratio
to
be
me
a
sur
ed
to
t
h
e
connector designated REFLECTED/PROBE.
4
.
Set
the
RANGE
switch
to
0 DB
100% and the
EXCESS COUPLER LOSS
switch to 0 DB
.
(The function of the
EXCESS
COUPLER
LOSS
switch is
discussed
in
the Appli cations
section.)
5.
Check that the tuning
eye (RF
POWER
MONITOR)
h
as
begun
to
close
but
is not
completely
c
lo
sed
.
a,
If the eye
does not move
t
oward
closure: ( 1) there is
insufficient
i
nput power
; i
ncrease the
i
nput level
at the
source.
Or (2) the
modulation
voltage
on the
signal
is
not
1
kc ±40
cycles; adjust
the
modulating
v oltage at
the source.
b
.
If
the eye
overlaps
by more
than 1/32
11
,
either of two conditions
(or
both
)
m
a
y need
c orrecti
on:
(
1)
Instrument
may
be on
too
low a
range;
check
that the
RANGE
switch
is
at 0
DB
100%; if at
0 DB
100%, and
the eye
is
closed
:
(2)
I
nput level
is t
oo
high
;
reduce
the
i
nput
level at
the
source.
6
.
Calibrate
the meter for full-scale indication.
Full
-
scale
calibration
u
sually
is
achieved
by providing
inp
u
ts of
known ratio (usually
100%), and adjust
-
ing th
e
SET TO FULL SCALE
control to
b
rin
g
the meter indication exactly
to
that
of
the known
ratio
(usually 1
00%
).
Two examples of calibration
procedure
are
given below.
Cal.~_
brating
to 100% reflecti
on
:
( l)
By externa
l
means
9
such
as
a voltmeter
,
measure
the
two
inputs,
and
s
o
adjust
the sources that the two
inputs enter
the
ratio meter
at t
he
same
leve L
(2)
Adjust the
SET
TO FULL SCALE
control
until the meter
indicates
exactly
100%
.
Calibr
ati
ng
to
les
s
than
100%
reflection
:
( 1)
Choose the
desired
ratio, 25%
for example.
By external means,
such
as a
voltmeter,
measure the two inputs
and
adjust
the
sources so
that
the level of
the signal which
reaches
the
Model 416A a.t REFLECTED/
PROBE is 25%
of
that which is
connected to INCIDENT /REFERENCE.
(2)
Adjust
SET
TO
FULL SCALE to obtain
a
meter
indication
of exactly 25%.
-5-
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