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4.
Connect a Model X421A
Waveguide
Crystal
Detector
Mount
to the
sec -
ondary arm of
each coupler.
5.
Connect the Model X281A adapter to the R
.
F
.
OUTPUT on the Model
670 HM oscillator. A Type AC =l6Q
cable
is suitable for this
con-
nection.
This cable
is
not supplied
,
and may be procured from the
Hewlett
-
Packard Company
.
Model 416A Ratio Meter
-
Next the Model 416A is set up for operation.
3
1.
Plug the power
cable into a
power line of
specified voltage
and fre-
quency.
Turn the power
switch
to ON
.
Allow the
instrument
about
five
minutes to reach a state of
stable
operation.
2.
With
the
two BNC
-to-
BNC cables
furnished with
the Model 416A
,
con-
nect the detectors to
the
Model
416A inputs,
a
,
Connect the
incident
detector
to the
INCIDENT
/REFERENCE input.
b.
Connect the reflected (reverse) detector to the REFLECTED/
PROBE input.
3
.
Check the position
of
the EXCESS COUPLER LOSS switch. When a
20
-
db (Model X752D) coupler is used to sample the incident power
,
the switch should be set
at
10 DB
,
(At the
10 DB setting of the switch,
an
additional 10
db of
gain
is inserted
in
the incident channel.)
If
a
10-db (Model
X752C) coupler is used to sample
the
incident power
,
set
the EXCESS COUPLER LOSS switch at 0 DB,
4.
Connect the
OUTPUT /J3 connector
(Type BNC) on the rear of the
Model 416A
to the vertical input
of
a
d
~·
c
oscilloscope
.
5
.
Check
that the modulation
frequency on
and
level 3 of the
input
signal
voltage is within
operating
limits
.
I
nd
icati
on
that the
input signal i's
within frequency
and
voltage
limits
is
given by the
RF POWER MONITOR
(tuning eye)
.
Input filters in the Model 4 l
6A
are
sharply
tun
ed
to
1
,
000
cycles
.
Therefore
,
regardless of
input
signal
level
,
no
voltage will
reach
the
tuni
ng
eye
circuit
unl
ess
the
signal is within
±40 cycles of
1
,
000
cycles
.
However
,
when the input voltage
is of
correct frequency,
an input signal of even minimum level will cause the eye to
give
a
definite
indication
:
the shutter will
move
toward
closure
.
As
the
voltage of an
input signal of proper frequency
app
ro
aches
the
maximum level
,
the
eye closes completely
,
If
the eye
o verlaps by more than
1 /32
11
,
indication is given that the frequency of
the
voltage is correct
but
that
the
level
is too
h
i
gh
.
The reflectometer
system should
be operated
at
the lowest practical
input
power.
When the
input to the crystal detector
is
within
the
-
50 dbm
to
-
10 dbm
range,
the detector
is
operating largely
within its
linear region (Fig. 8
-
1),
and
output characteristics of
the
two
crystal detectors
will come
close
to tracking
.
A brief discussion
of crystal
detector
characteristics is given
under Possible
Error
If
Input
Power to Dete ctor Too High
,
below
.
-14-
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