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3.
While manually sweeping the
Model 670HM'
oscillator
,
adjust the
ATTENUATION control on the
Model
670HM,
and
watch the
tuning
eye
on the
Mo
de
l
416A.
Adjust
the ATTENUATION control to obtain,
over the frequency
range,
an approxirnately 1
/8
11
gap in
the tuning
eye shutter.
4.
On the Model 670HM,
set the SELECTOR switch at
SWEEP.
5.
On the Model 416A:
a.
Set the RANGE
switch
at the 0 DB l 00%
position.
b.
Disconnect the cable from the REFLECTED /PROBE input con-
nector.
This sets up
a
con<lition of
zero
reflection.
6.
On the Oscilloscope:
a.
A horizontal
trace
should appear on the oscilloscope
.
The
osc
il-
loscope horizontal
-
sweep voltage is supplied
-from
the Model 670
Fl
M
and is synchronized with the frequencies being swept.
The oscil
-
loscope
vertical
amplifier is connected to the Model 41
6
A
,
and
under
a
zero
reflec
tion
conditi
on
there
will be
essentially zero
voltage on the vertical plates (actually a few tenths of a
volt).
,
b.
Adjust the horizontal amplifier
for d-c
ope ration
and
proper de
-
flection to position
the
hor
i
zontal trace
about
one
i
nch below center.
Usually
it
is necessary to adjust the vertical and horizontal
con-
trols.
Thus
the zero
reflection line
is established.
7.
On the Mode
l 416A:
a.
Reconnect the reflected detector cable to
the REFLECTED/PROBE
input connecto
r.
There is
a
short across the line, and therefore
there now exists
a
condition of
1
00%
reflection.
b.
Adjust the
SET TO FULL SCALE control
on the
Model
416A
to
ob
-
tain
an
indication
of
100%.
NOTE
: If
a l
00%
i
ndication cannot
be obtained, it indicates
that
there
i
s
a difference in
the
rectification efficiency
of
the
two
detectors
,
and
that the detector
with
the
l
ower
ef-
ficiency
i
s
in the reflected channel.
Therefore the two
detectors should
be reversed as
i
t
is desirable that the
detector
with the
g reater
efficie
n
cy
be
placed in the
re-
flected channel.
(If
the
differenc
e
in rectification efficiency
between
the
two detectors
is less than
6
db, sufficient gain
can be
inserted
by the
SET
TO FULL SCALE control
to
compensate for the
differe
nce.)
-1
6-
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