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odel654A
Model 654A
Section V
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50 UNBAL
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REFERENCE
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SUPPLY
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I
SEE
FIGURE
5-
q :
L _________
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CONTROL
.
. .
.
.
.
.
.
I
..
.
XIK
....
+10,0
50 UNBAL
:s
extreme
)
that the
range
to
on
at both
for a meter
re5-J6and
nuation.
dication on
I be set to
osi
lion and
,I to return
,54A meter
Figure 5-16
.
Meter Tracking Adjustment
1.
Check the
654A
meter tracking
as
follows
:
I) Set the external attenuator to -ldB position
and adjust the 654A AMPLITUDE control
for
null indication on the dc null voltmeter; the
654A
meter should indicate 0 +/-0
.05dBm.
2) Set the
ex
ternal
a
ttenuator to 0 dB position
an
d
adjust
the 654A AMPLITUDE control for
null indication
on
the dc null
voltme
ter;
the
654A meter
should
indicate
-
I
±
0.0 I dBm.
3) I f the
tolerances
in
steps I) and 2) are not met
then
readjust A3R7
(Meter
Offset
Cal)
as
in
st
ep
c
and repeat
steps
d through i
of
this
paragraph .
j
.
The meter tracking adjustment is
completed
by
performing
Paragraph 5-60.
k.
For
troubleshooting informati on refer to Pa
ra-
graph
5-94.
5-60. AMPLITUDE
CONTROL
AND
METER
CALIBRATION.
-----------NOTE -----------
Perform adjustments
of
Paragraph 5-59
before
making the
following adjustments.
a. Connect the equipment shown in Figure 5-1 using
the
50
ohm
termination
.
b. Set the 654A controls as follo
ws:
FREQUENCY dial
.......
_ .
.
.
.
. __
_
. _ ..
....
1
FREQUENCY RANCE ..
. __
. __..
..
.....
XIK
OUTPUT LEVELdBm .
....
..
.
.
..
...
.
.
+ 10.0
IMPEDANCE ...
.
.
..
.
.
.
.........
. 50 UNBAL
c.
Adjust the
654A AMPLITUDE
control for an
indication
on
the
ac
differential voltmeter of
.7071 V rms (+ I OdBm); adjust A3 R7 (Meter Offset
Cal) for
a
654A meter indication
of
OdBm.
d. Set the
654A
AMPLITUDE control to the extreme
clockwise
position and
adjust
A3R20 (Amplitude
Cal)
for
an
ac
differential voltmeter indication of
O.SOV rms (approximately +11.05dBm)
.
e.
For troublesh ooting information refer to Para-
graph
5-95
.
5-61. AMPLITUDE ACCURACY CALIBRATION.
a.
Perform the Amplitude
Accuracy checks
of
Paragraphs 5-9 through 5-14 but
do
not make any
adjustments
except as outlined
below.
If the +/-1
%
limi
ts
are
met for
aU
impedances do
not
perform
the remaining
steps
of
this
Paragra ph
.
b. If th
e
+/-1
%
limits are not met for any
impedance:
I)
Verify
that
the
impedance
networks
on
the
Impedance Selector board (A4) have
th
e
correct impedance
and
if necessary replace any
faulty resistors. The impedance
can
be checked
by
meas uring
the
open
circuit
vo
l tage
(for
each
impedance)
which
should
be
twice
the
t e r minated
volta
ge
;
alternatively
set
the
allenuator
to -SOdB pOSition and measure the
output impedance with
an
ohmmeter.
2) Perform
procedure of
Paragraph 5-60 except, in
step c
(of 5-60)
adjust
the 654A AMPLITUDE
control
for
an
ac
different
ia
l
voltmeter
indication slightly
higher or lower than 0 .707V
rms (see
example
below) so
as
to correct any
error noted in
step
a of this Paragraph (5-61)
:
the
offset from
0.707V
rms
should be as
small
as
possible, but in
any case,
must
remain
within
the
limits
of 0.700 to 0.714V rms.
5-17
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