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TYPE 1263-B AMPLITUDE-REGULATING POWER SUPPLY
RELATIVE
AMPLITUDE
MODULATION
0 db=
100% A.M.
-10
-20
-30
I
IMPEDANCE AT BLANKING
TERMINALS • 5000 ohms
AT I VOLT R-F LEVEL
{DIRECTLY
PROPORTIONAL
1-.
~AM
ITI
~
LEVELl
.;;;;;;::::
NOTES:
~
CURVE REPRESENTS OVERLOAD
I'.
30%A.M.
LIMITATION, NOT FREQUENCY
~--~--
CHARACTERISTIC OF RESPONSE.
RESPONSE IS FLAT FOR All
~ ~~2~LCI~~~s v~~::EES~N;~~S
BY CURVE.
~%A.M.
FOR R-F OUTPUT LEVELS
LESS
THAN
I VOLT THE LIMITING
MODULATION
. . . . . . . . . . . . . . !--
VOLTAGES ARE PROPORTIONALLY SMALLER.
~
I VOLT R-F OUTPUT SHOULD NOT BE
EXCEEDED
UNDER MODULATION
OR
OTHiR
LliiTAIIOis
1
ii!Lr
iPPEAR.
1
I
10
100
1000
MODULATING
FREQUENCY IN CYCLES PER SECOND
MAXIMUM
p ERMIS SIBLE
MODULATING
VOLTAGE
O.Bv
0.4v
0.2v
O.lv
0.051/
0.02511
ACROSS
BLANKING
TERMINAL
WITH I VOLT
R-F LEVEL
10,000
Figure 5. Typical external amplitude-modulation characteristics
of the Type 1263-B
produces the maximum modulation that can be obtained without spoiling
the output regulation.
Connect a blocking capacitor
in
series with the
lead to the high (red) BLANKING terminal, and set the output voltage to
1 volt. At a 1-volt output, the input impedance is about 5000 ohms, and
a 20- f.1 f blocking capacitor is suitable at frequencies above 20 cps. If
the blocking capacitor is an electrolytic, connect its negative terminal
to the high (red) BLANKING terminal.
At outputs smaller than 1 volt,
the voltmeter diode nonlinearity causes greater modulation nonlinearity
and lower
input
impedance.
Therefore,
it
is recommended that
if
lower
outputs are desired, the required attenuation be added at the output of
the Type 874-VR.
If necessary, equip the modulating source with a voltage divider to
limit
the voltage available to about 1 volt, so that the modulating voltage
may more easily be set to the required value.
13
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