For example, assume the output meter indicates
+
15 dbm,
the attenuator dials are set for 25 db,
the external resistive
load is 250 ohms, and the generator IMPEDANCE switch is
set at 150.
A,
To obtain the open circuit voltage of the generator:
1.
The reading of the output meter minus the attenu-
ator setting gives an output level of
-
10 dbm
(t15 dbm minus 25 db).
2.
The voltage at -10 dbm across the generator out-
put impedance (150 ohms) is
.
125 volts. Twice
.
125 volt is .25 volt, the open circuit voltage.
B.
Applying the formula:
EL
=
.25 x 250, or
.
156 volt
2.50
+
150
CAUTION
When using low output levels of -40 dbm or below (attenuator set
for
55
db or more), do not use the 600G position of the IMPED
-
ANCE switch
if
the accuracy of calibration of the output attenuator
is important.
If
it is desired to have
a
600-ohm single -ended out-
put at
a
low level,
use the 600 position of the IMPEDANCE switch,
and connect the lower OUTPUT binding post to ground via the
G
binding post.
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