4-6.
EXTERNAL LEVELING
Specification
Table 4-11.
External Leveling Specifications
Description
The HP 8340B/41B external leveling circuit is designed to maintain a constant voltage at the EXT
INPUT BNC.
This is achieved by first selecting a voltage (in dBV) to which the EXT INPUT will be
leveled. This establishes a reference voltage for the ALC. The voltage at the EXT
INPUT
is then routed
through the external leveling circuitry to the ALC and compared to the reference. If a differnce
between the two voltages exist, the HP 8340B/41B RF OUTPUT power will be adjusted to compen-
sate for the difference.
The HP 8340B/41B’s external leveling circuit allows a positive or negative crystal detector to be used
in the external leveling loop. A negative crystal detector (HP 8473C) is used in this test but a crystal
detector may be substituted.
The HP 8340B/41 B XTAL Leveling mode is selected to verify the instrument’s external leveling specifi-
cation. Nine different dBV values, ranging from +6 dBV to —66 dBV, are selected and the voltage
accuracy at the
EXT INPUT
is checked with a
DVM.
HP
8340B/41B
UNDER TEST
lOOOpF
CAPAC I TOR
XTAL: Allows the HP 8340B/41B to be externally leveled by crystal detectors of positive or negative
polarity.
METER: Allows power meter leveling with any HP power meter.
Range (XTAL or METER): 500 microvolts (—66 dBV) to 2.0 volts (±6dBV)
Accuracy of voltage at EXT
INPUT
connector relative to the displayed level (leveling voltage is shown
in ENTRY DISPLAY in dBV): ±0.5dB
±
200 microvolts.
DIGITAL VOLTMETER
Figure 4-6.
External Leveling Test Setup
HP 8340B/41B
Performance Tests
4-33