External Leveling - HP 8340B Manual

4-6. EXTERNAL LEVELING

Specification
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 (±6 dBV)
Accuracy of voltage at EXT INPUT connector relative to the displayed level (leveling voltage is shown
in ENTRY DISPLAY in dBV): ±0.5 dB
Description
The HP 8340B/41B external leveling circuit is designed to maintain a constant voltage at the EXT
This is achieved by first selecting a voltage (in dBV) to which the EXT INPUT will be
INPUT BNC.
leveled. This establishes a reference voltage for the ALC. The voltage at the EXT
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
HP 8340B/41B
UNDER TEST
HP 8340B/41B
Table 4-11. External Leveling Specifications
200 microvolts.
±
is checked with a
DVM.
DIGITAL VOLTMETER
Figure 4-6. External Leveling Test Setup
is then routed
INPUT
lOOOpF
CAPAC I TOR
Performance Tests 4-33