HP 4395A - Page 86

15. INPUT ATTENUATOR SWITCHING UNCERTAINTY TEST
(SA)
Description
This test measures the HP 4395A input attenuator switching uncertainty over the entire range
from 0 dB to 50 dB. The switching uncertainty is referenced to the 10 dB attenuator setting.
In this test, a 50.1 MHz CW signal is applied to the HP 4395A input through a step attenuator.
The signal amplitude is measured at each HP 4395A input attenuator setting. At each
measurement, the other measurement conditions are kept constant to measure the switching
uncertainty exclusively. The applied signal level is controlled using the step attenuator so as
to keep the signal level input to the rst mixer (the internal circuit stage following the input
attenuator) constant. For example, the step attenuator is decreased by 10 dB, when the
HP 4395A input attenuator is increased by 10 dB. The HP 4395A reference level is set to
the value of the input attenuator setting 0 40 dB. This keeps the HP 4395A internal IF gain
constant.
Specication
A input attenuator switching uncertainty
@0 dB to 30 dB, referenced to 10 dB ::: :::: ::::: :::: ::::: :::: ::::: :::: :::: ::::: ::::<
6 1.0 dB
@40 dB to 50 dB, referenced to 10 dB ::: ::::: :::: ::::: :::: ::::: :::: ::::: :::: ::::: ::<
6 1.5 dB
Test Equipment
Signal Generator ::::: :::: :::: ::::: :::: ::::: :::: ::::: :::: ::::: :::: ::::: :::: :::: ::::: :::
HP 8663A
Step Attenuator
1
, 10 dB step, VSWR  1.02 ::::: :::: ::::: :::: ::::
HP 8496G Opt. 001 and H60
Attenuator driver
2
:::: :::: ::::: :::: ::::: :::: ::::: :::: :::: ::::: :::: ::::: :::: ::::: :::: :
HP 11713A
Type-N Cable, 61 cm (two required) :::: :::: ::::: :::: ::::: ::::
HP 11500B or part of HP 11851B
BNC cable, 122 cm :::: ::::: :::: ::::: :::: ::::: :::: ::::: :::: :::: ::::: :::: ::::: :::: ::
PN 8120-1840
6 dB Fixed Attenuation, VSWR  1.015 (two required) :::: ::: HP 8491A Opt. 006 & Opt. H60
1: Calibration values for attenuation settings of 10 dB to 50 dB at 50 MHz are required.
Procedure
1. Record the step attenuator 50 MHz calibration values in the calculation sheet (\Calibration
Value" column).
2. Set the step attenuator to 40 dB.
3. On the signal generator, initialize the signal generator. Then set the controls as follows:
Controls Settings
Frequency 50.1 MHz
Amplitude +12 dBm
4. Connect the test equipment as shown in Figure 2-22.
Note
Connect the signal generator's 10 MHz frequency reference output to the
HP 4395A EXT REF Input on the rear panel as shown in Figure 2-22. With this
conguration, both the signal generator and the HP 4395A are phase locked to
the same reference frequency to obtain a stable measurement.
2-54 Performance Tests