Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-22. RESIDUAL FM TEST (Cont'd)
8. Remove the capacitor and replace 3 kHz LPF with 15 kHz LI'F. The average( voltmeter reading should be less
than 15 mVrms (i.e., <30 Hz (rms) residual FM).
-------------------15 mVrms
4-23. OUTPUT LEVEL ACCURACY TEST (Abbreviated)
SPECIFICATION:
Range: 10 dB steps and 18 dB vernier provide output power settings from +19 to -145 dBm (2V to 0.013 µ V) into 50
Ω
.
Level Accuracy:
Using Full
Using Top 10 dB of Vernier Range
Vernier Range
Output Level (dBm)
+19 to -7
-7 to -47
-47 to -137
+19 to -145
Total Accuracy as
Indicated on
1.5 dB
+2.0 dB
+2.5 dB
Add +0.5 dB
Level Meter
DESCRIPTION:
The RF level accuracy for the upper four OUTPUT LEVEL attenuator ranges is measured with a power meter. For the
lower ranges, a reference signal is established on a spectrum analyzer display, the Signal Generator's OUTPUT LEVEL
switch and the spectrum analyzer's vertical scale log reference level control are stepped together, and any amplitude
variations are measured on the analyzer's display. An RF attenuator and amplifier at the RF OUTPUT are adjusted for
analyzer compatibility and best sensitivity.
This procedure uses an IF substitution technique in which the spectrum analyzer's IF is the standard. The IF step
accuracy should be within ± 0.2 dB overall. The IF step accuracy can be checked using the above technique by
comparing a lab calibrated attenuator (such as HP Model 355D Option 1136) with the IF step control at the frequency of
attenuator calibration (e.g., 3 MHz for the HP 355D Option H36).
NOTE
This procedure checks output level accuracy from +19 dBm to -127 dBm, all of the attenuator
sections in the OUTPUT LEVEL step attenuator, and the OUTPUT LEVEL vernier. If, in addition,
level accuracy must be verified down to 145 dBm, see paragraph ,4-24.
4-24
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