Field Audit Of Performance - Orban OPTIMOD-FM 8500S Operating Manual

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MAINTENANCE

Field Audit of Performance

Required Equipment:
•
Ultra-low distortion sine-wave oscillator/THD analyzer/audio voltmeter
With verified residual distortion below 0.01%. Audio Precision System
One, or similar high-performance system.
The NAB Broadcast and Audio System Test CD is an excellent source of
test signals when used with a high-quality CD player.
•
Spectrum analyzer with tracking generator
Stanford Research Systems SR760 or equivalent. Alternatively, a sweep
generator with 50-15,000 Hz logarithmic sweep can be used with an os-
cilloscope in X/Y mode, or you can use a computer-controlled test set like
the Audio Precision System Two.
•
Digital voltmeter
Accurate to ±0.1%.
•
Oscilloscope
DC-coupled, triggered sweep, X/Y display-capable with 10 MHz or
greater vertical bandwidth.
•
Optional: Audio Precision System 1 (without digital option) or System 2 (for digi-
tal tests).
•
Optional: NTI Audio Digilyzer DL1 for digital output tests
•
Optional: Synthesized 10 MHz function generator for sync tests
Stanford Research Systems DS340 or equivalent.
The technician should be thoroughly familiar with the operation of this equipment.
This procedure is useful for detecting and diagnosing problems with the 8500S's per-
formance. It includes checks of frequency response, noise and distortion perform-
ance, and output level capability.
This performance audit assesses the performance of the analog-to-digital and digi-
tal-to-analog converters and verifies that the digital signal processing section (DSP)
is passing signal correctly. Ordinarily, there is a high probability that the DSP is per-
forming the dynamic signal processing correctly. There is therefore no need to meas-
ure such things as attack and release times — these are defined by software and will
automatically be correct if the DSP is otherwise operating normally.
It is often more convenient to make measurements on the bench away from high RF
fields which could affect results. For example, in a high RF field it is very difficult to
accurately measure the very low THD produced by a properly operating 8500S at
most frequencies. However, in an emergency it is usually possible to detect many of
ORBAN MODEL 8500S