Tait T830 Series, Руководство по обслуживанию

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31/01/96 Copyright TEL
4.4 Audio Distortion
The level of distortion measured at the line output gives a good indication of the accu-
racy of the IF alignment.
Apply an accurate on-channel signal from the RF generator at a level of -70dBm
with 3kHz deviation [1.5kHz] at 1kHz.
Adjust the front panel line level control (RV102) to give +10dBm into 600 ohms.
Check that the distortion is approximately 1% THD.
Note: For a de-emphasised response, the distortion should always be better than
2% for wide band sets or 4% for narrow band sets.
Adjust the front panel monitor volume control (RV103) to give 2V rms into a 4
ohm resistive load.
Check that the distortion at the monitor output is better than 2% THD.
4.5 Ultimate Signal-To-Noise Ratio
Apply a signal from the RF generator at a level of -57dBm with 3kHz deviation
[1.5kHz] at 1kHz.
Select de-emphasis on the links provided in the audio processor (refer to Section
3.3), and link pins 2 & 3 of PL105 to include the 300Hz filter.
Adjust RV102 (line level) to p10dBm output.
Switch off the modulation, checking that the residual noise is lower than -45dBm
[-39dBm] at the line output (this corresponds to S/N of 55dB [49dB] and is in
accordance with EIA measurement conditions).
Note: The measurement can be made without the 300Hz high pass filter but will
give a result which is 10dB worse.