LLZ 421
Operation and Maintenance Repair
ILS 420
6−61Ed. 01.10
SOAC
Procedure VAM−ILS: Line Input Calibration
Measuring equipment: Audio Generator, AF−Voltmeter (with true rms measurement)
The following procedure is to perform if the actually expected input level of the voice line connection
requires a different gain than the default setting of 10 dB.
If the expected input signal level requires more than 10 dB gain (up to 70 dB gain achievable), perform
the following procedure:
− Connect an audio generator to the line input.
− Set switch S1 to lower position.
− Set jumper X23 to disable compression; adjust R8 and R9 to their rightmost position.
− Set the audio generator level such, that at X32 the maximum expected level is measured.
− Measure the level at X18 and turn R8 left to get approx. 220 mV
rms
. If the 220 mV
rms
is not achieved,
the remaining gain is set at pre−amplifier 1: close X30 and adjust with R4 to 220 mV
rms
.
− Measure the level at X18 and turn R9 left to get approx. 700 mV
rms
(approx. 10 dB gain).
− Measure the level at PI17 and adjust with R2 to 3.75 mV
rms
.
− Measure the level at PI16 and adjust with R3 to 3.75 mV
rms
.
− Open jumper X23 to enable compression.
If less than 10 dB gain is required, perform the following procedure:
− Connect an audio generator to the line input.
− Set switch S1 to lower position.
− Set jumper X23 to disable compression; adjust R8 and R9 to their rightmost position.
− Set the audio generator level such, that at X32 the maximum expected level is measured
− Measure the level at X18 and turn R9 left to get approx. 700 mV
rms
.
− Measure the level at PI17 and adjust with R2 to 3.75 mV
rms
.
− Measure the level at PI16 and adjust with R3 to 3.75 mV
rms
.
− Open jumper X23 to enable compression.
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