Maintenance Manual

Table Of Contents

This field sets the main LF input channels sensitivity, i.e. multiplex, left and right channel. Note that

the multiplex and right channel share the same circuitry and the sensitivity is set to the same value

for all audio /multiplex channels, with a differential error (<0.2dB) at any level. Adjustment range is

- 3.5 -

+12.5 dBm.

The upper line of the display shows the modulation corresponding to the LF signal currently present,

while the bottom line shows the nominal input level for 100% modulation, (75kHz). Increasing the

nominal input level consequently reduces the modulation, if the modulating signal remains constant.

• Field #25: Auxiliary Input Level setup

AUX 2.0kHz -31.5dB

Nom.input = + 0.0dBm

This field adjusts the auxiliary channels input sensitivity. Adjustment range is -12 - +4 dBm to

produce 10% modulation, corresponding to the deviation of 7.5kHz or -20dB in the upper line of the

display. On this line the actual modulation of the channel is shown in real time. On the lower one the

nominal value of the sensitivity in dBm, the parameter on which we act in this screen.

• Field #26: Limiter setup

MPX Limiter + 7.1dB

This field sets the limiter action. Threshold level and enable / disable can be adjusted separately. The

limiter may be set to the maximum allowed modulation level for 75kHz-peak deviation, (0dB), so that

the transmitter prevents signals which would exceed this value, or if regulations allow, the limiting

value may be slightly higher to provide some dynamic headroom for some occasional modulation

peaks

It is recommended, not to frequently exceed the limiter threshold with modulation peaks.

Repeatedly exceeding the threshold can cause a heavy audible distortion.

Conversely, setting the threshold to high above the corresponding deviation level would be no

difference with the limiter on or off