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Page 4-46
GNS 400W Series Maintenance Manual
Rev. A
190-00356-05
Localizer Standard Signals
All RF input levels for the NAV receiver requirements are specified in dBm and do not require a
6 dB attenuator on the output of the signal generator provided the signal generator is calibrated
into a 50 ohm load.
Standard Test Signals
Unless otherwise specified, the RF input signals must be at a level of -53 dBm and have a
frequency within 0.001% of the assigned carrier frequency in addition to the characteristics
outlined below. Note: ddm (difference in depth of modulation) is the absolute difference in
percentage of modulation of two tones divided by 100.
Standard Localizer Test Signal
A standard localizer test signal is an RF carrier amplitude modulated simultaneously by 90 and
150 Hz tones so that the sum of their separate modulation levels is 40%
±
1%. The tones must
have the following characteristics:
They must be phase-locked in such a manner that their voltage waveforms simultaneously pass
through zero in the same direction.
The maximum simultaneous variation in frequency must not exceed ± 0.3%.
The total harmonic content of each tone must not exceed 3%.
The RF level must be -53 dBm and have a frequency within 0.001% of the assigned carrier
frequency unless otherwise specified.
Standard Localizer Centering Test Signal
A standard localizer centering test signal is a standard localizer test signal in which the difference
in depth of modulation of the 90 and 150 Hz signals is less than 0.001.
Standard Localizer Deviation Test Signal
A standard localizer deviation test signal is a standard localizer test signal in which the difference
in depth of modulation (ddm) of the 90 and 150 Hz signals is 0.093 ±0.002.
A NAV +LEFT output voltage of 90 millivolts results.
Standard Localizer Audio Test Signal
A standard localizer audio test signal is a standard localizer test signal to which is added a 1020
Hz signal amplitude modulating the carrier 30%.
Standard Audio Test Signal
A standard audio test signal is an RF carrier amplitude modulated 30% at 1020 Hz.
