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GNS 400W Series Maintenance Manual
Page 4-53
190-00356-05
Rev. A
4.7
GLIDESLOPE RECEIVER TESTS
Standard Loads
Glideslope Receiver Antenna
The glideslope receiver antenna must operate in a 50 ohm load.
Course Deviation Deflection Load
One standard CDI deflection is 1000 ohms.
Course Deviation Flag Load
One standard CDI flag load is 1000 ohms.
To/From Load
One standard TO/FROM load is 200 ohms.
Standard Signals
All RF input levels for the glideslope 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 Glideslope Test Signal
•
A standard glideslope 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 80% ± 2%.
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 -56 dBm and have a frequency within 0.001% of the assigned
carrier frequency unless otherwise specified.
Standard Glideslope Centering Test Signal
A standard glideslope centering test signal is a standard glideslope test signal in which the
difference in depth of modulation of the 90 and 150 Hz signals is less than 0.002 ddm.
Standard Glideslope Deviation Test Signal
A standard glideslope deviation test signal is a standard glideslope test signal in which the
difference in depth of modulation of the 90 and 150 Hz signals is 0.091 ± 0.002 ddm.
