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GNS 400W Series Maintenance Manual
Page 4-47
190-00356-05
Rev. A
4.6.3 NAV
Receiver
Voice/Ident Audio Output Level
1.
Apply a standard audio test signal having a RF level of -93 dBm.
2.
Select maximum audio (volume control turned fully clockwise).
3.
Turn off the ident filter.
4.
Measure 500
Ω
VOR/ILS AUDIO HI J6-16 with respect to 500
Ω
VOR/ILS AUDIO LO
J6-17.
5.
Verify an audio output level into a 500 ohm load that is not less than 20 Vpp (7.07
Vrms).
6.
Select minimum audio (volume control turned fully counter clockwise without turning
off). Verify that an audio output level into a 500 ohm load is not more than 63 mVpp
(22 mVrms).
Voice/Ident Audio Frequency Response
With the IDENT mode selected, the difference between the maximum and minimum
VOICE/IDENT audio output levels measured at the NAV AUDIO HI output for 350 Hz and 2500
Hz relative to the frequency of max output must be less than 6 dB, when the RF input level is -73
dBm.
With the IDENT mode selected, the difference between the maximum and minimum
VOICE/IDENT audio output levels measured at the NAV AUDIO HI output for 150 Hz relative
to the frequency of max output, and for 9000 Hz relative to the frequency of max output must be
not be less than 20 dB, when the RF input level is -73 dBm.
•
Measure NAV AUDIO HI J6-16 with respect to NAV AUDIO LO J6-17 and verify that
the above requirements are met.
Voice/Ident Audio Distortion
This test is measured at NAV AUDIO HI J6-16 with respect to NAV AUDIO LO J6-17. Use -79
dBm for this test since distortion at lower RF level is higher.
Verify the following:
The combined distortion and noise in the receiver VOICE/IDENT audio output must not exceed
10% at all levels up to 100 mW. This requirement must be met over the RF input range of -79 to
-27 dBm using a standard VOR audio test signal at modulation frequencies of 350 Hz, 1000 Hz,
and 2500 Hz.
VOR AGC
Measure NAV AUDIO HI J6-16 with respect to NAV AUDIO LO (GND) J6-17. Must be in
IDENT mode to pass 1000 Hz tone.