Aeroflex 3901 - Page 235

Analog Duplex System
Subject to Export Control, see Cover Page for details.
8-29
AF SNR Hum & Noise
The AF SNR Hum & Noise reading measures the receiver of the radio under test. AF SNR
Hum & Noise is a measurement of the level of the audio signal that is demodulated by the
radio when the Test Set sends a modulated signal versus when the signal is not modulated.
To use the AF SNR Meter to obtain Hum & Noise measurements:
1. Connect the transmitter of the Test Set to the radio under test.
2. Connect the demodulated audio of the radio under test to on of the Test Set’s Audio In
Connectors.
3. Add modulation at the desired level to the Test Set.
4. Press the [Hum & Noise Ref Lock] Soft Key
to obtain a reference lock of the audio in the
signal received by the Test Set.
5. Remove the modulation from the Test Set’s transmitted signal.
6. The Test Set displays the AF SNR Hum & Noise measurement relative to the level of the
audio in the signal when the Test Set was being modulated.
[Hum & Noise Ref Lock] Soft Key
Sets a reference lock to the current Hum & Noise Meter reading. This soft key is only
available when Hum & Noise SNR is selected on the [SNR Meter] or [AF Meter] Soft Key.
[Gen Freq = Ana Freq + Dx Offset] Soft Key
Sets the RF Generator frequency to a value spaced from the RF Analyzer frequency as set in the
Dx Frequency Offset field on the Generators Tile
.
[INC/DEC] Soft Key
Opens a soft key sub-menu that increments or decrement a specific setting. These sub-menu
soft keys are:
[INC Gen Freq] / [DEC Gen Freq] Soft Key
Each press of the soft key causes the RF Generator frequency to increment or decrement by the
value set in the Freq Inc field on the Generators Tile
. This soft key is accessed by pressing the
[INC/DEC] Soft Key
.
[INC Gen Level] / [DEC Gen Level] Soft Key
Each press of the soft key causes the RF Generator level to increment or decrement by the value
set in the Level Inc field on the Generators Tile
. This soft key is accessed by pressing the [INC/
DEC] Soft Key.
[INC Ana Freq] / [DEC Ana Freq] Soft Key
Each press of the soft key causes the RF Analyzer frequency to increment or decrement by the
value set in the Freq Inc (Analyzer) field on the Analyzers Tile. This soft key is accessed by
pressing the [INC/DEC] Soft Key
.
[Return] Soft Key
Returns to the top level soft key functions for the Analyzers Tile.