IFR COM-120B - Page 31

Rev. 1.0 Page 31
SINAD =
Signal + Noise + Distortion
Noise + Distortion
The COM-120B has been
configured with the
AUDIO/DATA Input routed
to the scope to view the
radio’s demod output. This
is the same signal that the
SINAD meter will evaluate.
The COM-120B injects a
carrier modulated with a 1
kHz tone at 3.3 kHz
deviation into the radio’s
reciever.
4. Position the cursor to the Level field. [TAB] [4] [ENTER]
5. Press the [ENTER] key to highlight the RF Level value and adjust
with the Knob control to reduce the level until the COM-120B’s
SINAD meter indicates approximately 12 dB. Note: The monitor
button on the radio may need to be held down to defeat the radio’s
squelch operation.
RF Signal
Generator
Receiver
Under Test
Audio
Filter
R.M.S.
Voltmeter
R.M.S.
Voltmeter
Notch Filter
Audio Output
Notch Filter removes 1 kHz tone
1 kHz Tone + Noise + Distortion products