Operating instructions

OPERATING MANUAL 2945A
46882-311D 3-23
Audio distortion measurement
The Service Monitor is able to measure signal noise and distortion against the following
parameters:-
Signal to noise
ratio
SINAD
level
Percentage
distortion
Press the [Dist S/N] key. The right hand soft keys change, to allow selection of S/N, SINAD and
distortion measurements.
Off
Disables any active distortion measuring function.
Hint.
By disabling this function, the time taken to measure the remainder of the measurement functions
is shortened thereby reducing the update time.
S/N
Selects signal to noise ratio as the measurement method. The Signal to Noise bar chart ranges
available are 0 to 30 dB and 0 to 100 dB. The signal to noise ratio is displayed as a digital
read-out above the bar chart. The TX TEST mode menu is recalled automatically after pressing
this key.
SINAD
Selects SINAD as the measurement method.
The AF1 generator will be set to 1 kHz by this action, regardless of any previous setting.
The distortion bar chart ranges available are 0 to 18 dB and 0 to 50 dB. The SINAD level is
displayed as a digital readout above the bar chart. The TX TEST mode menu is recalled
automatically after pressing this key.
Dist’n
Selects distortion percentage as the measurement method.
The AF1 generator will be set to 1 kHz by this action, regardless of any previous setting.
The distortion bar chart ranges available are 0 to 10%, 0 to 30% and 0 to 100%. The distortion
percentage level is displayed as a digital readout above the bar chart. The TX TEST mode menu
is recalled automatically after pressing this key.
With all the required parameters set, power up the transmitter.
The power output of the transmitter is shown on the POWER LEVEL bar chart, with the power
level given in digital form above it.
The level of modulation is displayed on the modulation level bar chart, with the FM DEVN or the
AM DEPTH shown digitally. When the SSB demodulation function has been selected, no
modulation bar chart is displayed. The legend ‘SSB Trans’ and the selected sensitivity is shown.
The FREQ OFFSET will indicate the difference between the mean (measured) frequency of the
transmission and that entered as transmitter frequency.