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A D D I T I O N A L
F E A T U R E S
4.1.3
Listening to Demodulated Audio
When you identify a modulated signal and wish to listen
to the modulation, you may position your marker on the
signal in question and select Utilities
the CENTER FREQ will be used. This frequency will be pre-loaded into the dialog
box on the left. Additional demodulation options will be preloaded with the last values
used or default settings.
Please have span set to 200 KHz or less before entering Audio Listen mode to ensure
device is set up correctly and on frequency.
Frequency represents the center frequency of the RF carrier.
⇒
Modulation Mode may be set to AM, FM, SSB (upper or lower sideband) or
⇒
CW.
IF Bandwidth may be set from 30 KHz to 240 KHz.
⇒
FM De-emphasis is a digital single pole low-pass filter, used to remove the high-
⇒
frequency emphasis used in many FM broadcasts or to filter out noise.
Apply Changes stops the demodulation, applies any new settings, then re-starts
⇒
the audio.
4.1.4
Using an External Timebase
An external 10 MHz timebase my be used to improve the accuracy of frequency and
phase noise measurements.
+13 dBm is recommended to achieve optimal phase noise performance. To use,
simply connect the timebase to the Ext Ref In after connecting the USB, launch the
software, then select Utilities External Reference.
4.1.5
Using an External Trigger
A TTL/CMOS trigger may be used to initiate a sweep at a specific time. The trigger
must be a 3.3V or 5V TTL/CMOS. To activate, select
Settings SYNC/TRIG TRIG IN. The selected sweep will wait for a trigger, then
begin within 10 microseconds of the trigger's rising edge. When using an external
trigger, remember that image rejection happens in a separate sweep, after the first
sweep is triggered, so turn it off if it will interfere. If you are trying to capture an
event, you may wish to use Zero Span (AM or FM).
Audio Listen. If you do not place a marker,
The level of the external timebase must be > 0 dBm.
25
Figure 4: Audio Listen
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