7- 83
Operating Concepts
Knowing the Instrument Modes
• The frequency of the incoming signal should be within 0.5 to +5.0 MHz of the selected frequency or the
analyzer will not be able to phase lock to it.
CW Frequency Range in External Source Mode 300 kHz to 3 GHz (6 GHz for Option 006)
Compatible Sweep Types The external source mode will only function in CW time sweep. If the instrument
is in any other sweep type when external source is activated, the warning message CHANGED TO CW
TIME MODE will appear on the display.
External Source Requirements The external source mode has spectral purity and power input
requirements, which are described in the 8753ES and the 8753ET specifications and characteristics
chapters of the reference guide.
Capture Range In either automatic or manual mode, you can enter the frequency of the external CW signal
using the
softkey (located under the Stimulus key). The actual signal must be within
a certain frequency capture range as shown in Ta b le 7- 3 .
If the incoming signal is not within the capture range, the analyzer will not phase lock correctly.
Locking onto a signal with a frequency modulation component Although the analyzer may phase-lock
onto a signal that has FM, it may not accurately show the signal's amplitude. The accuracy of such
measurements depends greatly on the IF bandwidth you choose. Use the widest IF bandwidth available (3
kHz) if this problem occurs.
Tuned Receiver Mode
In the tuned receiver mode, the analyzer's receiver operates independently of any signal source. This mode
is not phase-locked and functions in all sweep types. The analyzer tunes the receiver to a synthesized CW
input signal at a precisely specified frequency. All phase lock routines are bypassed, increasing sweep
speed significantly. The external source must be synthesized, and must drive the analyzer's external
frequency reference. The analyzer's internal source frequency is not accurate, and the internal source
should not be used in the tuned receiver mode.
Using the analyzer's tuned receiver mode is useful for automated test applications where an external
synthesized source is available and applications where speed is important. Although the tuned receiver
mode can function in all sweep types, it is typically used in CW applications.
Typical test setup
1. Activate the tuned receiver mode by pressing
.
2. To perform a CW measurement using the tuned receiver mode, connect the equipment as shown in
Tab le 7-3 8753ET/ES External Source Capture Ranges
Mode CW Frequency Capture Range
Automatic 50 MHz
> 50 MHz
5 MHz of nominal CW frequency
10% of nominal CW frequency
Manual All 0.5 to +5 MHz of nominal CW frequency
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