Signal Hound USB-SA44B, Руководство пользователя, Страница: 10 / 18

Getting Started |
Limitations of the Signal Hound
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A traditional 1-3-10 RBW sequence is used by default in Spike, but any RBW up to 250 kHz may be
selected.
2.3.2 IF Feed-Through
Intermediate frequencies of 2.9 MHz and 10.7 MHz are used for all frequencies. An RF input signal near
these frequencies may generate spurious responses and degrade the performance of the image
rejection algorithm.
2.3.3 LO Leakage
A Local Oscillator signal may be observed at the RF input port, often found 10.7 MHz above the RF
frequency being scanned. Typically, this level will not interfere with your measurements. If you are
connecting to an antenna, set your reference level to -30 dBm to activate the preamplifier to minimize
LO leakage.
2.3.4 Sweep Time
Sweep Time may only be set in zero span mode. In all other modes, the minimum sweep time which
satisfies your RBW, VBW and span settings will be used.
2.3.5 Using an External Timebase
An external 10 MHz timebase my be used to improve the accuracy of frequency measurements. The
level of the external timebase must be > 0 dBm. +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,
then select external reference in the Spike
TM software.
2.3.6 Using Sync Out / Trigger In
A 3.3V CMOS output may be used to synchronize the USB-SA44B to the TG44A or TG124A tracking
generator. Legacy software allowed some additional triggering options available for a very limited range
of applications, but these have been removed to enhance the stability of our new platform. Consult the
appropriate manual for additional details.
2.3.7 Measuring Low Level Signals
To measure low-level signals, simply set your reference level to -40 dBm or lower. This internally selects
the highest sensitivity settings. Video averaging may be required for a stable amplitude reading.
2.3.8 Measurements near DANL
The amplitude displayed is the sum of all energy present in the IF. This includes the signal as well as
noise and residual responses. Measurements of signals less than 10 dB above the noise floor will have a
measurable amplitude error due to the addition of noise. To compensate for this, subtract the