Tektronix 2715, Руководство пользователя

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CATV Measurements
5–2
2715 User Manual
Be sure that the input power limitation is not exceeded before connecting a cable
feed to the RF INPUT. Read the information in Input Power Limitations below.
CAUTION.
To prevent damage, the safe maximum total RF input power for the
2715 is +70 dBmV. DC input voltage is limited to 100 VDC maximum.
Total input power above the rated maximum can cause damage to the instrument
and voids the factory warranty. For a number of equal amplitude signals, the
total power is approximately:
Total Signal = Single 10 log (Number of Signals)
Thus, the safe maximum amplitude per signal is given in Table 5–1.
Table 5–1: Safe Maximum Signal Levels
Number of Signals Input
to Spectrum Analyzer Safe Maximum Amplitude
per Signal (dBmV)
1
10
30
50
70
100
+70.0
+60.0
+55.2
+53.0
+51.5
+50.0
Remember, two 68 dBmV signals total more than 70 dBmV. Higher signal levels
should be externally attenuated.
With the exception of Adjacent Channel Leakage (ACL), these tests are
characterized for use in a multichannel environment (no preselector) or in a
single-channel environment (preselector used). ACL is characterized for the
single-channel environment only, since it is used only at the head end prior to the
system combiner.
In the multichannel environment, digital signals are typically 10 dB lower in
level than analog TV signals on the same system. In this case, the maximum safe
input level per channel may be unexpectedly far below the maximum safe total
power for the attenuator (+70 dBmV). For example, in a 150-channel flat system
dominated by analog TV signals, the maximum safe input level for a digital
signal 10 dB below the analog levels is only about +37 dBmV.
Input Power Limitations