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4.2.10 Stopband Attenuation
NOTE:
This test uses a spectrum analyzer to detect the rejected signal. Most spectrum analyzers have a
maximum signal amplitude without damage limit. Care should be taken that this signal level limit is not
exceeded. A simple precaution would be to use a 50 ohm in line 20dB attenuator at the analyzer input. It is
also advisable to set all the equipment before connecting the analyzer.
Set the filter to the initial settings at the beginning of this section.
Set the filter coupling to AC, cutoff frequency to 10kHz and mode to gain.
Set the Tektronix 191 signal generator for 1MHz, 3Vp-p into 50 ohms.
Connect the Tektronix 191 to the filter input.
Set the spectrum analyzer to measure the 3Vp-p, 1MHz signal into a 50 ohm termination at the filter output
and connect ther filter output to the analyzer.
Adjust the analyzer for 0dB, referencing level at the 1MHz signal.
Set the filter for Low-Pass mode.
The measured amount of 1MHz signal should be down 100dB.
Set the signal generator for 10MHz.
The measured amount of 10MHz signal should be down 80dB.
Set the signal generator for 30MHz.
The measured amount of 10MHz signal should be down 70dB.
NOTE:
Zero referencing of the spectrum analyzer at 100MHz must be done by connecting the signal gen-
erator to the spectrum analyzer input.
Set the signal generator for 100Mhz.
The measured amount of 100MHz signal should be down 50dB.
End of Procedure.
Section 4 - Incoming Acceptance
4-8
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