Calibration—492/492P Service Vol. 1 (SN B030000 & up)
Performance Check
Fig. 3-13. Test equipment setup for measuring intermodulation distortion.
17. Check intermodulation Distortion (third order is
> —70 dBc from any two on-screen signals within any
frequency span. Option 01 from 1.8 to 18 GHz, IM is
> —70 dBc within any frequency span; and from 1.7
to 1.8 GHz, IM is s®—70 dBc down from any two
—40 dBm signals within any frequency span)
a. Set the front-panel controls as follows:
Vertical Display 10 dB/DIV
FREQUENCY RANGE Band 1
FREQ SPAN/DIV 5 MHz
RESOLUTION
BANDWIDTH 100 kHz
TIME/DIV AUTO
REF LEVEL -3 0 dBm
MIN RF ATTEN 0 dBm
MIN NOISE Off
Digital Storage (Option 02) VIEW A/VIEW B
d. Check third order intermodulation products (see Fig.
3-14). Ensure that third order products are -7 0 dB or more
down from the input signal level.
NOTE
Intermodulation products may not appear unless the
input signal level is offscreen. Use the VIDEO FILTER
and very slow sweep rates to help resolve these
sidebands.
Θ . Decrease signal separation and FREQ SPAN/DIV
settings and check again for sidebands. Check IM distortion
at other portions of the frequency range. IM distortion
should be down at least 70 dBc.
b. Apply two signals from two 50 Ω sources, separated
about 2 MHz and within the frequency range of band 1. Ap
ply the signals through 20 dB attenuators (for isolation), a
bnc *T* connector, and bnc-to-n adapter, to the 492/492P
RF INPUT (test equipment setup is shown in Fig. 3-13).
c. Adjust the output of the signal generators for two
-30 dBm, or full screen signals, on the 492/492P display.
Decrease the signal frequency separation to 1 MHz and the
FREQ SPAN/DIV to 500 kHz. Set the RESOLUTION
BANDWIDTH to 10 kHz.
Third (3rd) Order Intermodulation Products 2727-15
Fig. 3-14. intermodulation products.
3-28
REV AUG 1981
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