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1 0 dB/
NEG PK
CENTER
Figure 3. Video Bandwidth Step Display with Negative Peak Detection
If the displayed noise does not change monotonically ( continuously decrease level) with the
step key, the indicated Video bandwidth is faulty. Refer to the service sheet to determine the
defective switch, capacitor, or decoder.
The Log Expand and Decode Logic circuitry can be accurately checked by using the Error
Correction Routine. Pressing
terms are displayed by pressing CSHIFT) (LINE] (KSw). The last three lines give the offset errors
from the 1 dB LOG reference for the 2 dB, 5 dB, 5 dB, and 10 dB LOG scales, respectively.
Maximum error is 410.5 dB for proper operation.
R E F - 9 0 . 0 d5-n
7
2 5 . 0 0 0 M H z
RES BW 1 kHz
V B W 3 0 kHz
FREQUENCY SPAN
I
1
S P A N 1 0 0 kHz
(KSW) starts this routine. The error
)
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