Performance Verification: AnalogS ection
4-12 WFM90D and WFM91D Service Manual
Chrominance Bandwidth
This procedureverifies the following requirement:
Chrominance Bandwidth: Upper --3 dB Point: FSC + 500 kHz, 100 kHz.
Lower --3 dB Point: FSC --500 kHz, 100 kHz.
1. Connect the precision 50 Ωcableto the output of the leveled sine wave
generator.Connect the other end of the cable to the 50 Ωto 75 Ωminimum-
loss attenuator,and then connect the attenuator to the VIDEO IN connector.
2. Select EXT REF from the Configuration menu.
3. Set the leveled sine wave generatorfrequency to 3.58 MHz (4.43 MHz PAL)
and adjust the amplitude control so that the circleoverlays the graticule
compass rose.
4. Decreasethe frequency on the leveled sine wave generator until the edge of
the circledisplay reaches t he --3dB (70%) gaps on th e vertical graticule axis.
See Figure 4--1.
Compassrose--3dB Points
Figure4 -1: -3 dB marks on the vector graticule
5. Check that the frequencyreadout on the leveled sine wave generator is
between 2.98 and 3.18 MHz (3.83 and4. 03 MHzPAL).
6. Adjust the frequencyon the leveledsine wave generator until the edge of the
circledisplay reaches the --3dB (70%) point gaps on the horizontal graticule
axis.
7. Check that the frequencyreadout on the leveled sine wave generator is
between 2.98 and 3.18 MHz (3.83 and4. 03 MHzPAL).