Tektronix WFM90, WFM91 - page 70

Performance Verification
4–12 WFM 90 and WFM 91 Service Manual
3. Set the leveled sine wave generator frequency to 3.58 MHz (4.43 MHz PAL)
and adjust the amplitude control so that the circle overlays the graticule
compass rose.
4. Decrease the frequency on the leveled sine wave generator until the edge of
the circle display reaches the –3 dB (70%) gaps on the vertical graticule axis.
See Figure 4–1.
Compassrose–3 dB Points
Figure 4–1: –3 dB marks on the vector graticule
5. Check that the frequency readout on the leveled sine wave generator is
between 2.98 and 3.18 MHz (3.83 and 4.03 MHz PAL).
6. Adjust the frequency on the leveled sine wave generator until the edge of the
circle display reaches the –3 dB (70%) point gaps on the horizontal graticule
axis.
7. Check that the frequency readout on the leveled sine wave generator is
between 2.98 and 3.18 MHz (3.83 and 4.03 MHz PAL).
8. Increase the frequency on the leveled sine wave generator until the edge of
the circle display expands out to the compass rose and again reduces to the
–3 dB (70%) point gaps on the vertical graticule axis. See Figure 4–1.
9. Check that the frequency readout on the leveled sine wave generator is
between 3.98 and 4.18 MHz (4.83 and 5.03 MHz PAL).
10. Adjust the frequency on the leveled sine wave generator until the edge of the
circle display reaches the –3 dB (70%) point gaps on the horizontal graticule
axis.