d. Adjust the DISPERSION CAL R208 (Fig. 6-22) for 1
marker/division over the center 8 graticule divisions, then
adjust C358 for display linearity.
e. Repeat the adjustment of R208 and C358 for optimum
dispersion accuracy and display linearity. If the dispersion
linearity is not within tolerance, a slight re-adjustment of
the RF Ampl R290 and the Center Freq Range R251 adjust-
ments may be required. Monitor the voltage at pin P of the
honeycomb square pin connector with the test oscilloscope
to keep the RF voltage amplitude within 0.75 to 1.0 volts and
recheck step 18.
22. Check Dispersion Accuracy of MHz/DIV
Ranges and Range of IF CENTER FREQ
Control
a. Test equipment setup is given in step 21.
b. Center the IF CENTER FREQ controls.
c. C h e c k t h e d i s p e r s i o n a c c u r a c y f o r e a c h M H z / D I V
setting of the DISPERSION selector as listed in Table 6-4.
The Horizontal POSITION central, or the IF CENTER FREQ
control may be used to align the prime markers to the
graticule divisions. As the DISPERSION is decreased, the
RESOLUTION control should remain in the coupled posi-
tion.
d. Check the range of the IF CENTER FREQ control plus
the dispersion accuracy and linearity over this range, in
the 5, 2, 1, .5 and .2 MHz positions of the DISPERSION selec-
tor.
Range of the coarse control should equal or exceed +
and - 25 MHz from its centered position. It is checked
by rotating the control to both extreme positions from cen-
ter and noting the frequency shift of the .1 s or 10 MHz
markers as the control is rotated. Dispersion accuracy and
display linearity must remain within the listed specifications
of Table 6-4 to the + and - 25 MHz positions.
e. Center the coarse IF CENTER FREQ control. Set the
DISPERSION control to 1 MHz position and apply 10 ns and
1 s markers from the Time-Mark Generator.
f. Check-The range of the IF CENTER FREQ-FINE con-
trol. Must equal or exceed + and - 1 MHz from its cen-
tered position.
6-22
