Tektronix 1705A - page 118

Checks and Adjustments
1705A Spectrum Monitor 5-23
i. Repeat part i. using 2 dB/Div if necessary.
j. ADJUST --C69 for maximum signal.
k. ADJUST--L4 for maximum signal. (The slug may beremoved if L4
provides no benefit.)
l. Repeat this step asnecessary until the signal amplitude is 37 to 43 dB
above the noise floor.
9. AdjustRamp Size
a. On the 1705A select70 MHz INPUT, turn the CENTER FREQUENCY
knob fully counterclockwise,and set the SPAN/DIV to 1 MHz.
b. Set the DVM to AC Volts.
c. Connect the ground leadto chassis ground and the active lead to W5.
SeeFigure5-7.
d. Note readingon the DVM (should be ¶0.4 volts).
e. Connect the DVM to W2. See Figure 5-7.
f. Set the 1705A SPAN/DIVto FULL.
g. ADJUST--R113 (FULL GAIN) to match the reading from part d.
10. Adjust 70 MHz Band Linearity
a. Set SWEEP SPEED fully clockwise, SPAN/DIVto 1 MHz, and adjust
the HORIZONTALPOSITION to place the caret on the center graticule.
b. Set the SPAN/DIVto FULL.
c. Connect the signal generatoroutput to the 1705A 70 MHz INPUT.
d. Set the signal generatorFrequency to 45 MHz, and the Amplitude to
--25 dBm.
e. ADJUST-- R55 to place the signal on th e extreme left graticule.
NOTE. Ramp start amplitude (step 9)should be verified after R55 and 70 MHz
linearity arecompleted and the 70 MHz tuner cover is on. All of these adjust-
ments interact and ramp start amplitudeis critical for proper linearity.
f. Connect the signal generatoroutput to the 1705A 70 MHz INPUT
through the comb generator.