Tektronix 1705A - Manual (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 be removed if L4
provides no benefit.)
l. Repeat this step as necessary until the signal amplitude is 37 to 43 dB
above the noise floor.
9. Adjust Ramp Size
a. On the 1705A select 70 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 lead to chassis ground and the active lead to W5.
See Figure 5-7.
d. Note reading on the DVM (should be
¶0.4 volts).
e. Connect the DVM to W2. See Figure 5-7.
f. Set the 1705A SPAN/DIV to 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/DIV to 1 MHz, and adjust
the HORIZONTAL POSITION to place the caret on the center graticule.
b. Set the SPAN/DIV to FULL.
c. Connect the signal generator output to the 1705A 70 MHz INPUT.
d. Set the signal generator Frequency to 45 MHz, and the Amplitude to
--25 dBm.
e. ADJUST -- R55 to place the signal on the extreme left graticule.
NOTE. Ramp start amplitude (step 9) should be verified after R55 and 70 MHz
linearity are completed and the 70 MHz tuner cover is on. All of these adjust-
ments interact and ramp start amplitude is critical for proper linearity.
f. Connect the signal generator output to the 1705A 70 MHz INPUT
through the comb generator.