Section III
TM 11-6625-2781-14&P-2
INPUT POWER AND
12. Readjust VERTICAL POSITION until trace
INTENSITY MODULATION
aligns with bottom line of graticule.
1. Set 115/230 switch to correspond with available
VERTICAL POSITION AND GAIN
input voltage. (The instrument is fused for 115-
13. Connect CAL OUTPUT (30 MHz/-30 dBm)
volt, 50/60 Hz operation; if 230-volt power is
signal to RF INPUT; select 0-100 SCAN
used, refer to the display section service manual
WIDTH.
for fuse replacement procedures.)
14. Tune FREQUENCY until negative marker
2. Set INT/EXT switch to INT. (Set to EXT only if
causes maximum dip in signal that appears on
CRT is to be externally modulated - normally
"-2" vertical line of graticule (30 MHz) red
used with 1400-series time-domain plug-ins.)
marker on CENTER FREQUENCY MHz scale
3. Connect 8553B Load Assembly A14.
should be pointing at 30.
FOCUS AND ASTIGMATISM ADJUSTMENTS
15. Set:
4. Set:
SCAN WIDTH (inner/red) to PER DIVISION
POWER ON (up observe that ON lamp lights)
SCAN WIDTH (outer/black) to 0.2 kHz
BASE LINE CLIPPER, fully ccw
BANDWIDTH to 300 kHz LOG-LINEAR to LOG
SCAN WIDTH (inner/red) to ZERO
INPUT ATTENUATION to 10 dB
INPUT ATTENUATION to 10 dB
LOG REF LEVEL: -30 dBm graduation to
BANDWIDTH to .3 kHz
match lighted index lamp and vernier set to 0
SCAN TIME PER DIVISION to 10 SECONDS
16. Fine-tune for max. amplitude of signal.
SCAN MODE to INT SCAN TRIGGER to AUTO
17. Rotate AMPL CAL until trace is centered on top
LOG REF LEVEL controls: -20 dBm graduation
line of graticule at the CENTER FREQUENCY
matching lighted index lamp and vernier set to 0
position.
INTENSITY clockwise until trace is medium
18. Rotate LOG REF LEVEL counterclockwise and
bright (approx. 1 o'clock position).
note that the signal decreases one division (10
dB) for each calibrated switch position. If trace
RANGE-MHz to 0-110
moves one division per step in lower part of
5. Adjust FOCUS and ASTIGMATISM controls
graticule but the amplitude creeps upward near
until combined effect produces best resolution
top of graticule, adjust VERTICAL GAIN until
(maximum roundness without fuzz) of the dot.
each step is equal.
TRACE ALIGNMENT
LINEAR AND LOGARITHMIC ADJUSTMENT
6. Set SCAN TIME PER DIVISION to 5
19. Rotate LOG REF LEVEL control until signal
MILLISECONDS.
trace appears on fourth graticule line from
7. If not already aligned, adjust TRACE ALIGN
bottom.
until trace is aligned with horizontal line of
20. Set LOG/LINEAR switch to LINEAR and rotate
graticule. HORIZONTAL POSITION AND GAIN
LOG REF LEVEL control until 1 mV/DIV is
8. For convenience in making these adjustments,
matched with the lighted index lamp.
move trace to upper half of graticule by
21. Reading from bottom of graticule (LIN scale),
adjusting the VERTICAL POSITION control.
signal amplitude should be 7.07 millivolts. If it
9. Rotate HORIZONTAL GAIN until trace is of
is not, repeat vertical position and gain
minimum length.
adjustments until proper reading is obtained.
10. Rotate HORIZONTAL POSITION until trace is
22. Rotate LOG REF LEVEL control until -30 dBm
centered on CENTER FREQUENCY line of
graduation matches the lighted index lamp. Set
graticule.
LOG/LINEAR switch to LOG. Signal trace
11. Alternately
adjust
HORIZONTAL
should align with top (LOG REF) line of the
POSITION/GAIN controls until trace begins at
graticule.
first line of graticule and ends at last.
Figure 3-2. Operational Adjustments
3-6
