Section III Models 691A/692A/693A/694A
Paragraphs 3-52 to 3-70
3-52. During a triggered sweep Oscillator output frequency of the selected sweep. Counterclockwise
frequency changes linearly with time, and SWEEP ON rotation varies output frequency toward the sweep
is lighted. start frequency. The SWEEP ON light does not func-
tion with manual sweeping.
3- 53. Externally-produced trigger signals must have
negative polarity, width greater than 1 psec and rise 3-61. Manual sweep is particularly useful for cali-
time of at least 0.1 volt/psec. Less than 25 volts bration of a display device such as an oscilloscope
or graphic recorder prior to automatic swept-fre-
amplitude will trigger a sweep. During slow sweeps quency measurements. Its use in this zyplication is
a sweep can be interrupted and reset by pressing the described in more detail under Displaying Swept-
MANUAL pushbutton. Frequency Measurements.
3-54. Three sweep-synchronized outputs are acti-
vated during TRIG operation: SWEEP, SWEEP REF 3-62. THE SWEEP TIME CONTROL.
and PENLIFT. In addition, the Oscillator RF output 3-63. The sweep time control consists of a four-po-
is automatically turned off, or blanked between sition range selector and a vernier for continuous ad-
sweeps if the rear-panel BLANKING and ALC PWR
LEVELING INPUTS switches are at ON and XTAL, justment of sweeping time within the limits of each
respectively. time range. Clockwise rotation of the vernier de-
creases sweeping time, the clockwise rotation limit
giving the minimum time, and the counterclockwise
3-55. cw. limit giving the maximum time of the range selected.
3-56. The CW mode gives single-frequency operation The detent LINE SYNC position of the vernier synchro-
and may be used with either the start-stop or marker nizes sweeping with the power line frequency, but
sweep functions. Output frequency can be set any- restricts sweeping time to the minimum of the range
where in the Oscillator frequency range. Obtain CW selected.
output as follows:
3-64. The sweep time controls are operational with
a. Set LINE to RF. start-stop, AF, and marker sweeps in the AUTO and
TRIG modes. However, LINE SYNC does not function
b. Set SWEEP SELECTOR to CW. with triggered sweeps.
c. Press START-STOP or MARKER SWEEP.
d. Tune to desired frequency using START/CW or 3-65. THE SWEEP OUTPUT.
MARKER 1 as indicated by the sweep function selected. 3-66. The SWEEP output is an output frequency-re-
e. Control output power with POWER LEVEL: out- lated positive voltage to provide a time-frequency
put power is maximum at 10, minimum at 0. POWER axis for displaying swept-frequency measurements.
LEVEL is uncalibrated but has an attenuation range This positive voltage has fixed range, typically 0 to
15 volts, irrespective of sweep width with zero always
of at least 30 db with unleveled output, 10 db with coincident with the sweep start frequency and+l5 volts
leveled output. always coincident with the sweep stop frequency.
f. Internally square wave or externally amplitude With automatic and triggered sweeps SWEEP output
modulate the RF output. See Amplitude Modulation. is a linear ramp synchronized with the RF sweep.
During manual sweeps the SWEEP output voltage
g. Use automatic RF power leveling to stabilize change is concurrent with output frequency change.
output level and improve source match. See RF SWEEP output functions with start-stop, marker, and
Power Leveling.
AF sweeps in the AUTO, MANUAL and TRIG modes.
3-57. During CW operation RF blanking, pen lift,
SWEEP ON, and SWEEP output are not operational. 3-67. THE SWEEP REFERENCE OUTPUT.
However, a voltage proportional to output frequency 3-68. The rear-panel SWEEP REF output is adirect-
is available at the rear-panel SWEEP REF output. coupled positive voltage proportional to Oscillator
output frequency. SWEEP REF is typically +4 volts
3-58. MANUAL. at the lowest frequency in the Oscillator range, +70
3-59. The manual sweep mode permits manual tuning volts at the highest frequency. Voltage change is con-
current with output frequency change, the actual range
between the end frequencies of the start-stop, marker, and dc limits being determined by the RF sweep width
or A F sweep. Any of the amplitude modulation func-
tions may be used with manual sweep, and RF output and its location in the Oscillator frequency range.
can be leveled or unleveled. Both the SWEEP and SWEEP REF is operational with all sweep functions
SWEEP REF outputs are operational during manual and modes.
sweeping, but RF blanking, pen lift and the SWEEP 3-69. THE PENLIFT.
ON indicator do not function.
3-70. The rear-panel PENLIFT terminals furnish a
3-60. To sweep a frequency range manually, set con- sweep-synchronized writing control for graphic re-
trols for the desired sweep function using the appro- corders equipped to write in response to a remote
priate instructions from Figures 3-3, 3-4, or 3-5 short circuit. The PENLIFT terminals are shorted
but set SWEEP SELECTOR to MANUAL and use during the RF sweep, open between sweeps. The pen
MANUAL SWEEP to vary output frequency. Clock- lift control is operational during AUTO and TRIG
wise rotation varies output frequency toward the stop sweeps in the two slowest sweep time ranges only.
3-10 02280-1
WWW.HPARCHIVE.COM |
ACEC
