Model 683C Section T
Paragraphs 1-1 to 1-3
SECTION I
GENERAL INFORMATION
1-1. DESCRIPTION. amplitude modulated by sine or complex waveforms
at any percentage from 0 to lOC%. In addition the
The @ Model 683C Sweep Oscillator is one of several oscillator can be externally frequency modulated or
($3 Electronic Sweep Oscillators which cover major swept in frequency over any portion or all of the 2- to
microwave bands as shown in table 1-1. 4-kmc (gc) range, or if desired the 683C can be simul-
taneously amplitude and frequency modulated.
Table 1-1. Electronic Sweep Oscillators When used for its primary purpose as a sweep oscil-
lator, the internal circuitry provides an extremely
($9 Model Frequency Range wide choice of sweeping rates and bandwidth swept.
The rate of change of frequency is linear with time
682C 1.0 to 2.0 kmc (gc) and adjustable in calibrated steps from 16 mc/sec to
160 kmc(gc)/sec. The frequency range swept can be
683C 2.0 to 4.0 kmc (gc) as small as 2.1 mc or as wide as 2.1 kmc (gc), as
684C 4.0 to 8.1 kmc (gc) selected by the calibrated seven position A FRE-
H01 686C 7.0 to 11.0 kmc (gc) QUENCY switch. In addition, there is a VERNIER
control associated with the A FREQUENCY switch
686C 8.2 to 12.4 kmc (gc) which gives continuous adjustment between the fixed
positions .
687C 12.4 to 18.0 kmc (gc)
The minimum sweep time of the Model 683C is 13.2
milliseconds. The sweep time is determined by the
Sweep oscillators are used as signal sources for a combined settings of the RF SWEEP RATE and the
wide variety of laboratory and production tests. They A FREQUENCY switches. These switches are inter-
provide a high-level relatively constant-amplitude locked by a differential gear drive which automatically
signal that can be rapidly changed in frequency. Thus prevents any combination which would produce a sweep
they permit the characteristics of microwave systems time less than 13.2 milliseconds.
or components to be quickly checked over an entire
band of frequencies. The swept rf output frequency from the oscillator is
linear with time and, by adjustment of the SWEEP
The @ Model 683C Sweep Oscillator covers the com- SELECTOR switch, can be made recurrent or set for
plete S band from 2 to 4 kmc (gc) and uses a backward single sweeps. Single sweeps are started either by
wave oscillator (bwo) tube to generate the rf signal. the front-panel pushbutton or by an external positive
pulse (rise time greater than 3 volts per microsecond).
The bwo tube has several advantages over previously In addition, a sawtooth voltage of approximately
used klystron type microwave oscillator tubes when 25 volts is provided concurrent with each rf sweep
used in sweep sources. to supply a linear time base for an oscilloscope or
X-Y recorder.
The bwo tube output frequency and power level are
determined by the values of applied voltage only.
There are no cavity or reflector voltages to adjust or 1-2. INSTRUMENT COOLING SYSTEM.
track. There is no tendency to switch modes of oscil-
lation. Since frequency and power-level adjustments The instrument is forced-air cooled by a high velocity
fan system. The incoming air is filtered to remove
are electronic, all mechanical problems associated excessive dust. This filter must be inspected fre-
with tunable-cavity Hystron-type oscillators are elim- quently to insure that it is not clogged with dirt. A
inated. Control of frequency and power level are
simple, positive, and straightforward. By use of an dirty filter may restrict air flow sufficiently to cause
rf leveler circuit, which programs the rf power out- excessive heating of the instrument which can cause
early component failure (see figure 4-3).
put from the bwo input, power variations of i1.5 db
are realized, With the rf leveler inoperative, output
power from the bwo is kept constant within 6 db, but 1-3. THREE-CONDUCTOR POWER CABLE.
full power from the bwo tube is obtained. The rf
output power is adjustable from 0 to a maximum To protect operating personnel, the National Electrical
which is not less than 30 milliwatts. Manufacturers? Association (NEMA) recommends that
the instrument panel and cabinet be grounded. All
The Model 683C Sweep Oscillator is versatile. The Hewlett-Packard instruments are equipped with a
output can be either cw or amplitude modulated. An three-conductor power cable which, when plugged into
internal square-wave source provides square-wave an appropriate receptacle, grounds the instrument.
modulation at any frequency between 400and 12OOcps. The offset pin on the power cable three-prongcon-
The instrument can be externally pulse modulated or nector is the ground pin.
0 1 130- 1 1-1 |
ACEC
