Section IV Model 683C
Paragraph 4-5 cont?d
5) Tune the wavemeter to other frequencies and check the wavemeters at each step, nd computing the error.
the dial reading. For sweeps less than full band the specification is
+25%, -15% or *3 mc, whichever is greater. If the
afrequency is within specifications for both proce-
C. SWEPT-FREQUENCY OPERATION. dures (with A FREQUENCY at 2.1K through all posi-
tions of the RF SWEEP RATE switch and with RF .
1) Set up the equipment as shown in figure 4-2. SWEEP RATE at 16K through all positions of AFRE-
QUENCY) then the A FREQUENCY switch is within
Note: Although this procedure can be performed with
one wavemeter, considerable time is saved when - specifications at all other settings.
three wavemeters are used.
D. TRIGGER CHECK.
2) Set sweep oscillator to rated cw output and then
rotate SWEEP SELECTOR to RECUR. 1) Set up equipment as shown in figure 4-2, except
that no wavemeters are required. ;
3) RF Sweep Length:
2) Rotate RF SWEEP RATE control to 1.6K.
a. Rotate the A FREQUENCY switch to 2.1K and
the RF SWEEP RATE switch to 160K. Be sure 3) Rotate A FREQUENCY control to 2.1K, with
the AFREQLJENCY VERNIER is full clockwise, VERNIER fully clockwise.
in CAL. position. Set the FREQUENCY dial
for 4 kmc (gc). 4) Rotate SWEEP SELECTOR to TRIG.
b. Set the wavemeters to 2, 3, and 4 kmc (gc). 5) Push the MANUAL TRIGGER button and observe
The 2 kmc (gc) pip should occur near the end rf sweep display on the cro screen. See specifications
of the sweep trace. in subparagraphs C3d and C4.
c. Adjust the horizontal gain of the oscilloscope 6) A positive 20-volt pulse (3 v/psec or less rise
until the 2 and 4 kmc (gc) pips are exactly time) applied to the EXT. TRIG. jack will also initiate
8 cm apart. a sweep.
Note: 4) 2-4 kmc c = 250 mc/cm .
E. FREQUENCY STABILITY WITH CHANGING
Therefore a 2.1 kmc (gc) sweep will be repre- LINE VOLTAGE,
sented by a trace approximately 8.4 cm long. 1) Set .up equipment as shown in figure 4-2 (only one
wavemeter is required).
d. With the low-end wavemeter pip at 8 cm and the
high-end pip at 0 cm, sweep length should be 2) Set the A FREQUENCY switch to 6.6 and the RF
between approximately 7.6 cm and 9.2 cm. SWEEP RATE switch to 500.
This represents a rf sweep width of 2.1 kmc
(gc) *I%. 3) Rotate the SWEEP SELECTOR to RECUR.
4) Sweep Linearity: 4) Set the power line voltage to 103 volts.
With the center-frequency wavemeter set for 3 kmc
(gc), the pip should appear at the center of the cro 5) Adjust sweep width to 10 cm. Thus 1 cm = 0.66 mc.
screen at 4 cm i0.2 cm (see figure 4-17). The posi- 6) Adjust the rf output to 2 kmc (gc). (This is the
tion of the center-frequency pip checks the degree of most critical frequency.) Tune one of the wavemeters
linearity between the exponential curve needed on the
helix of the bwo tube and exponential sweep generated to approximately 2 kmc (gc) so that a pip will appear
centered on the cro. Allow frequency to stabilize
by the sweep oscillator. If the two exponentials for about 2 minutes.
coincide at three points, e.g., top, bottom, and
middle, the curves will match at all other points.
7) Increase the line voltage to 127 volts, wait 2 min-
utes and note the final drift of the wavemeter pip on
5) A FREQUENCY Calibration: the screen after the frequency drift has stabilized.
Rotate the RF SWEEP RATE switch counterclockwise Maximum change = 2 mc or about 3 cm on the oscil-
to each position and observe the position of the wave- loscope.
meter pips as in 3d and 4, above. With the low-end
wavemeter pip at 8 cm and high-end pip at 0 cm, F. MODULATION CHECKS.
the tolerance (i 10%) referred to 8.4 cm (end of the
4.1-kmc [gc] sweep) is i0.84 cm. This procedure 1) Set up equipment as shown in figure 4-2, except
verifies that A FREQUENCY switch calibration is that no wavemeters are required.
within specifications at its maximum setting.
2) Adjust the oscilloscope for internal sweep and sync.
If it is desired to check the AFREQUENCY switch Sweep speed should be approximately 0.5 ms/cm.
at the other settings, set the RF SWEEPRATE switch
at 16K and rotate the AFREQUENCY switch through 3) Rotate 683C SWEEP SELECTOR to OFF and
each of its positions, measuring the A frequency with AMPL. MOD. SELECTOR to INT.
4-4 01 130- 1 |
ACEC
HEWLETT-PACKARD
