Figure 4-18. Frequency-Time Recorder, Bottom View Showing Main Chart Drive Components.

TM 11-6660-204-25

Figure 4-18. Frequency-Time Recorder, Bottom View Showing Main Chart Drive Components.

4-12. Elimination of Hysteresis Error

4-13. Noise Suppression Diode Alignment

a. Operate the circuit breakers and power switch

Since the types of noise on the received radiosonde

to the ON position.

signals vary with atmospheric conditions and ra-

b. Operate the SIGNAL SELECTOR switch to

d i o s o n d e systems, the noise-suppression diode

S.C. and let the recorder warm up for 15 minutes.

should be aligned only when the radiosonde signals

c. Unlock the control panel and draw the recorder

are being received. An oscilloscope will be required to

forward sufficiently to reach the split gear assembly

align the noise suppression diode properly.

on the bottom side (fig. 4-18). Apply finger pressure

a. Observe the signal at Jack J303 (fig. 3-15). If

the signal is not noisy, set noise suppression switch

to the rim of the split gears and force the pen slightly

S301 (fig. 3-15 to the OUT position. If the signal is

to the right; then remove the force slowly, so that the

noisy, set noise suppression switch S301 to the IN

pen carriage will not jump back into its former posi-

tion. Let the pen record in its percent position for 10

position.

b. Rotate potentiometers R304 and R306 (fig.

or 15 seconds. Next, force the pen a little to the left.

3-15) to their maximum clockwise position.

Release slowly, and again allow a short chart record-

c. Connect the oscilloscope between jack J307 and

ing. If there is any difference between the two record-

ground.

ings (hysteresis error), this difference should be cen-

d. If noise appears on the oscilloscope at jack

tered on the chart zero line by adjusting the REC.

J307, adjust potentiometers R304 and R306 as fol-

lows: