Figure 6-11. Terminal impedance test for receive circuit.

TM 11-5895-1012-10

Figure 6-11. Terminal impedance test for receive circuit.

6-14. Composite Signal Transmission

act as transmitter, prepare the transmitting circuit

Level Test (fig. 6-13)

wn in figure 6-12 and set transmission test set as

ws:

t of operating conditions

(a) Jumpered as shown in figure 6-12.

rather than a measurement of circuit parameters. As

(b) Patch panel impedance selectors at 600

such, this test is not applicable as an in-station or

ohms.

maintenance test.

(c) Patch panel frequency selector at less than 5

b. Test Equipment. A noise measuring test set and

KHz.

patch cords are required to perform this test.

(d) Turn on voltmeter.

c. Procedure. Prepare the test arrangement shown

(2) Receiving Circuit. If the local station is to act

in figure 6-13 and set the noise measuring test set for

as receiver, prepare the receiving circuit shown in

600 ohms impedance and for bridging. Set the filter

figure 6-12 and set the frequency selective voltmeter

selector for high pass filtering. The circuit being tested

as follows:

should be in service and the connection should be made

(a) Input impedance control at 600 ohms.

at the VF patch panel. Read and record the indications

(b) Bandwidth to 200 or 250 Hz.

on the noise measuring test set.

(3) Procedure. Transmitting station will calibrate

d. Performance Standard. The required composite

the transmission test set for a 700 Hz, - 10 dbm0 out-

level is the reference level minus 13 dbm0.

put. Receiving station will measure the circuit level of

6-15. Phase Jitter Test Using Oscil-

the fundamental (700 Hz), second harmonic (1400 Hz),

third harmonic (2100 Hz), ad fourth harmonic (2800

Hz). Calculate the total harmonic distortion using the

a. Purpose. This test will measure phase jitter of a

following expression:

circuit between stations or within a station and deter-

mine circuit compliance with minimum operating

requirements. Phase jitter is the instantaneous de-

viation from the average phase of the signal and may

(4) Performance Standard. The maximum permis-

be caused by channel induced phase noise or by

total harmonic distortion is -40 dbm0.

additive amplitude noise. Phase jitter may be

d. In-Station Test. I n - s t a t i o n t e s t i n g i s a c -

measured using an oscilloscope or using a phase jitter

complished in the same manner as station to station

meter. The procedure for measuring phase jitter using

testing except the local station acts as both trans-

an oscilloscope is given below. The procedure for

mitter and receiver.

6-15