Terminal Impedance Test of Transmit Circuit

TM 11-5895-1012-10

and arrange for one station to act as transmitter and

a circuit between stations or within a station and will

one as receiver. Perform the procedure below and then

determine circuit compliance with standard operating

reverse roles and repeat the procedure.

requirements. Impulse noise consists of transient

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

waveforms of various shapes, durations, and ampli-

as receiver, prepare the receiving circuit shown in fig-

tudes. It can be caused by natural disturbances such as

ure 6-10.

lightning or atmospheric static, or by manmade dis-

(2) Transmitting Circuit. If the local station is to

turbances.

act as transmitter, prepare the transmitting circuit

b. Test Equipment. The following test equipment is

shown in figure 6-10 and set the equipment as fol-

required to perform this test:

lows:

(1) Impulse Noise Counter.

(a) Jumper the transmission test set as shown in

(2) Terminating plugs (600 ohms) and patch cords.

figure 6-10.

c. Station-to-Station Test. Contact distant station

(6) Set the transmission test set patch panel out

and arrange for one station to act as transmitter and

put impedance selector to 600 ohms.

one as receiver. Perform the procedure below and then

reverse roles and repeat the procedure.

put impedance selector for bridging`

(1) Transmitting Circuit. If the local station is to

(d) Set the transmission test set patch panel fre-

act as transmitter, prepare the transmitting circuit

quency selector at less than 5 KHz.

shown in figure 6-9.

(e) Turn on the transmission test set voltmeter.

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

(3) Procedure. Calibrate the transmission test set

as receiver, prepare the receiving circuit shown in fig-

for 1000 Hz and a 1 volt (V1) voltmeter reading.

ure 6-9 and &the impulse noise counter as follows:

Switch the calibrate-measure switch back to the meas-

(a) Power switch to ON.

ure position, and read the voltage (V2) on the trans-

(b) Hold switch to OFF.

mission test set voltmeter. Calibrate the transmit im-

(c) Bridge/Term switch to Term.

pedance from the following expression:

(d) Weighting selector to Voice.

(e) Input impedance at 600 ohms.

(f) Timing at 15 minutes.

V1 = transmission test set open circuit output voltage

(g) Sensitivity controls set so that all impulse

V2 = t-on teat set output voltage when termin-

hits above the reference level specified in the technical

ated at the receiving circuit.

schedules (table 4-2) will be registered or recorded.

(4) Performance Standard. The permissable ter-

(3) Procedure. Receiving station will record all im-

minal impedance is 600 ohms 10%.

pulse hits above the reference level specified in the

d. In-Station Test. In-station testing is accom-

technical schedules (table 4-2).

plished in the same manner as station to station test-

(4) Performance Standard. The maximum number

ing except the local station acts as both transmitter

of impulse hits permissable in the 15 minute time pe-

and receiver.

riod is 15.

6-12. Terminal Im

d. In-Station Test. In-station testing is accom-

plished in the same manner as station to station test

the terminal im-

ing except the local station acts as both transmitter

pedance of the receive circuit between stations or

and receiver.

within a station and determine circuit compliance with

6-11.

Terminal

Impedance

Test

Trans-

the standard operating requirements. Terminal im-

mit Circuit (fig. 6-10)

pedance must be kept with specifications to preclude

impedance mismatch which will result in poor fre-

a. h-pose. This test will measure the terminal im-

quency response, excessive loss of signal power, or im-

pedance of the transmit circuit between stations or

proper signal level measurements.

within a station and determine circuit compliance with

b. Test Equipment. The following test equipment is

the standard operating requirement Terminal im-

required to perform this test:

pedance must be kept within specifications to preclude

(1) Transmission Test Sets (2 required).

impedance mismatch which will result in poor fre-

(2) Terminating plugs (600 ohms) and patch cords,

quency response, excessive loss of signal power, or im-

c. Station-to-Station Test. Contact distant station

proper signal level measurements

and arrange for one station to act as transmitter and

b. Test Equipment. The following test equipment is

one as receiver. Perform the procedure below and then

required to perform this test

reverse roles and repeat the procedure.

(1) Transmission Test Set.

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

(2) Terminating plugs (600 ohms) and patch cords.

as receiver, prepare the receiving circuit shown in fig

c. Station-to-Station Test. Contact distant station

6-12