Idle Channel (Residual) Noise Test

TM 11-5895-1012-10

signal generator, a signal distortion analyzer, and an

ure 6-1.

oscilloscope. These items are described below:

(3) Procedure. The receiving station will measure

(1) Signal Generator SG-860/GGM-15(V). This

and record the noise level indication. This measure-

unit generates data and telegraph signal outputs with

ment will be taken with the Noise Measuring Test Set

controlled distortion at speeds up to 9600 baud. Var-

set for C message filtering and will be measured in

ious message options are available for Baudot or

dbrnc.

ADCII codes.

(4) Performance Standard. Refer to the Technical

(2) Signal Distortion Analyzer TS-2862/

Services Schedules (table 4-2) for the maximum allow-

able noise for the channel being tested. The noise

GGM-15(V). This unit performs three major func-

tions: distortion analysis, distortion monitoring, and

measured during this test will not exceed the level

specified by the Technical Services Schedule.

error rate determination.

(3) Oscilloscope OS-20/GGM-15(V). This unit is

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

used to display the signal under analysis.

plished in the same manner as station to station test-

l. Accessory Items. The accessory items listed below

ing except the local station acts as both transmitter

are required for some of the tests in this chapter.

and receiver.

(1) Test Tone Source. 1000 Hz at - 10 dbm0.

6-5. Frequency Response Test (fig. 6-2)

(2) Resistors. Two 300 ohm 1%, 1 watt resistors

and one 150 ohm 1% 1 watt resistor are required.

a. Purpose. This test will measure frequency

(3) Transformer. An center-tapped audio trans-

response of a circuit either between stations or within

former with a 1:1 ratio and an 600/600 ohm impe-

a station and determine circuit compliance with the

dance is required.

standard operating requirement. Frequency response

is the capability of a system or component to pass a

6-3. Test Conditions

group of frequencies with the original amplitude rela-

a. Patch Panels. Unless otherwise specified, station

tionship relatively intact.

to station tests will utilize two equal level patch panels

b. Test Equipment. The following test equipment is

while in-station tests will utilize one equal level and

required to perform this test:

(1) Transmission Test Set.

one primary patch panel.

b. Service Conditions. Unless otherwise specified,

(2) Noise Measuring Test Set.

the circuit to be tested will he out of service. However,

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

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

it will be aligned and conditioned for the circuit

and arrange for one station to act as transmitter and

characteristics and transmission levels specified in the

one as receiver. When test has been completed reverse

applicable TSO.

roles.

6-4. Idle Channel (Residual) Noise Test

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

(fig. 6-1)

act as transmitter, prepare the transmitting circuit

a. Purpose. This test will measure idle channel (resi-

shown in figure 6-2 and set the equipment as follows:

(a) Patch panel impedance selectors at 600

dual) noise on a circuit between stations or within a

ohms.

station and will determine circuit compliance with

(b) Patch panel frequency control at less than 5

standard operating requirements. Idle channel or resi-

KHZ

dual noise is a combination of all of the disturbances

(c) Transmission Test Set for 1000 Hz, -10

occurring within the channel bandwidth and includes

dbm0 output to the transmit circuit.

noise caused by nonlinearities, crosstalk, and thermal

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

effects.

as receiver, prepare the receiving circuit shown in fig-

b. Test Equipment. The following test equipment is

ure 6-2 and set the equipment as follows:

required to perform this test:

(a) Input selector set for 600 ohms.

(1) Noise Measuring Test Set.

(b) Filter selector set for 15 Hz.

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

(c) Sensitivity set for 0.

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

(3) Procedure. While the transmitting station var-

and arrange for one station to act as transmitter and

ies the frequency and holds the input level constant,

one as receiver. Perform the procedure below and then

the receiving station will record level readings on the

reverse roles and repeat the procedure.

Noise Measuring Test Set for the following fre-

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

quencies: 300 Hz, 400 Hz, 500 Hz, 600 HZ, 700 Hz, 800

act as transmitter, prepare the transmitting circuit

Hz, 1000 Hz, 1200 Hz, 1400 Hz, 1600 Hz, 1800 Hz,

shown in figure 6-1.

2000 Hz, 2200 Hz, 2400 Hz, 2600 Hz, and 3000 Hz

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

(4) Performance Standard. Maximum deviation

as receiver, prepare the receiving circuit shown in fig-

6-2