GY/T 195-2003Specifications and methods of measurement on two-way subscriber port used in CATV systems (English PDF)

5.1 General requirements

The appearance should be neat, and the surface should be free of obvious dents, scratches, cracks, burrs and deformation; the plating coating should not be blistering, cracking and peeling; gold the attachments shall be free from rust and mechanical damage; the pouring material shall not overflow.

Structures and components should be fastened and not loose; the text and graphic symbols describing functions should be complete, correct, clear and firm;

The shape symbol shall comply with the relevant provisions of GB 5465.2-1985.

The input port and user port connectors should be metric F headers.

5.2 Technical requirements

The technical requirements of the two-way user port of the cable television system are shown in Table 1.

Table 1 Technical requirements for two-way user ports in cable television systems

Technical index

dB serial number items Frequency Range MHz two-hole three-hole 5 ~ 65 >=45.0 >=45.0 Input port-TV port 87 ~ 1000 <=5.0 <=6.0 Input port-DP port 5 ~ 1000 <=5.0 <=6.0 5 ~ 65 >=30.0 insert loss Input port-FM port 87 ~ 108 <=14.0 5 ~ 108 >=30.0 TV port-FM port 108 ~ 1000 >=28.0 5 ~ 65 >=60.0 >=60.0 TV port-DP port 87 ~ 1000 >=26.0 >=22.0 5 ~ 65 >=60.0 mutual isolation FM-DP 87 ~ 1000 >=35.0 5 ~ 65 >=16 >=16 87 ~ 550 >=16 >=16 input port 550 ~ 1000 >=14 >=14 108 ~ 550 >=16 >=16 TV port 550 ~ 1000 >=14 >=14 FM port 87 ~ 108->=16 5 ~ 65 >=16 >=16 87 ~ 550 >=16 >=16 reflection loss DP port 550 ~ 1000 >=14 >=14 shield attenuation-5 ~ 1000 >=90 >=90

5 Withstand voltage input-2kV AC voltage, no breakdown for 1min

6.1 Measurement of insertion loss and isolation

6.1.1 Measurement block diagram

see picture 1.

input Output

Input and output

Measured in both directions User port the internet Analyzer

Figure 1 Block diagram of insertion loss and mutual isolation measurement

6.1.2 Measurement procedure

a) Set the working frequency range of the network analyzer to the working frequency range of the bidirectional user port under test;

b) calibrate the network analyzer;

c) Connect the bidirectional user port under test and the network analyzer according to Figure 1;

d) read the maximum and minimum levels in the operating frequency range;

e) Measure the insertion loss of input port to TV port, input port to DP port, and input port to FM port according to the frequency range requirements in Table 1.

Consume

f) Measure the isolation between TV port to FM port, TV port to DP port, and FM port to DP port according to the frequency range requirements in Table 1.

If a frequency sweeper is used for measurement, it should meet the relevant regulations in GY/T 140-1999 and GB/T 11318.1-1996.

A 75ohm termination load is applied to all unmeasured device ports.

6.2 Measurement of reflection loss

6.2.1 Measurement block diagram

See Figure 2.

Input and output

The internet

Analyzer

Measured in both directions User port

Figure 2 Block diagram of reflection loss measurement

6.2.2 Measurement procedure

a) Set the working frequency range of the network analyzer to the working frequency range of the bidirectional user port under test;

b) Perform "open", "short", and "match load" calibration on the network analyzer;

c) Connect the bidirectional user port under test and the network analyzer according to Figure 2;

d) According to the requirements of Table 1, directly read out the minimum value of the reflection loss in different frequency bands of the input port, TV port, FM port and DP port, which is the measurement.

value.

The input and output of the bidirectional user port under test shall be measured separately.

If a frequency sweeper is used for measurement, it should meet the relevant regulations in GY/T 140-1999 and GB/T 11318.1-1996.

A 75ohm termination load is applied to all unmeasured device ports.

6.3 Measurement of shielding attenuation

Should comply with the relevant provisions of 5.4 of GY/T 140-1999.