There are Video Picture (TV Pictures) send by using OSN1500 and encoder/decoder equipments (Huawei Equipments) as the following:
Original TV Picture -- DS3_Out port of Encoder (DXT8800) � PL3_IN port of OSN1500 -- out Loop in PL3 -- PL3_OUT port of OSN1500 -- DS3_IN port of Decoder (DXT8300) -- TV Picture Monitor
At the receiving point by make loop from the OSN1500, there were hums resulted on the pictures on the TV Picture Monitor.
When we checked the room we get there are radiations generated from the electromagnetic interference (EMI) sources of Power Equipments in the room that effected on the picture and generated hums, this because the picture pass to more processes in the equipments such as time-frequency conversion, quantization, encoding, and transmission point. So it will be easy for the picture at these processes to effect by the radiations.
So the electromagnetic interference (EMI) sources can affect the communication quality by causing cross-talk and stray noise, and even result in communication interruption, the electromagnetic interference (EMI) sources such as:
- Waveform distortion of the power supply network caused during the operation of large equipment.
- Natural interference sources such as external radiation such as spatial electromagnetic wave.
- Natural interference sources such as terrestrial magnetic field... And others sources.
1. We checked the Grounding points for the OSN1500 (SDH), Encoder (DXT8800) and Decoder (DXT8300) equipments, and we get it ok.
2. We connect the Grounding for the Generated Device of the original TV Picture and the TV Picture Monitor and make other devices and the result was not ok.
3. We checked the picture by other Picture Monitor, and the result also hums on the pictures.
4. We make loop from Encoder (DXT8800) to Decoder (DXT8300) without use OSN1500 Equipment, and the result also same.
5. We make loop from the Original Picture to the TV Picture Monitor (without use OSN1500 and Encoder/Decoder Equipments), and the result was ok!!
6. We checked and changed all cables, and the result also hums.
7. We checked the parameters of the OSN1500 and Encoder/Decoder equipments, and we got it ok.
8. We checked by other port in PL3 board in the OSN1500 and the board in encoding equipments and the result also hums on the picture.
9. We replaced the position of the OSN1500 and Encoder/Decoder Equipments to other room, and the result was ok no any hums in the picture.
In the site survey for the Picture transmission it should survey if there is radiation on the room that generated from the power equipment, also check the ground for each points.
Also you should care for the interference from either inside or outside the equipment or the application system, affects the equipment through conductive modes such as capacitance coupling, inductance coupling, electromagnetic wave radiation, common impedance (including grounding system) and cable (power and signal cables). In terms of external relations of the equipment, interference is from the signal cable, power cable, grounding system and spatial electromagnetic wave.