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Electromagnetic compatibility (EMC)
Electromagnetic compatibility is one of the most important definitions related with devices operating in the range of very high frequencies.
RF cable network should fulfill regulations of electromagnetic shielding. It cannot radiate energy that exceeds determined level and it should be resistant enough to outer electromagnetic radiation.
If the cable network operates on the same frequencies as other radio-communication services, the radiation of the whole system shouldn't affect their operation.
The radiation generated by each network element or device, in all range of the operation frequencies, shouldn't exceed 1*10-10 W, that is 39dBuV/75ohm.
Also in any channel, while the interference is generated by external electromagnetic field of 3V/m strength in 50MHz 2GHz range, the signal /interference ratio shouldn't be less than 64dB for TV signals and 50dB for FM radio signal.
One of the most important parameters, especially of coaxial cables, is shielding effectiveness. It conditions the possibility of using return channel for bidirectional data transmission.
The shielding factor determines how many times the signal coming out of coaxial cable will be decreased when comparing with the signal in the cable, and vice versa. This parameter is usually measured in 47-862MHz range and it's typical value ranges from 45 to more than 100dB.
It is recommended that subscriber cables connecting outlet with receiver have shielding effectiveness >=45dB in 30-470MHz, >=65 dB in 470-1000 MHz, and >=55 dB in 1000-2150 MHz range. The same figures apply to splitters, tap-offs, multiplexers and sockets. For other cables, the screening effectiveness should guarantee:
Frequency range trunk cable



0.15-1000 MHz >85 dB >75 dB >65 dB
1000-2500 MHz >75 dB >65 dB >55 dB
Shielding factor has to be determined for other network elements and devices, too. Broadband amplifiers should have screen factor greater than maximum output level decreased of 39dBuV. For channel and antenna amplifiers this parameter cannot be lower than 75dB.
Previously determined parameters refer to active and passive cable TV installations operating in the 47-862MHz frequency range. Also SMATV (Satellite Master Antenna TV) devices have exactly defined parameters determining electromagnetic shielding.
In the case of satellite coaxial cables, shielding factor should be greater than 65dB for 47-1000MHz, and 55dB for 1000-2150MHz frequency ranges.
In 30MHz - 25GHz frequency range in any 100kHz wide band, any outdoor device cannot exceed the next EIRP ( Effective Isotropic Radiated Power) values:
Value Frequency range
20 dBpW 30 MHz- 960 MHz
43 dBpW 960 MHz - 2,5 GHz
57 dBpW 2,5 - 25 GHz
Also indoor devices shouldn't exceed permissible levels. Electric field strength, measured 10m from the device cannot be higher than 30dBuV/m in 30 - 230 MHz, and 37 dBuV/m in 230 - 960 MHz frequency ranges.
Building devices should be resistant to external electromagnetic fields of 125dBuV/m strength in 150kHz - 1000MHz frequency range. They should also be resistant to interferences coming from power lines.
In 0.15 - 30 MHz frequency range they should keep their parameters when interference level is less than 125 dBuV/m, in 30 - 100 MHz: 120 dBuV/m, and 100 - 150 MHz: 120 -110 dBuV/m (the value decreases linearly with logarithmic frequency increase).
A separate matter that refers to both groups of devices (TV and satellite) is the level of interferences injected into the power network. This level cannot exceed 50dBuV/m.
Frequency range [MHz] Allowable interference level [dBuV]
quasi-peak mean
0.009-0.15 doesn’t exist doesn’t exist
0.15-5 66-56* 56-46*
0.5-5 56 46
5-30 60 50
>30 60 50
* the value linearly decreases with logarithmic frequency increase
As it was mentioned earlier, shielding factor is one of the most important parameters that determine transmission features and limitations of coaxial cables. Generally, this factor is related with density of copper braid (that is the external dielectric) which causes that customers usually choose cables with high percentage of braid coverage. This percentage indicates which part of dielectric is covered by copper braid. Although braid coverage is important and conditions shielding effectiveness, is not identical with it. Shielding effectiveness is a function of many factors. Its actual value is the only reliable indicator of immunity to external interferences.
Application of cables for transmission of all kinds of signals requires shielding them from external interferences and prevention of leakage of electromagnetic field. The decisive parameter is always screening factor, the parameter tested during certification process. It has to comply with current standards. Other subjective opinions, like the role of percentage of braid coverage, may be deceptive.
According to EN50117 norm, there are the next classes of coaxial cables, depending on screening efficiency: C, B, A, A+, A++.
Taking into consideration cables used in subscriber installations, the highest screening efficiency has TRISET-113 E1015_500, with parameters placing it between A+ and A++.
Classes of screening efficiency


30-1000 MHz

2-3 GHz
















If it regards return channel, one should pay attention to the fact that many catalogs don't show parameters of cables for frequencies lower than 50MHz. Obviously, we should assume that having parameters for higher frequencies we can extrapolate them on lower range, but it will introduce errors to the results. It especially refers to shielding efficiency.
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