Since the appearance of 4G we have been aware of how mobile phone networks affect coaxial cable television networks. But what happens when the scenario is reversed and coaxial networks interfere with mobile networks? Why does this happen? And if it is not solved, is it a reason for sanction?
Why do coaxial cables interfere with mobile networks?
First of all, coaxial cable networks do not only affect mobile phone networks. In reality, they can affect any service that uses the radio frequency spectrum: emergency services, radio navigation, radio amateurs, etc. Poorly executed installations, degraded elements or simply botched jobs.
These are situations that every antenna operator has encountered and that have a negative impact on the services that use the radio frequency spectrum. The common denominator of all these cases is that the shielding of the cable, of the passive equipment or of the active equipment is of poor quality or has deteriorated and is allowing radiation to be emitted to the outside from the cable itself. Other factors may also play a role, such as excessive impedance in the equipment grounding. … although the most common case is the one illustrated in the image below: A terrestrial and satellite signal amplifier station is radiating the 950 MHz satellite frequencies through the Yagi terrestrial antenna, affecting communications in the 4G band. This happens by using low-cost equipment that, to lower its price, integrates low-quality filters (or, directly, lacks them!).
En Spain, the General Telecommunications Law specifies that "inspection, detection, location, identification and elimination of harmful interference, irregularities and disturbances in telecommunications systems are integrated into the administration, management, planning and control of the aforementioned spectrum, beginning , where appropriate, the appropriate sanctioning procedure”. The K factor is the relationship between the electric field collected by the antenna and the voltage generated at its output, which is variable according to the reception frequency. The K factor tables of the antennas show this relationship according to the working frequency of the antenna.
Penalties for deficient facilities
The UNE 50083 standard explicitly includes the radiation levels that are considered admissible in coaxial cable installations. Below is an extract from the table of radiation limits included in the UNE50083-8:2002 standard. According to the regulations, which consider the spectrum as a public good, when a deficient installation causes interference in a spectrum band: The first step will be to contact the owner of the installation that causes interference to request its deactivation. The owner will be advised to take appropriate actions to prevent recurrence of the problem when the installation is reactivated (if the owner wants the reactivation to occur). The Administration will apply sanctions against the owner who, by omitting the two previous points, continues causing damage with the interference of his installation. Installers using PROMAX RANGER Neo or HD RANGER field strength meters have the necessary tools to check electromagnetic radiation thanks to the Field Strength function.
With a standard antenna such as the PROMAX AM-030 pointed towards the element that is suspected of causing interference, it is possible to identify if it is really radiating an unwanted electromagnetic field. It is very important to have configured the meter with the K factor of the antenna to obtain accurate measurements. When Field Strength is being measured, the spectrum analyzer takes the level measurement in dBμV/m (dB relative to 1 μV/m) using a 100 kHz filter. Since it is not necessary to demodulate the signal for this process, the signal identification and digital parameter measurement functions are disabled. At the same time, the corrections defined in the K factor table that will have been loaded in the equipment are applied.
