How to fix the interferences of coaxial wiring on mobile phone networks
Since the 4G came up we are aware of how mobile phone networks affect television coaxial cable networks. But what happens when occurs exactly the opposite, when coax networks have an impact on mobile networks? Why does it happen? And if the problem is not solved, is it subject to a sanction?
Why coaxial wiring is likely to interfere in mobile networks?
First of all, coaxial wiring not only affects mobile phone networks. In fact it can have an impact on any service that is using the radiofrequency spectrum: Emergency services, radionavigation systems, amateur radio operators, etc.
Examples of bad practices and degraded installations.
Poor executions, degraded elements… or installations that are nothing but a mess. All of them are situations that each and every installer has had to deal with, and they have a negative impact in services that use the radiofrequency spectrum.
All these cases have a common denominator: The shielding of wiring, passive equipment or active equipment is of poor quality or is degraded and radiations are release from the cable itself. Other factors such as excessive ground impedance in the equipment can also play a part.
... anyway, the most common case is depicted below: A terrestrial and satellite amplifying station is radiating satellite frequencies (950 MHz) trough the Yagi antenna affecting communications in the 4G band. This happens because of low cost equipment, which uses poor quality filters (or not filters at all!) to keep price low.
Bad quality amplifying station has an impact on mobile phone bands
Economic sanctions for improper installations
Regulators are responsable to control. In Spain, the UNE 50083 standard is explicit about maximum radiation levels that are considered acceptable in coax wiring installations. What follows is an excerpt from the radiation limits as defined in the UNE50083-8:2002 standard:
|FREQUENCY RANGE||FIELD STRENGTH|
(at 3 meters)
|From 5 to 30 MHz||34 to 27 µV/m||9 kHz|
|From 30 to 950 MHz||27 µV/m||120 kHz|
|From 950 to 2500 MHz||50 µV/m||1000 kHz|
|From 2500 to 3000 MHzz||64 µV/m||1000 kHz|
In Spain, the General Telecommunications Law specifies that administration will manage, plan and control the spectrum and therefore will be responsable to inspect, detect, locate, identify and remove any harmful interferences, irregularities and disturbances in the telecommunication systems. This body has also the power to stablish sanction procedures when required.
Acording to the regulation, that considers the spectrum as a public asset, when an improper installation causes interferences in a spectrum band:
- The first step is to contact the owner of the installation that is causing interferences to request its switch-off.
- In case the owner wishes to switch the system on again, he will be asked to take proper actions in order to avoid the problem showing up again.
- The Regulator will apply economic sanctions against the owner who, by omitting both points above, keeps causing interferences.
Measuring the electromagnetic field strength with PROMAX analyzers
The installers using TV & Spectrum analyzers RANGER Neo or HD RANGER from PROMAX have the tool required to check electromagnetic radiation: the Field Strength function.RANGER NEO ANALYZERS
Measuring electromagnetic field strength with PROMAX analyzers.
With a master aerial, such as the PROMAX AM-030 pointing to the unit that is suspected to be causing an interference, the meter can identify the unwanted electromagnetic field. It is very important to properly configure the meter with the antenna K factor to obtain accurate measurements.WATCH HOW TO USE THE FIELD STRENGTH FUNCTION
The K factor is the ratio between the electric field received by the antenna and the voltage generated at its output, which varies depending on reception frequency. The K factor table for each antenna shows this ratio according to the antenna operating frequency.
When the Field Strength is being measured, the spectrum analyzer shows the level in dBµV/m (dB per 1 µV/m) using a 100 kHz filter. Signal identification and digital measurement functions are disabled since demodulation is not necessary. K factor correction tables previously loaded will be applied.
Field strength measurement in a RANGER Neo TV and spectrum analyzer. The corrections calculated by the meter are displayed at the bottom of the screen.
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