ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación descargar pdf (Pagina 173)

broadcast digital quality radio programs over very long-range links and also to

transfer data at rates of some tens of kilobits/s.

The disturbances caused by PLC networks for amateur radio operators and the

DRM have been the subject of many discussions to make it possible for various tech-

nologies to coexist. These discussions have led the developers of PLC technologies to

include filtering techniques for frequencies already used by other radio technologies.

These techniques, called “notching,” consist of listening to the radio channels to

readjust or take away some frequencies.

Dynamic Notching of Frequency Bands

As illustrated in Figure 8.3, when the PLC network notices that the f1 and f2 frequencies are

used, it takes away the frequency bands containing f1 and f2 in its authorized spectrum.

These frequency bands are still off throughout the use of f1 and f2, then on again as soon as

these frequencies are no longer used.

This dynamic technique is based on listening to the signal-to-noise level measured in

dB for each frequency band.

Low Bit Rate PLC

Mainly used in home automation and car automation (industrial bus of automotive

vehicles), the frequencies authorized for low bit rate PLC are described by the

Cenélec in the EN-50065-1 standard. This standard defines the utilization charac-

teristics of all the frequency bands between 3 kHz and 148 kHz. The PLC signal

transmission power is limited by the maximum permitted voltage, which is 3.5V for

these frequency bands.

Table 8.1 summarizes the characteristics of low bit rate PLC frequency bands.

As a reminder, the AM radio band covers the 162 to 252 kHz spectrum.

154 Installation

Figure 8.3 Notching of congested frequencies

1 2 ... 168 169 170 171 172 173 174 175 176 177 178 ... 348 349

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ZyXEL Communications PLA-470 V2 - V3.0.5 Guía de instalación Pagina 173