Power-Line Networking Can Interfere With DAB, FM

BBC tests find localized reception problems with in-home PLA devices
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Broadband over power lines (BPL), the use of mains electricity delivery lines to carry Internet and other data services to homes, has raised a good deal of concern among amateur radio operators and some broadcasters due to interference with HF transmissions.

Although BPL technology remains in limited use at this point, a related technology, power-line adaptors (PLA), are finding growing use for the distribution of Internet connectivity throughout a home. With PLAs, a node that plugs into a standard electrical outlet is connected to a router. Additional nodes can be plugged into any other electrical outlet to create a new network connection point.

While traditional BPL operates only in HF spectrum, PLAs operate in HF and VHF, including in spectrum used for FM and DAB radio broadcasts.

In a report issued in March, BBC engineers tested the effect of off-the-shelf PLAs on standard FM and DAB receivers.

The laboratory test and two in-home tests found that PLAs do cause interference to indoor portable radios, even when connected to an external antenna.

Interference to FM receivers manifested itself in the form of popping and ticking noises when the PLA was idle and a “tearing” sound that could make listening impossible when the PLA was busy. For DAB, the interference could cause the digital signal to drop entirely.

In both cases, the stronger the over-the-air FM or DAB signal, the lesser degree of interference from the PLAs.

The white paper is a preliminary examination of the issue, however, and the authors state that additional research should be done to look at a wider range of devices and listening conditions.

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