ARLA/CLUSTER: Como identificar potenciais fontes de interferência.

[João Gonçalves Costa]

The Australian Communications and Media Authority has a masthead and distribution amplifier fact sheet, and a media article on electrically powered fences - both which can cause interference.

In marginal TV reception areas it is finding faulty, due to age or misuse, masthead amplifiers that radiate a signal affecting TV viewing, mobile phones, two-way radios and heard on the amateur radio bands.

Similar problems are known to exist in other countries which have pockets of poor TV or FM radio reception that need amplification and to keep otherwise wandering animals in a paddock.

ACMA field officers have found the amplifier devices either overloaded to distortion, internally mixing a multitude of high level signals, or going into self-oscillation.

Distribution amplifiers are also designed to feed a number of TV sets from a single antenna, but never to oscillate and become an unintended radiator.

One was tracked and disabled by the ACMA recently in a block of flats in inner suburban Melbourne that was causing interference to a nearby Telstra mobile phone tower.

Meantime, the ACMA in the Hoofbeats magazine read mainly by horseowners, warns then about the interference that may be caused by faulty electric fences.

The fact sheet and article give helpful installation and operational advice, and how to avoid fines the ACMA may issue if it enforces the Australian Radiocommunications Act.

Jim Linton VK3PC
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