ARLA/CLUSTER: Comunicações aeronauticas afetadas pelas estações de radiodifusão

[João Costa > CT1FBF]

Air waves are affecting the Airways

A recent investigation of interference to communications between
pilots and the control tower for aircraft approaching Auckland airport
in New Zealand, highlights the risk of unintended signals being
generated as an unwanted side effect of radio broadcasting.

This investigation took several weeks because of the low level of
signal and intermittent observations of the interference.
It involved considerable RSM staff resource as well as requiring the
hire of an aircraft to trace the source. While not causing a safety
risk, because of the availability of alternative radio channels, the
interference did present a significant annoyance and distraction to
pilots.

When located, the problem proved to be an unwanted spurious emission
from an FM broadcast station transmitter in a community north of
Auckland and was quickly addressed by the broadcaster concerned.

A recent study by the Australian Communications and Media Authority,
checking broadcast stations in Australia, suggests that this sort of
problem is relatively common. Around 28% of the transmitters they
checked showed the production of unwanted emissions. Many of the
emissions were radiated in the aeronautical radiocommunication band of
108MHz to 136MHz, presenting a potential risk to safe operation of
aircraft.

RSM supports the use of external filters as an effective means of
limiting the radiation of spurious signals, and recommends that all
broadcasters should note the tips given in the CBAA news item for
monitoring the health of their transmissions

Radio Spectrum Management