The Australian Communications Authority (ACA) has advised the WIA that
they will proceed with plans to Class
Licence new "low interference potential devices" (LIPDs) using a variety
of new frequency band allocations, but of
particular concern to amateurs is the new allocation at 433.05-434.79 MHz.
Designated as an "All Transmitters" allocation, which means transmitters
using this new allocation could serve a
wide variety of applications including, according to the ACA, wireless
stereo headphones, motor vehicle radio
keys and low powered data transmission systems.
Such applications on this frequency range are supported by the self-same
allocation in a number of European
countries. The specified maximum transmitter output is 25 mW equivalent
isotropically radiated power (EIRP).
While low power transmitters operating in this frequency range will likely
cause interference to amateur FM voice
and packet reception under some circumstances, the greater problem for
amateurs arises from receivers for these
applications being blocked by amateur 70cm transmissions. This is a potentially
severe problem where the
receivers are on all the time, such as with "wireless" audio links between
a CD or cassette player and the
associated amplifier.
Wireless links for audio equipment is a new trend in this consumer product
category. Source equipment such as
CD or cassette players, have an in-built transmitter with the amplifier,
or stereo tuner-amplifier, having an in-built
433 MHz receiver. Without the trailing audio cables, the equipment does
not need to be stacked together, but can
be placed anywhere convenient in a room.
Also in this category are wireless amplifier-loudpspeaker combinations
and wireless headphones. European
manufacturers such as Philips, Sennheiser, Sony and Vivanco, launched a
range of wireless-linked audio products
onto the market there last year. However, they ran into problems in some
countries. Radio keys using the 433 MHz
band caused considerable consternation for car owners as amateur, land
mobile and military stations blocked the
door lock receivers for considerable distances.
The WIA has twice raised objections with the Spectrum Management Agency
to the proposed new allocation in the
70cm band. First, in reply to a letter from the SMA in December last year,
and second in a formal submission in
reply to the SMA's proposal in April this year.
The ACA noted in their Information Package issued in April, which proposed
a series of updates to the 1993 Class
Licence for LIPDs, that there was ". . . a growing interest in this band
for low powered applications sourced mainly
from Europe . . . and related to the long standing designation in that
Region, of the band 433.05-434.79 MHz for
industrial, scientific and medical (ISM) applications."
The WIA's response, delivered to the SMA on 2 May, pointed out the likely
interference problems from amateur
70cm operations, even from stations using frequencies well outside the
433.05-434.79 MHz band.
The WIA band plan provides for FM simplex and repeater operation, RTTY,
SSTV, WICEN and packet radio. The
receiver sensitivities in wireless audio equipment, for example, are apparently
on the order of 100-500 microvolts
per metre. Amateur stations operating between 430 and 440 MHz are capable
of causing widespread
interference, the WIA warned the SMA.
A modest amateur home station operating packet radio or FM voice in the
433-434 MHz segment, running powers
of typically 25-50 watts output to a small gain antenna (typical), would
likely cause blocking at distances up to 1 km
in a suburban neighbourhood. The receiver bandwidths of 433 MHz wireless
audio links are such that sensitivity
falls off only modestly 5 MHz either side of centre frequency. A 100 watt
SSB amateur home station, with a modest
yagi of 10 dB gain could wreak havoc with such wireless systems at distances
up to 5-10 km in suburban
situations.
With the foreshadowed introduction of the Class Licence permitting use
of devices such as wireless audio
equipment and radio vehicle keys, the WIA is writing to the Consumer Electronics
Suppliers Association and
relevant Motor Traders Associations to warn of likely problems should equipment
operating on 433.05-434.79 MHz
be introduced here, and pointing out alternatives.
The WIA's submission in May to the SMA on the LIPD proposal also raised
objections concerning the proliferation
of devices on the 13cm, 6cm and 1.25cm amateur bands, particularly where
amateur satellite allocations are
affected. The lower 50 MHz of the 1.25cm (24 GHz) band is the first primary
amateur band segment above two
metres, and is a satellite band.