ARLA/CLUSTER: Abertura da banda dos 4m (70 MHz) na Austrália

[João Costa > CT1FBF]

Quest for Australian 70 MHz ham radio band

WIA Director *Roger Harrison VK2ZRH* provides an update on the attempt to
gain a 70 MHz band in Australia

This is Roger Harrison VK2ZRH from the WIA Spectrum Strategy Committee with
further details concerning proposed new amateur bands included in the WIA
submission to the ACMA’s update of the Australian Radiofrequency Spectrum
Plan.

This week, I’d like to expand on the WIA’s application for an allocation at
70 MHz.

Back in July 2014, the WIA had signified interest in a 70 MHz amateur
allocation in a submission invited by the ACMA, which flagged the amateur
radio community’s interest.

Historically, in Australia, the 70.0-87.5 MHz band has been used by
commercial, community, government and defence communications services.
There is also a Low Interference Potential (LIPD) band at 70-70.24375 MHz,
with a maximum permitted power of 100 milliwatts.

The WIA has been aware for some time that interest in, and use of,
70.0-70.5 MHz has declined across Australia.

The WIA is pitching for use of an amateur allocation between 70 and 70.5
MHz that aligns with amateur allocations across Region 1, which covers
Europe, Russia, the Mediterranean, Middle East and Africa. These Region 1
allocations are widely known as the four metre band.

Let me digress for a moment.

Spectrum was divided into convenient bands back when technical nomenclature
for the new technology was still being worked out. The bands were based on
wavelength. So wavelengths of 100m to 10m – that is 3 MHz to 30 MHz – was
nominated as the high frequency band, 10m to 1m – 30 MHz to 300 MHz – was
the very high frequency band, 1m to 10cm was the ultra-high frequency band,
and so on.

There was – and is – no other particular technical reason based on
characteristic properties of radio waves for the band divisions – they are
just a convenient reference, an arbitrary name.

So. Back to the WIA’s efforts to obtain a 4m allocation.

The band 69.9 MHz – 70.5 MHz is listed in the “European Table of Frequency
Allocations and Applications� as a secondary amateur allocation. Around 30
countries across Region 1 have granted an amateur allocation between 69.9
and 70.5 MHz.

The International Amateur Radio Union – the IARU – the WIA is a member –
notes that, and I quote – “Nowadays, with the widespread closure of
broadcasting below 87.5 MHz, the advent of cost effective globally
available public mobile telecommunications networks and dedicated networks
for emergency services operating above 400 MHz, the relatively large
antennas required on hand-held devices, impulsive noise susceptibility and
interference arising from sporadic E events in the summer months, the use
of spectrum below 100 MHz has become increasingly unattractive for private
/ professional / business mobile communications.� End quote.

70 MHz is subject to over-the-horizon propagation – a fact known since the
early days of radiocommunications and television broadcasting. Ionospheric
sporadic E will carry 70 MHz signals by single-hop propagation up to 2000
km or so, and up to 5000 km or so by multi-hop, as experience from radio
amateur contacts in Region 1 has shown.

70 MHz signals can propagate between the hemispheres via trans equatorial
propagation, too. Experience in Region 1 with amateur contacts over
distances greater than 7500 km between stations in Africa and the
Mediterranean have demonstrated this.

Not so well known, perhaps, is the propagation research work carried out by
Australian defence scientists back in the late-1960s, with a 72 MHz beacon
located near Darwin being recorded in Southern Japan. Similarly, in that
era, point to point links on 70 MHz and above in South Korea were recorded
by university researchers in Queensland.

So. An amateur allocation at 70 MHz in Australia offers some pretty
exciting possibilities for propagation and intercommunication – locally and
over the horizon. The band would seem to share some propagation
characteristics similar to 6m, on one hand, and 2m on the other hand – but
not really the same as either.

There’s one good way to find out, and that’s to have an amateur allocation
that enables and encourages experiment and experience, which is
subsequently reported in the literature – which increasingly these days
means online as much as in-print.

Advocacy. Education. Support. That’s what we do.

Source WIA News
http://www.wia.org.au/members/broadcast/wianews/
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