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VK3ZWI > IARU 03.09.00 12:56l 88 Lines 4616 Bytes #999 (999) @ WW
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Subj: IARU R3 Report #8
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From: VK3ZWI@VK3FRS.#MEL.VIC.AUS.OC
To : IARUR3@WW
Band planning for digital modes on HF bands
Introduction
The following is a discussion of the band planning implications of the
expansion of digital modes on the HF bands. Several options for future band
planning guidelines are considered, and a change to the structure of digital
mode band plans is suggested.
Increasing use of digital modes
In recent years there has been a considerable increase in the use of digital
modes on the HF bands. For many years modes such as RTTY enjoyed dedicated
support from a comparatively small number of radio amateurs, but they never
became as popular as CW or SSB because of the need for additional equipment.
The situation has now changed with the universal availability of computers and
their ability to perform advanced signal processing operations. Radio amateurs
now have access to a wide range of communication modes which in most cases
have very simple interface requirements. Modes such as packet radio and AMTOR
have brought digital operation into the mainstream of amateur activity, and
the use of computers allows new modes such as Pactor, Clover or PSK31 to be
developed and come into common use within a very short time.
There is no doubt that digital operation is the primary growth area of amateur
radio, and that the use of digital modes will increase even more rapidly in
the years to come.
The increasing variety of digital modes has posed some band planning problems
, and greater problems are likely in the future. There are two main questions
that should be considered:
(a) Is it necessary to expand the total amount of spectrum available for
digital modes? If so, how can it be done?
(b) Is it possible to improve operating conditions by rearranging the existing
digital sub-bands in our bandplans?
Extra spectrum space for digital modes?
It seems likely that more spectrum will be needed for digital modes in the
future. But this would have a harmful impact upon amateurs using other modes
such as CW and SSB.
It could be argued that with the transition to a 5 wpm Morse qualification -
and the possibility that the ITU Morse requirement will be dropped altogether
- we might expect a steady decline in the use of CW in the coming years. This
may make it possible to expand the digital modes segment downwards without
causing any major dislocation.
Against this is the fact that CW is still a mode of major importance. It is
spectrum efficient, it can be used with cheap and simple equipment, and it is
still the "international language" of amateur radio. Even if the ITU Morse
requirement is abolished in the near future, there is no doubt that there will
still be a high level of CW activity for many years to come.
It should also be remembered that the existing CW segments are often seriously
overcrowded. It would be unwise and unfair to make any significant reductions
in the CW sub-bands in the foreseeable future.
Similar arguments apply to the idea of expanding the digital sub-bands upwards
into the SSB segment. SSB occupies greater bandwidth than CW or digital modes,
but it has a far greater throughput rate. It also provides closer human
contact between radio amateurs than is possible with any non-voice mode.
Finally, the SSB sub-band is also used for image transmission modes such as
SSTV and fax, which are rapidly increasing in popularity. It does not seem
practical to make any significant reduction to SSB sub-bands.
More efficient use of existing digital sub-bands?
In the past, when RTTY was virtually the only digital mode used by amateurs,
it was simple to add an RTTY segment to the band plan. Later it became
necessary to subdivide the RTTY segment to create sub-bands for other modes
such as packet and AMTOR. This process cannot continue indefinitely - there
are now so many digital modes that it is impossible to provide separate band
segments for each of them. Some other solution is needed.
The amount of spectrum required by each mode changes as older modes decline
in favour of newer, more efficient modes. Another consideration is the fact
that some newer modes such as PSK31 occupy far less bandwidth than older modes
such as RTTY, and there is no doubt that the trend towards narrower bandwidths
will continue in the future.
This suggests that much, or possibly all, of the spectrum space required for
digital modes in the future could be found within the existing digital
sub-bands.
This IARU RIII Conference Report was issued courtesy WIA Victoria
www.tbsa.com.au/~wiavic
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