A brief technical/operational analysis of the new Australian State/Territory
Coast Radio Network
Please note that the following represents an objective, professional opinion.
To my mind, the new State based network suffers from a number of shortcomings, viz:
1. The utilisation of scanning receivers;
2. The lack of dedicated working channels; and
3. The use of new operations staff.
1. Scanning receivers
Many HF radio networks use scanning receivers very successfully (including, of course, shipboard DSC receivers). However, scanning receivers normally operate with some kind of selective calling muting system. That is, the receiver will not stop the scanning sequence until it detects a valid calling data string (dot pattern, phasing signal, whatever). The use of this kind of muting system effectively eliminates false triggering - the receiver will ignore static/noise bursts and other signals.
Obviously, the new stations will be operating in voice mode only. Using a scanning receiver in voice mute mode is only successful if the channels being scanned are free from noise and interference. As soon as any kind of signal appears on channel, the receiver will stop the scanning sequence, and wait until the signal stops before resuming. The receiver will be virtually locked on the first channel in the scanning sequence with any kind of signal. It is for this reason that voice mute scanning is not widely used in HF networks.
Digital Signal Processing (DSP) can be used to reduce the effects of noise and interference, however DSP will not remove on frequency voice signals - after all, DSP is designed to enhance intelligibility of signals on the frequency to which the receiver is tuned.
Of the 3 marine channels being scanned, 6215 suffers from Asian interference at night (24 hrs/day at Darwin), and 8291 is often used by foreign fishing boats and the like for inter-ship chat. As I type this, there are two Asian stations engaged in a long conversation on 6215. The high levels of traffic on these 2 channels will severely disrupt the scanning sequence.
The other alternative to voice mute scanning is to use time based scanning - i.e. the receiver is switched through the channels in its scanning table in a finite time. For example, 5 seconds on 4125, 5 seconds on 6215, 5 seconds on 8291, regardless of signals present.
The critical disadvantage of scanning receivers for a distress and safety application is that a continuous watch is not being maintained on all channels - if voice mute mode is being used, the receiver will normally stop on the channel with the most traffic/noise/interference. If time based scanning is operating, each channel is only being monitored effectively for 33% of the time.
Whichever system is used, there is a very strong potential for calls to be missed on one of the distress channels.
Radio Stations maintaining a distress and safety watch normally use dedicated receivers for each channel - this ensures that a truly continuous watch is maintained.
2. Lack of working channels
The ITU International Radio Regulations, and hence the Australian spectrum plan restricts the use of 4125, 6215 and 8291 kHz to distress and safety traffic.
These regulations effectively prohibit the transmission of long messages on distress and safety channels. A brief radio check is acceptable, however if stations wish to pass position reports or any other kind of lengthy non-distress, urgency or safety message, another frequency must be used. Apart from 8176 kHz (to be used briefly for MSI broadcasts), there appears to be no other working channels assigned to the new network. This is a critical oversight, in my opinion.
What are small vessels to do if they wish to pass a long message (such as a position report) to the new network?
Flout the Radio Regulations?
It can be argued that the Australian Communications Authority is effectively encouraging the breaking of their own regulations by not insisting on the assignment of working channels for the new network.
The State Government (and the Australian Communications Authority) web sites advise users to contact a volunteer station if they have a long message to pass.....
Why install a completely new Coast Radio Network if it can not fulfill such a basic requirement as providing working channels?
To complicate matters, the previous Coast Radio Network working channels (2201, 4426, 6507, 8176 and 12365 kHz) are now used for the automated broadcast of MSI from the Charleville station - the assignment of these channels to Charleville is understandable - it simplifies things for users. Sensible in the short term - yes.
In the long term??
Users of Australian marine radio stations are a conservative lot. They are highly resistant to change. I was working for the Australian Maritime Safety Authority when the previous 13 Australian Coast Radio Stations were reduced to 7. Much was made of the extended performance available with the 8, 12 and 16MHz GMDSS radiotelephone channels. Indeed, this extended range was used as the rationale to close much of the then Coast Radio Network.
So, what happened? In a word - nothing. The small vessel operators continued to use 2182, 4125 and 6215 kHz just like they always did. In the 10-odd years since the introduction of 8291, 12290 and 16420, the level of utilisation of these channels by small craft has been very low, if non-existent.
I well remember sitting at the VIP, VID, VIT, VIB, VIS and VIM consoles and hearing very little Australian traffic on 8, 12 and 16 MHz - ask any Radio Officer from the previous network - he or she will tell you that the only call they received on these channels were from merchant vessels seeking radio checks during annual surveys.
The point I am making is that the average small vessel operator is a creature of habit. He/she will expect any new network to replicate the services of the old - that is, provide a working channel for passing of traffic.
3. New ops staff.
Providing a professional SOLAS voice watch on HF is a specialist skill. It is not the same as casually listening to a HF or VHF circuit, or even operating a military radio network.
Imposing this burden on operators whose recent experience is confined to VHF is a less than efficient strategy, and, quite frankly, unfair on the staff concerned.
Merchant Navy Radio Officers were not allowed to be in charge of a ships radio station until they had served a minimum period with a senior colleague. Coast Radio Station staff were subject to the same requirements - new operators were closely supervised, and more experienced staff were always on hand during any neophyte's learning phase.
Now, I am not in any way criticising the professionalism of the new ops staff - however, I have to ask what level of training have they received? Have they sought and received advice/training from previous Coast Station Staff? To my knowledge, there is only one location where any kind of handover arrangement is/was in place. I understand that the Melbourne station operators are receiving assistance from their colleagues at VIM. Hats off to the Victorian authorities for taking this eminently sensible step.
Is this arrangement being duplicated in other states? Informal advice is no.
Positives
To give the new network designers their due, station distribution seems satisfactory - indeed, the siting of a station at Port Hedland may well provide better coverage than the previous network - there is a lot of ocean between Darwin and Perth.....
Conclusion
In consideration of the shortcomings identified in this brief analysis, I can only conclude that the replacement Australian Coast Radio network will not maintain the level of service of its predecessor.
The efficiency of the SOLAS watch is seriously compromised by the use of scanning receivers, the lack of working channels must lead to excessive traffic on the distress and safety channels, and the utilisation of operators with a restricted experience base and (so it appears) little in the way of training will lead to operational difficulties.
Solutions?
The configuration of the network is such that rectification of the shortcomings outlined above is not an overly complex job. New working channels can easily be assigned - indeed, with the closure of Telstra's radphone service there are numerous duplex channels available for the new network. Moreover, many ships are already equipped with the channels in question (405, 602, 802) - that would simplify matters even more.
The scanning receiver problem can be easily overcome - there is a technical work around for this that would involve little real expense.
As to the operators - it would be a simple matter to delve into the wealth of talent and experience made available with the closure of the CRS. I could name at least a dozen CRS operators off the top of my head who would be most suitable to conduct mentoring of the new ops staff.
Time moves ever onward. The CRS has closed for ever.
It need not die in vain.
Any replacement network must provide an equivalent level of service, in real terms.
This is what the politicians so often like to tell us....
G.C. Dunstan
Densham & Associates P/L
20 July 2002