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8.33kHz spacing on the VHF Airband
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The introduction (a term we should not take too seriously at present) of the new 8.33kHz steps for the VHF airband has caused and continues to do so considerable concern amongst many listeners with the fear their existing receivers are going to become redundant in the near future.
Fear not !
Much of what has been written in the aviation and radio press has been a little misleading, or at least resulted in many being mislead. I hope the following may alleviate some of your fears and also provide a little additional information to the project.
Key facts and background
- The 8.33kHz channel spacing does not effect any UHF allocations
- September 1994/March 1995: In order to increase channel capacity for regions experiencing severe VHF frequency spectrum congestion it was decided at the ICAO Special EUR Regional Meeting in Vienna and the Special Communications/Operations Divisional Meeting in Montreal that the VHF communications spectrum be split from 25kHz to 8.33kHz.
- November 1996: The plan for 8.33kHz implementation within the EUR regions was endorsed by the European Air Navigation Planning Group with the Carriage and operation of 8.33kHz capable avionics will become mandatory in the ICAO EUR Region on the 1st January 1999 for flights above FL245 generally and FL195 over France. Except where exemptions apply only aircraft with 8.33kHz capable avionics will be allowed to operate in the EUR region above FL245 or FL195 in France.
- June 1998: The EUROCONTROL ATM/CNS Consultation Group (ACG) unanimously concluded that the deadline of 1 January 1999 for the implementation of 8.33 kHz channel spacing in the ICAO EUR region was no longer maintainable due to the low percentage of aircraft projected to be 8.33 kHz capable on that date. This conclusion was reached after assessing the retrofit information provided by aircraft operators, directly to EUROCONTROL and/or via IATA and ATA.
- July 1998: The EUROCONTROL ATM/CNS Consultation Group (ACG) agreed to delay the implementation of 8.33kHz channel spacing in the ICAU EUR region by 9 months. Accordingly, the new date of mandatory carriage of 8.33kHz capable radio equipment is 7 October 1999. This deadline will not be extended and non-equipped flights will have to face severe restrictions following the delay period.
- Those European States that will initially implement the new channel spacing are Austria, Belgium, France Germany, Luxembourg, Netherlands & Switzerland.
Although initially not all the States (countries) in the EUR region are implementing 8.33kHz spacing the mandatory carriage of 8.33kHz capable avionics above FL245 and FL195 in France applies to the whole of the ICAO EUR region. Normally no 25kHz back up frequency will be available in sectors using 8.33kHz.
- The U.K. is not planning to introduce 8.33kHz channel spacing before the year 2000 and in addition any allocations within the U.K. are likely to be few and far between. In the Plan for the 8.33 kHz Channel Spacing Implementation in Europe (Edition 2.0, December 1996) document only one London ATCC sector is identified as one within which 8.33 kHz channel spacing would possibly be implemented
Whilst no connection has been inferred this could be in connection with the new ATCC centre at Swanwick (replacing West Drayton) which is running some considerable way behind schedule.
The mandatory carriage of 8.33kHz equipment means that any aircraft without such equipment will not be allowed to operate above FL245 (FL195 in France) in the EUR region. This would mean that any flights arriving in the EUR region from adjoining regions without 8.33kHz spacing have to be re-routed or descended to lower levels. Quite a headache for ATC I should think !
How will/does ATC know if an aircraft is 8.33kHz equipped ?
As from the 1st October 1998 all Flight Plans will contain a field whereby the pilot will be required to state if the aircraft is 8.33kHz equipped or not. This will allow the organisations involved the opportunity to assess the progress made by airlines and operators with regard to 8.33kHz capability and take a decision as to whether the project can proceed as planned.
What frequencies will be used and how will they be referred to ?
It would appear that initially all 8.33kHz allocations are planned to be between 132.000 - 134.800MHz with any current 25kHz spaced allocations between these frequencies moved. This is not definitive however and some allocations outside these limits may be made.
The phrase "Channel" will be used to identify 8.33kHz spaced frequencies rather than the frequency. The table below shows show the spectrum would be split together with corresponding channel numbers.
| Frequency MHz
| Spacing kHz
| 25kHz Spaced Frequency
| 8.33kHz Channel
(Not frequency)
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| 132.0000
| 25
| 132.000
|
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| 132.0000
| 8.33
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| 132.005
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| 132.0083
| 8.33
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| 132.010
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| 132.0166
| 8.33
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| 132.015
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| 132.0250
| 25
| 132.025
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| 132.0250
| 8.33
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| 132.030
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| 132.0333
| 8.33
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| 132.035
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| 132.0416
| 8.33
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| 132.040
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| 132.0500
| 25
| 132.050
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| 132.0500
| 8.33
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| 132.055
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| 132.0583
| 8.33
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| 132.060
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| 132.0666
| 8.33
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| 132.065
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| 132.0750
| 25
| 132.075
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To instruct a flight to change to a currently assigned 25kHz spaced frequency "Flight 123 contact London 132.05" would be the phraseology used.
To instruct Flight 123 to change to 132.0083MHz the phraseology used will be "Flight 123 contact London Channel 132.010 ("London Channel Wun tree too decimal zero one zero") rather than "Flight 123 contact London 132.0083".
Exemptions
States in the area of Mandatory Carriage may also grant exceptions within their area of responsibility. An exemption will allow flights of non 8.33kHz equipped aircraft within that portion of the area of Mandatory Carriage. There will be two types of exemptions:
- Unconditional: All flights of non equipped 8.33kHz aircraft are permitted.
- Conditional: Only clearly specified categories of flights are permitted.
Further Information
For those with Internet access there are several Web sites of interest. The Eurocontrol 8.33kHz site is of particular interest as it is possible to download two publications, namely:
Other Sites:
On to more important things !
Is my scanner/receiver or one I am considering purchasing going to be obsolete ?
First thing to really remember is that even when any 8.33kHz frequencies are finally introduced these are going to be few and far between. They will be for sectors in controlled airspace above FL245 (FL195 in France). It is my guess that any allocations in the UK will occur in the South of the country in sectors around/in the London TMA. This still leaves the vast majority of allocations for FL245 and above remaining at the current 25kHz spacing and there will be no changes (8.33kHz allocations) to local A/G, Ground, Tower, Radar, Approach/Departures or for sectors below FL245.
The AR8200 is/was the first handheld receiver that allows any 8.33kHz frequencies to be implemented correctly. Taking a new allocation of 132.0083Mhz as an example it would not be possible on the majority of receivers to enter this frequency exactly via the keypad. What frequency will be displayed after hitting the Enter key will vary depending on the increment step chosen or that your receiver defaults to on the VHF airband.
For receivers with programmable increment steps then it should be possible to enter a frequency close enough that will not cause any problems. The display might be slightly off but the reception will not be noticeably affected. The filter used for AM on many receivers is often around 12kHz filter (+/-6kHz) and with 1kHz tuning steps being available on many receivers you would able to enter 132.0080Mhz - certainly close enough not to cause any problems in view of the filter width used. With some receivers including the AR8000, MVT-9000 & DJ-X10 you have 50Hz steps available which would allow 132.00835 !
With 1kHz tuning steps available frequencies accepted could be:
132.0000, 132.0010, 132.0020, 132.0030, 132.0040, 132.0050, 132.0060, 132.0070,
132.0080, 132.0090, 132.0100, 132.0110, 132.0120, 132.0130, 132.0140, 132.0150,
132.0160, 132.0170, 132.0180, 132.0190 and so on
With only 5Khz or 12.5kHz available tuning steps frequencies accepted would be:
132.0000, 132.0050, 132.0100, 132.0125, 132.0150, 132.0200, 132.0250, 132.0300,
132.0350, 132.0375, 132.0400, 132.0450, 132.0500, 132.0550, 132.0600, 132.0625,
132.0650, 132.0700, 132.0750, 132.0800, 132.0850, 132.0875, 132.0900, 132.0950,
132.1000 and so on
If you do have a receiver with programmable step sizes try a little experiment:
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Select your local VOLMET or ATIS frequency for a continuous transmission - select 1kHz and see how far up/down you can go before the signal becomes unreadable.
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The further away you go the reception will deteriorate as it reaches the extremities of the filter bandwidth but you might be surprised as to how many kHz you can move away from the centre frequency before the transmission becomes unreadable.
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Even if the smallest step size is only 5kHz you will probably find you can still go at least one increment (that's 5kHz) up or down and still receive the transmission !
On receivers where 25kHz channel spacing is the default and it is not possible to change then you will probably find that on pressing the enter key you would get an error message or the frequency will be rounded down to the nearest 25kHz spaced frequency and this would not be close enough to receive the transmission of the desired the 8.33kHz spaced frequency.
Frequencies available with 25kHz spacing would be:
132.0000, 132.0250, 132.0500, 132.0750, 132.01000
So, as a Rule of Thumb:
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Receivers/Scanners with default (cannot be changed) steps sizes of 25kHz on the VHF airband will not receive any transmissions from 8.33kHz spaced frequencies (when & if they ever appear).
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Receivers/Scanners with programmable increment steps, especially those of 1kHz or smaller are not going to have any problems in receiving transmissions from 8.33kHz spaced frequencies (when and if they ever appear).
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