Report on the Spectrum Audit of the Band - 9 kHz to 28 000 kHz

Contents

1.	Terms of Reference
2.	Acknowledgements
3.	Executive Summary
4.	Introduction and Background
5.	Radio Wave Propagation Aspects
6.	Existing Records and Monitoring
7.	Services Within the Audit Frequency Range
8.	Proposed Future Uses
9.	Entries in the National Frequency Register
10.	References
	Annex 1 - Table of Allocations Users and Services
	Annex 2 - Chart Showing Percentage of Allocation per User Group
	Annex 3 - Further Information

1. Terms of Reference

1.1 The Radiocommunications Agency (RA) undertook to audit the bands 9 kHz to 28 000 kHz and 30 - 105 GHz with the following objectives:

i) to establish the extent of use of the radio spectrum in those frequency bands;

ii) to identify future requirements in those bands;

iii) to produce, by the end of 1994, a report for consideration by the RA Spectrum Policy Committee (Chairman Michael Goddard).

- Statement on the Late Publication of this Report -

The band 9 kHz to 28 000 kHz has not previously been subjected to an extensive audit and therefore an information gathering phase was commissioned at the inception phase of the work. This proved to be more onerous than had first been estimated and is the reasons for the delay in publishing this Report.

Back To Contents

2. Acknowledgments

2.1 We would like to express our thanks to all of those who contributed to this audit. We very much appreciated the time and trouble that so many individuals, industry and other government departments went to in order to help us identify the many uses that this frequency range supports. At the same time it enabled us to locate uses of parts of the frequency range that hitherto had been unknown.

Back To Contents

3. Executive Summary

3.1 The information presented in this Report contains the results of the audit of the frequency range 9 kHz to 28 000 kHz. For ease of presentation all of the frequencies within this Report, and within the associated tables, are in kHz.

3.2 The frequency range subject to this audit has been at the forefront of communications for about a century and therefore it is not surprising to find that many past recorded uses are now untraceable.

3.3 The search of the National Frequency Register¹ (NFR) covering the period 1994-1995 over the frequency range of interest here indicates that there is a large discrepancy between the recorded use and the apparent actual use, a much greater effort than has been expended here will be needed if the actual current use is to be reflected in the NFR.

3.4 Propagation characteristics associated with this frequency range, commonly referred to as the High Frequency (HF) band, are somewhat complex and reliant on a number of variable factors. The band is traditionally used for long distance World-wide radio communications and in order to accommodate the vagaries of the propagation characteristics prevailing at the time of transmission a number of discreet operating frequencies, across the entire HF band, are required for each individual service, a detailed explanation of the radio wave propagation aspects is given in Chapter 5. These same effects can also be troublesome in terms of unwanted interference from the World-wide use of the band and hence international coordination is necessary to protect the wanted service and minimise interference.

3.5 The RA Baldock Monitoring Station facilities have been used to ascertain the validity of some of the entries in the NFR, and, in conjunction with other monitoring facilities in Holland, it has been possible to verify a limited number of assignments over a small sample range of frequencies. Monitoring is a time consuming task, it is estimated that 3 to 4 years would be needed to produce more meaningful results across the frequency range audited here.

3.6 There is a wide range of services using this part of the spectrum in the UK and given the vagaries of radiowave propagation it remains a popular frequency range with many of its users. Military applications show little sign of abatement as does the international use for marine and aeronautical services. Members of the Radio Society of Great Britain make great to use of the band and carry out research within a number of sub-bands across the range; they also seek to extend their research into the Very Low Frequency (VLF) range.

3.7 Although alternative means of radio broadcasting to other counties are now available, such as by satellites direct to the listener or via a satellite link to a conventional terrestrial transmitter located within the desired service area, the band remains a growth area for the BBC World Service. There are plans to adopt T-DAB techniques within the HF bands for broadcasting services to improve reception, however, a number of International Telecommunication Union (ITU) World Radio Conferences have been unable to agree plans for the band and as a result many services operate outside of any internationally adopted plan.

3.8 Great use is made of this part of the spectrum for short range low power applications, there seems to be no end to the varied and novel uses gaining popularity with the end users. From electronic tagging, searching for underground pipes, specialised short range communications to opening garage doors; the diverse use is always expanding.

3.9 Chapter 4 gives general background information, Chapter 5 gives some general details on the propagation aspect of the band and Chapter 6 is devoted to what has been found in existing records. Chapter 7 contains details on the major uses of the band that have been identified during the audit and Chapter 8 covers proposed new applications where these have been identified. Chapter 9 covers those entries found in the NFR. Annex 1 contains details on current allocations and users within the review range and Annex 2 provides an estimate of the percentage of frequency allocation per user group within the review range.

3.10 The following further work has been identified during this audit:

1. To enable this range of frequencies to support new and innovative applications it is necessary to identify and eliminate those registered uses which appear to be currently unused. It is recognised that this would require a heavy commitment in terms of resources, time and effort.

2. The RA Monitoring facilities at Baldock could be used in conjunction with other sources to produce a clearer picture of the actual use of this frequency range. The way in which such monitoring is done should also be reviewed using the Dutch model as an example.

3. Pirate broadcasting has been observed during the limited monitoring exercises on aeronautical en-route frequencies and this should be investigated further.

4. Those involved in this audit consider that it has only scratched the surface and much more effort would be required to enhance the picture further.

Back To Contents

4. Introduction and Background

4.1 With the completion of the three independent reviews of the radio spectrum, together covering the range 28 000 kHz to 30 GHz, it is seen as central to the spectrum management role of the RA to complete the picture of spectrum usage of the portion of the spectrum not already covered. Internal audits of the remaining bands below 28 000 kHz and above 30 GHz were instigated; the subject of this Report is the lower band covering the frequency range 9 kHz to 28 000 kHz.

4.2 The range of spectrum covered here has not previously been subject to any formal review and therefore considerable time was spent in gathering data on which to base the Report. A wide a sample of users as possible has been included in this audit and the work included specific band monitoring conducted by the RA Baldock Monitoring Station. However, it has to be recorded that the response to the RA invitation to contribute to the audit has been disappointing.

4.3 Contained within the radio spectrum under review here are to be found the primitive beginnings of wireless communications. It is therefore no surprise to find that within the existing RA records there exists many examples of untraceable uses of this portion of the radio spectrum. Taking the entries in the NFR as an example, there appears to be a very large discrepancy between what is recorded as being in-use and what has been found in the various searches through the published records. During the limited time span of the audit a monitoring exercise, concentrating on specific parts of the band, has confirmed the potential for discrepancy within the constraints mentioned in Chapter 5 on radio wave propagation aspects but does not explain fully the many thousands of unaccountable entries in the NFR.

4.4 It should be noted here that all of those concerned with this audit felt that with the imposed time restraints it was only feasible to scratch the surface of this low frequency time capsule. A realistic time scale to produce a more definitive analysis, including a comprehensive programme of monitoring, would be in the order of 3 to 4 years.

Back To Contents

5 Radio Wave Propagation Aspects

5.1 Radio wave propagation aspects associated with the band below 28 MHz are somewhat complex and in the past have enabled communication networks to be developed on a World-wide scale.

5.2 There are two independent modes of radio wave propagation associated with frequencies below 28 000 kHz, ground (surface) wave and skywave. The groundwave component arises from currents induced in the ground and travels along the Earth's surface whereas the skywave component propagates through space.

5.3 Because the tangential component of the electric field cannot exist along the ground surface, vertical polarisation is used where propagation via groundwave is required. At frequencies, below about 500 kHz the groundwave mode of propagation can be used to communicate reliably over long distances. However, attenuation above 10 000 kHz is so high that ground wave propagation is of little practical value. The groundwave loses energy as a result of dispersion along the Earth's surface and energy dissipated in the Earth. These losses vary directly with frequency and the permittivity of the Earth's surface over which the wave front traverses.

5.4 The skywave mode of propagation is generally used at higher frequencies and its application to long distance communications is influenced by a number of factors. The skywave component is subjected to attenuation by free space loss, however, that portion of the energy that travels upwards enters an ionised layer known as the ionosphere, the existence of which becomes significant above approximately 50 km above the Earth's surface. In this ionised region the path of the wave is altered by refraction, the degree of refraction depends on the electron density and frequency of the wave. The ionisation density (electron density) in the ionosphere varies depending on sunspot activity, time of year and daytime to night-time. The sunspot activity varies over a 11 year cycle but can vary considerably within a cycle, even on a day-to-day basis and is caused by 'solar flares' which not only increase the ionisation density of the ionosphere but also causes large variations in the Earth's magnetic field, these variations in the magnetic field often precede changes in the ionosphere and can therefore provide a very useful warning of an ionospheric disturbance.

5.5 The ionosphere is defined as part of the upper atmosphere where sufficient ionisation can exist to affect the propagation of radio waves in the frequency range 1 to 30 000 kHz. The ionosphere exists between 50 km and several Earth radii above the surface of the Earth and is divided into a number of regions. Peak electron density usually occurs in the F Region, some 140 km above the surface of the Earth. The F Region is divided into the F₁ layer and the F₂ layer, both of which are produced by solar extreme ultra violet light (EUV). Below the F Region is the E Region at a somewhat lower height of between 90 km to approximately 140 km above the surface of the Earth. This Region is produced by solar soft X rays which contains both the normal E layer and patches of sporadic E (E_s). Sporadic E, can, on rare occasions, give rise to unwanted long distance communications at frequencies up to 100 000 kHz, creating havoc with planned line-of-sight services. There is a further region known as the D region which exists in the height interval 50 km to 90 km above the surface of the Earth.

5.6 Ionospheric radio propagation is characterised by amplitude fading, ray penetration, absorption etc., making it unreliable for certain uses. Most of the move away from HF long distance skywave communications has been to satellite which can provide a reliable World-wide service. However, groundwave propagation is still used extensively at medium frequencies (MF) for national broadcasting and at low frequencies (LF) for long distance communications including broadcasting in the high frequency end of the LF band and for subterranean communications at the low frequency end of the band.

5.7 Prediction of frequencies for use at HF are done on a World-wide basis, data is sent to a number of 'World data centres' who in turn issue monthly predictions of maximum usable frequency (MUF) this is based on a number of complex factors but is usually defined as M (3000) which is the MUF for a 3000 km single hop link.

5.8 In summary, the band below 28 000 kHz is subject to a critical division between the influence of the two modes of propagation, groundwave at frequencies below about 500 kHz and skywave above about 1 000 kHz. Both modes being further complicated by the vagaries of the permittivity of the Earth's conducting layer influencing groundwave propagation and the ionosphere dominating the skywave component. These two modes have been exploited to the full over a number of decades and with this intense use came unwanted interference on a World-wide basis.

5.9 One other mode of propagation, the induction field, is also exploited within this frequency range for near field (short range) communications which has enabled innovative development of a wide variety of short range devices.

Back To Contents

6. Existing Records and Monitoring

6.1 During the work of this Review it has been necessary to seek evidence from a variety of sources as to whom is using what and where. Such records that are available have seemingly not been maintained and at best appear to be unreliable.

6.2 The number of assignments recorded as being in use in the NFR is currently in the order of 17,000 with a fairly even spread across the whole band 9 kHz to 28 000kHz. The ITU International Frequency List² (IFL), March 1994 edition, contains some 5,143 assignments as being registered in use in the UK.

6.3 Because of the apparent large discrepancy between the national and international records attention was focused on records of monitoring carried out in the band being audited and here, due mainly to the vagaries of propagation, the records are at best unreliable. A previous database³ developed by the RA Baldock Monitoring facility over a number of years contained some 5,520 entries but it was evident that this did not reflect the current situation. Results of recent monitoring carried out over a small portion of the band during this review by Baldock confirmed only some 824 operational uses within the UK, excluding MF broadcasting. There are many problems in producing reliable monitoring results such as the particular frequency assignment may not be operational at the time it was monitored, particularly relevant when a service employs multiple frequency assignments. Identifying emissions emanating from within the UK can be difficult due to the unique propagation characteristics associated with this band. Its recognised that precise monitoring in this band is time consuming and costly and that international co-operation in monitoring this band is seen as essential. For example, the Dutch Monitoring Service has a continuous monitoring programme in operation which in some respects is better placed to monitor what occurs within the UK and we have taken advantage of the results⁴ of this service in this review.

Back To Contents

7. Services Within the Audit Frequency Range

7.1 Government Services

7.1.1 Military services can be found throughout the band 9 kHz to 28 000 kHz, they occupy an estimated 34% of the available spectrum. An increasing need is seen for the use of assignments particularly for the Navy where it is already common practice to divide each 6 kHz channel into two independent 3 kHz channels, using single sideband emissions. Widespread use of data has replaced conventional speech for many of the traditional uses and techniques such as packet transmissions are now common place.

7.1.2 Major incidences such as the Gulf War and the later crisis in Bosnia and Croatia have shown that the bands below 28 000 kHz still have an important place in military communications.

7.1.3 Because of the variable nature of the skywave propagation mode, mentioned in Section 4, it is vital that the military continue to have access to sub-bands evenly spaced across the whole range 9 kHz to 28 000 kHz.

7.2 Broadcasting Services

7.2.1 BBC World Services

7.2.2 The BBC World Service⁵ is transmitted, either directly or via relays, in English to nearly every corner of the World and is also provided in some 38 different languages to Europe, Africa and the Middle East, Asia and to Latin America. The service has access to about 7 % of the available spectrum within the audit range.

7.2.3 All of the assignments are transmitted via Rampisham, Skelton and Wooferton using a maximum carrier power of 500 kW in any one azimuth. Use of some assignments on a number of azimuths simultaneously can produce carrier powers on any one assignment of up to 2000 kW.

7.2.4 Additionally, the Service is carried by 648 kHz via the Orfordness transmitter and at out of broadcasting hours via the 198 kHz long wave service from Droitwich. A number of UK local radio services carry the BBC World Service overnight when their own service closes down. The service is also relayed in Europe on the Astra 1B satellite and some services are carried in English on the Intelsat 601 and Asiasat 1 satellites.

7.2.5 An interesting future development in the HF broadcasting bands is the possible introduction of digital modulation in a 10 kHz channel, as currently used in T-DAB, the rationale being that multipath propagation aids reception.

7.2.6 The following table gives a list of the bands currently used for the World Service, all of the bands shown in Table 1 are within the ITU Article 17 Broadcasting Bands⁶:

Table 1: Use of the Broadcasting Bands

7.2.7 Frequencies listed in Table 2 are also used by the BBC for their World Service. Although these are operated outside of the current Article 17 Bands they are subject to RR 342.

Table 2: Frequencies not Covered by the Current Article 17 Procedures

7.2.8 The BBC have future plans for using those band allocations agreed at WARC79 and WARC92, these are listed in the following table

Table 3: WARC79/92 Band Allocations

7.2.9 LF and MF Radio Broadcasting

7.2.10 The BBC provides its national radio programmes⁷, Radio 4 and Radio 5 and a number of its local radio services, using frequencies within the LF and MF radio bands. These currently occupy some 1.8 % of the spectrum within the audit range. With the advent of the new digital audio broadcasting service, and a general migration to VHF, there has been a slow decline in the use of this range of frequencies for BBC services.

7.2.11 The Radio Authority is still developing independent national and local commercial radio services⁸ within the audit range. Currently these services utilise some 2.0% of the available spectrum. Further commercial services will be accommodated on frequencies released by the BBC as and when required.

7.3 National Air Traffic Services

7.3.1 National Air Traffic Services (NATS) is responsible for all civil aeronautical communications and radionavigation facilities within UK air-space, it also has joint responsibility with the Ministry of Defence (MoD) for some military services.

It is estimated that UK civil aeronautical services occupy some 8 % of the available spectrum in the band under review which excludes aeronautical mobile (OR) and test and development use.

7.3.2 A number of thunderstorm sensors, airborne

and ground based are located around the 9 kHz portion of the band. The band 9 kHz to below 200 kHz is mainly used for navigation systems such as Decca Navigator, Omega and Loran. Aeronautical beacons of the non-directional type are situated in the bands 255 to 1 606.5 kHz. Aeronautical mobile communications systems are located in a number of sub-bands within the range 2 850 kHz to 22 000 kHz.

7.3.3 A joint arrangement exists between the UK and Republic of Ireland where the UK has use of some 26 assignments located in the Republic for forward communications with aircraft operating across the Atlantic routes, these operate in the range 2 800 kHz to 17 970 kHz. There are also fixed service systems operating between the UK and Iceland within the range 2 194 kHz and 14 990 kHz.

Table 4: Summary of the Bands Used by International Aviation

7.3.4 Two other essential services, H M Coastgaurd which has two assignments at 20 locations within the UK and the Royal National Lifeboat Institute which also has two assignments at 170 locations around the UK, are covered by NATS service planning.

7.4. Radio Society of Great Britain

7.4.1 There are at present some 63,000 full licensed amateurs and about 2,500 novice licensed users within the four licence categories in the UK. Together they have access to about 5.9 % of the available spectrum within the range 9 kHz to 28 000 kHz. The sub-bands allocated to the Amateur service are spread across the Review range and provide for self-training, intercommunication and technical investigations.

7.4.2 Specific Comments on the Sub-Bands

7.4.3 1 810-2 000 kHz

7.4.4 This sub-band is currently the lowest allocated to the Amateur service in the UK. Its propagation characteristics allow short range communications during daylight hours and medium to long range during the night.

7.4.5 3 500-3 800 kHz

7.4.6 This allocation is used extensively for communication over distances of up to 500 km during hours of daylight and for distances of up to and beyond 2,000 km at night. It is one of the bands which is used for emergency communications in times of natural disasters under the provision of ITU Resolution 640.

7.4.7 7 000-7 100 kHz

7.4.8 This primary allocation carries heavy traffic 24 hours each day. During the hours of daylight this band carries the bulk of amateur skywave communication over distances of less than 1,300 km. During the winter months and periods of low solar activity it supports the majority of amateur intercontinental communication during the hours of darkness.

7.4.9 10 100-10 150 kHz

7.4.10 The sub-band is relatively new to the Amateur service and is the only high frequency (HF) allocation on a secondary basis and consequently care has been taken in using the band to fully protect the fixed service primary allocation.

7.4.11 14 000-14 350 kHz

7.4.12 This sub-band is the most popular amateur allocation for international communications. It carries an ever increasing load of both carrier wave (CW) and voice traffic but it is difficult to accommodate the newer digital modes within the sub-band.

7.4.13 18 068-18 168 kHz

7.4.14 This is used by amateurs wishing to avoid the congestion in the 14 000 kHz sub-band. It provides the necessary flexibility in selecting the prime operating frequency for a given path.

7.4.15 21 000 - 21 450 kHz

7.4.16 This band suffers from congestion during hours of daylight when the MUF exceeds 21 000 kHz.

7.4.17 24 890 - 24 990 kHz

7.4.18 This allocation provides an alternative to the 21 000 kHz sub-band when the MUF falls below 28 000 kHz

7.4 19 Future developments

7.4.20 There are some two million licensed amateur radio stations World-wide and this number increases at the rate of about 7 % per year, the number of licensed amateurs is expected to double by the turn of the century. The number and variety of modes of emission used by amateurs are also expanding creating greater demands for space by the users of established modes such as single side band (SSB) and continuous wave (CW). Spectrum efficient modes such as SSB, CW and radio tele type (RTTY) have been in widespread use since the 1950s.

7.4.21 New Allocations around 5 000 kHz

7.4.22 It was accepted in principle at WARC 1979 that, like other HF radio services, the amateur service should have access to a family of frequency bands so that communications can be maintained as propagation conditions change. New exclusive allocations have been added in the vicinity of 18 000 kHz and 25 000 kHz and a new allocation with secondary status was added at 10 000 kHz to bridge the gap between bands. However, the existing gap between the 3 000 kHz band and 7 000 kHz band should be filled with an additional allocation around 5 000 kHz.

7.4.23 Return to 300 kHz bandwidth at 7 000 kHz

7.4.24 The allocation at 7 000 kHz was reduced from 300 kHz to 100 kHz prior to World War 2 in ITU Region 1. The RSGB consider that this should now be put back to 300 kHz in line with ITU Region 2. This is to ease current congestion in the present allocation.

7.4.25 Very Low Frequency (VLF)

7.4.26 As to the future the RSGB would like access to a very low frequency assignment (VLF) since there is considerable interest in propagation and antenna experimentation by individual amateurs in this region.

7.5. Maritime Services

7.5.1 A number of changes were made to the Maritime Mobile bands at the ITU WARC Mob-87 Conference and these came into effect on 1 July 1991. The main changes included a reduction in channel spacing from 3.1 kHz to 3 kHz for all duplex and simplex radiotelephony and all assigned carrier frequencies were made integer kHz. The number of channels assigned to Paired Narrow-Band Direct Printing (NBDP) and Non-Paired Direct Printing (NBDP) was increased, there was also an increase in the number of channels to Digital Selective Calling (DSC). Two new bands were opened at 18 000-19 000 kHz and 25 000-26 000 kHz which will be used for telephony, wide-band telephony, wide-band telegraphy, NBDP and DSC. Spot frequencies in the 415-526.5 kHz and 1606.5-4000 kHz bands have been assigned to DGPS coastal transmitting stations in the UK. It is estimated that civil maritime services occupy some 27 % of the available spectrum in the range 9 kHz to 28 000 kHz.

7.5.2 Table 5 - Channelling Arrangements For Maritime Services

7.5.3 British Telecommunications

7.5.4 The are some 17 coast stations from which BT operate services to shipping within the band reviewed here, they currently occupy some 9.5 % of the available spectrum. The services offered include voice, paging, selective calling, data and correction for DGPS. A listening watch is also provided on international distress frequencies at selected sites.

7.5.6 Short Range Applications

7.5.7 A wide variety of devices providing short range communications, data exchange, metal detecting equipment, remote operating devices, inductive loop systems etc., are accommodated within the frequency range. They occupy an estimated 1% of the spectrum of interest here and are contained in the 9- 315 kHz sub-band, some broadcasting induction loop systems operate in the 526.5-1 606.5 kHz band, commonly referred to as the medium frequency (MF) broadcasting band.

Back To Contents

8. Proposed Future Uses

8.1.1 The theme that has come across throughout the work has been that there is in general a diminishing requirement within the United Kingdom for the use of this band for civil World-wide communications. There now exist attractive alternative solutions to the problem such as satellites and through the use of fibre optical cables.

8.1.2 There may also be forthcoming evidence in the number of cancellations by organisations such as BT, where technology has largely replaced the need for low frequency long distance links. However, single hop links to connect BT telephone installations in remote mountainous areas of Scotland and Wales may be on the increase, but even here the higher VHF bands are seen as being more attractive.

8.1.3 Evidence from Cable and Wireless indicates that whist the band is not used by them in the UK they currently expect to continue to increase their use of it overseas.

8.1.4 Where the band is used internationally there is evidence to indicate that new services are being planned. The Civil Aviation Authority (CAA) with the International Civil Aviation Organisation (ICAO) are planning extra services in the form of information to aviators using digital encoding techniques.

8.1.5 Broadcasters are studying the feasibility of employing T-DAB technology to the HF Broadcasting Bands to make use of the additive nature of multipath effects enhancing reception in these bands.

8.1.6 There is no foreseen diminishing use by the military within this frequency range in the foreseeable future. The recent World conflicts have demonstrated the robust nature of military communications here, and, with future digital applications, the 9-28 000 kHz frequency range is seen as an essential element in military communications.

8.1.7 There are currently some 63,000 full licensed amateur radio users in the UK within the frequency range and this figure increases by some 7% per year. A variety of transmission modes are being investigated and some new sub-bands are being sought to promote technical investigations. A low frequency assignment in the 71.6-74.4 kHz band is being considered by the RA to enable radio wave propagation and antenna characteristics to be investigated at this end of the radio spectrum.

8.1.8 Another growth area is in the application of short range devices, diverse applications such as underground pipe location, underground and underwater communications, security tagging, restricted broadcasting services etc., are seemingly endless.

Back To Contents

9. Entries in the National Frequency Register

9.1 This audit has found an estimated 17,000 assignments registered as being in-use in the NFR within the range 9 kHz to 28 000 kHz, of these some 5,600 entries have been traced through the various references, the main ones being the ITU International Frequency List - March 1995 edition and the Dutch Monitoring Report 1994 edition. Ignoring the broadcasting band, 531-1 602 kHz, the limited monitoring programme has positively identified only 824 assignments and, therefore, some 11, 400 assignments are unaccounted for.

Back To Contents

10. References

1. National Frequency Register maintained by the RA and containing all civil registered uses of the radio spectrum in the UK.

2. ITU International Frequency List - March 1994.

3. Results of monitoring conducted by the RA at its Baldock monitoring facility.

4. Monitoring information from the Dutch Administration - HMS M9509, HMS M9508, HMS M9523, HMS M9524 covering the period May 1995 to September 1995.

5. Information on the BBC World service supplied by the BBC and additional material obtained from their published service schedules.

6. ITU Radio Regulations - Geneva 1994.

7. BBC pocket guide to radio services - 1994.

8. Radio Authority guide to services - 1994.

Back To Contents

ANNEX 1 - Table of Current Allocations and Users in the Range 9 kHz to 28 000 kHz

All frequencies in the table are in kHz