Illawarra television overspill into Sydney licence area. Engineering assessment of Southern NSW broadcasters submission of 17 March 2006

Transcription

1 Illawarra television overspill into Sydney licence area Engineering assessment of Southern NSW broadcasters submission of 17 March 2006 Australian Communications and Media Authority Canberra

2 Background The Australian Communications and Media Authority (ACMA) received a formal complaint dated 18 July 2005 that the Southern New South Wales commercial television licensees were in breach of their licence conditions evidenced by the very significant and continuing overspill of [their] signals into the Sydney TV1 licence area from the broadcast site on Knights Hill serving the Illawarra area. The commercial television broadcasting licensees in the Southern NSW TV1 licence area who broadcast from Knights Hill are WIN Television NSW Pty Limited (WIN), Prime Television (Southern) Pty Limited (CBN-Prime) and Australian Capital Television Pty Limited (CTC-Southern Cross) (collectively the Southern NSW broadcasters). The complainant submitted that the reasons signals from Knights Hill could be received in the Sydney TV1 licence area included: the strength of the signals; the antenna height and patterns of the Knights Hill transmissions; and the lower frequencies of the digital services. ACMA wrote to the Southern NSW broadcasters on 9 September 2005 requesting details of the operating conditions of their analog and digital television services so that ACMA could assess whether the services were operating as per their Licence Area Plan (LAP) and Digital Channel Plan (DCP) specifications. The then Broadcast Planning Branch (now Allocations Branch) assessed the details submitted by the Southern NSW broadcasters and predicted the coverage of the Illawarra analog and digital television services based on these details. A preliminary report was prepared in November 2005 to collate the technical information provided by the licensees and summarise ACMA s assessment of the technical information and the coverage of the Illawarra services within both the Southern NSW TV1 and Sydney TV1 licence areas. The preliminary report noted that the WIN analog service from Knights Hill has significantly poorer coverage than the other analog services because of its lower antenna height. The DCP technical specifications for all the national and commercial digital services at Knights Hill are substantially the same allowing WIN to provide equivalent digital coverage to the other broadcasters but better coverage than its analog service. The preliminary report concluded that the Illawarra commercial analog and digital television services are substantially operating as per their LAP and DCP technical specifications and that the predicted coverage of the commercial digital television services from Knights Hill indicate most of Western Sydney, Sutherland Shire, Southern Sydney and north western suburbs would receive better than a rural grade of service with many areas receiving an urban grade of service. These areas fall outside the Southern NSW TV1 licence area. The above conclusions were supported by ACMA field strength measurements in Sydney of the Illawarra services, made during a survey of the coverage of the Sydney digital television services. Australian Communications and Media Authority 1

3 Based on the grade of service currently being received by areas outside the Southern NSW TV1 licence area as discussed in the Preliminary Engineering Report, ACMA formed the preliminary view that the Southern NSW Broadcasters were providing a commercial television broadcasting service outside of their designated licence area. ACMA wrote to the Southern NSW broadcasters on 13 December 2005 seeking comment and further submissions in relation to: 1. the finding of the Preliminary Engineering Report regarding television transmission overspill into the Sydney TV1 licence area; and 2. the applicability of any of the exceptions set out at subclause 7(2A) of Schedule 2 to the BSA. ACMA s letter suggested that submissions may also address the impact of steps that might be taken to mitigate the overspill into the Sydney TV1 license area, such as whether reducing or changing transmission would mean persons in the Southern NSW TV1 licence area would no longer receive adequate commercial TV services, or whether people in the Sydney TV1 licence area who are wholly dependent on Illawarra digital television transmissions might be deprived of an adequate commercial television broadcasting service. ACMA received a joint response from the Southern NSW broadcasters on 17 March This note is an assessment of the technical issues addressed in that submission. Assessment of Technical Issues in Broadcasters Submission The principle technical elements of the March 2006 joint submission from the Southern NSW broadcasters which relate to ACMA s consideration of whether the broadcasters are in breach of their licence conditions are that: the Southern NSW broadcasters need to operate their analog and digital television services with their current technical specifications to adequately serve their licence area; any change to their transmissions to effectively limit overspill into the Sydney TV1 licence area will adversely affect this reception; the Illawarra services were implemented in accordance with technical specifications determined by ACMA s predecessor the Australian Broadcasting Authority (ABA); ABA/ACMA planning for the Illawarra services would have been aware of the potential for overspill outside the licence area [and] accepted that this level of overspill was a necessary consequence of delivering an appropriate level of coverage within the Licence Area ; and any subsequent changes to the technical specifications will result in significant additional costs to broadcasters and viewers. Australian Communications and Media Authority 2

4 The submission also discussed a number of other technical issues which are not considered in depth in this assessment, being that: the Southern NSW TV1 licence area has evolved from a service/licence area for the Illawarra services that was planned such that new services such as the WIN service were designed to ensure overlap where possible, so that the maximum possible coverage was achieved ; and overspill is a common consequence of broadcast planning throughout Australia and there is significant overspill of Sydney commercial television services into the Illawarra/Wollongong area. Current Coverage The Southern NSW broadcasters submitted that they operate digital and analog transmitters at Knights Hill to service viewers within the Southern NSW TV1 licence area in the Illawarra/Wollongong area. This area includes significant population centres to the north and west of Wollongong, including communities adjacent to the Sydney TV1 licence area. While the current services provide adequate analog and digital television coverage to the majority of viewers in the area there are significant population centres in areas such as Helensburgh and Hilltop where reception is marginal and viewers are required to install specialist receiving equipment (ie mast head amplifiers). The broadcasters estimate more than 7000 viewers in these areas depend on the Knights Hill transmissions for their television reception. The November 2005 ACMA preliminary report supported this observation and stated that there are a number of population centres within the Southern NSW licence area around Hilltop and Colo Vale to the north-west and Helensburgh to the north-east which are unlikely to be well served by repeater services and may only have a marginal service from Knights Hill. The Southern NSW broadcasters conducted field survey measurements in these areas (Helensburgh, Colo Vale and Hilltop) to confirm the adequacy and quality of the services in these communities. The measurement results and photographs of the surveyed areas were included in the submission along with coverage predictions made with the EDX software package. Details of the field survey methodology were not included with the submission. In subsequent discussions the Southern NSW broadcasters have advised ACMA that the measurements were conducted by representatives of the three licensees on the 27 th and 28 th of February using a vehicle provided by Prime. Measurements were conducted using a Rohde and Schwarz EFL100 portable test receiver and a Hills Hunter FB antenna mounted at 10m. Rather than measuring all analog and digital television transmissions at each measurement site, measurements were generally made of only the WIN59 and CBN65 analog television services and CTC37 digital television service (at some sites measurements were also made of the CTC62 analog television service). As the WIN59 transmission comes from one tower, the CTC62 and CBN65 services come from a second tower and the WIN36, CTC37 and CBN38 digital television services come from a third tower, it can reasonably be assumed that the coverage of the CTC62 and CBN65 services and WIN36, CTC37 and CBN38 services will be very similar. Australian Communications and Media Authority 3

5 This assumption appears to be well supported by ACMA field survey measurements of the Illawarra services. The Southern NSW broadcasters claim that these results indicate: the service in the majority of these locations measured is close to minimum signal levels with many viewers going to some effort to ensure adequate signal quality. The results verify the accuracy of coverage prediction software (EDX) used by the Broadcasters to ascertain the quality of coverage in the licence area. While measurements were only made in the Helensburgh and Hilltop area the submission claims the software modelling highlights other areas that would be affected by a reduction of the ERP at Knights Hill. The specific areas identified being the high population density areas around Cordeaux Heights and Farmborough Heights and newly settled areas around west Hilltop. The submission also refers to an ACMA report of a field survey of the Wollongong digital television services. ACMA has published reports of field surveys of the Bowral/Mittagong and Wollongong analog and digital television services 1. These reports include measurements of the Illawarra (Knights Hill) services that were taken in parallel with measurements of the repeater services. Comments in the ACMA reports indicate that viewers in some areas within the expected coverage of the Bowral/Mittagong and Wollongong services are reliant on the Illawarra services and at some of these locations reception would only be adequate with mast head amplifiers. ACMA measurements in the Bowral/Mittagong area showed that Illawarra services, with mast head amplifiers, were the best option in some areas of Berrima, Mereworth, Mittagong and Yanderra within the expected Bowral/Mittagong coverage area and in some areas of Cordeaux Heights, Farmborough Heights and Kembla Heights within the expected Wollongong coverage area. ACMA measurements in Hilltop showed good Illawarra signal levels, as did measurements taken by the Southern NSW broadcasters. ACMA did not conduct measurements in the lower areas of western Hilltop where the broadcasters found very poor Illawarra reception. ACMA did not conduct measurements in the Helensburgh area during the Wollongong survey although unpublished measurements taken as part of the Sydney surveys show very poor Illawarra reception at two locations with much better reception from Sydney. Allocations Branch is satisfied that the Southern NSW broadcasters field survey was conducted in an appropriate manner. The measurements included in the submission are similar to ACMA measurements and support predictions by both the Southern NSW broadcasters and ACMA that indicate some areas within the Southern NSW TV1 licence area will be relying on marginal signal strengths from the Illawarra services. The submission estimates that more than 7000 viewers in these areas [where reception is marginal and viewers are required to install specialist receiving equipment] depend on the Knights Hill transmissions for their television reception but there is no evidence given for the basis for this estimate. 1 Australian Communications and Media Authority 4

6 Using the ChirPlus planning tool and 2001 Census data, Allocations Branch estimates viewers to the north of Knights Hill within the Southern NSW licence area have marginal 2 analog reception. ChirPlus estimates 6000 viewers in this area would have marginal digital reception. These estimates include viewers who may have better reception from the Bowral/Mittagong or Wollongong translators so the total number of viewers solely reliant on marginal Illawarra reception in this area may be closer to Population estimates like these are very difficult to make however in this case the Southern NSW broadcasters estimate of 7000 viewers with marginal reception appears to be reasonable. The field strength measurements, predictions and photographs provided by the Southern NSW broadcasters in their submission support their argument that there are significant population centres within the Southern NSW licence area to the north of Knights Hill which rely on marginal reception of the Illawarra analog and digital services. This argument is supported by ACMA field surveys in the Bowral/Mittagong and Wollongong areas. Effect of transmission change to restrict overspill The November 2005 ACMA preliminary report concluded that a 10 db reduction in ERP to the north for the Illawarra digital television services will reduce the predicted field strength in much of the Sydney licence area to less than a Suburban grade of service. Even so, many viewers would probably still receive a good quality of service. In their submission of 17 March 2006 the Southern NSW broadcasters agreed that their predictions indicated a 10 db reduction in ERP toward Sydney is necessary to materially reduce the overspill. The submission states that of the sites measured, the majority of these would fall below the planning guideline rural contour for digital and analogue services should ERP toward Sydney be reduced by 10 db and concludes that any reduction in signal toward Sydney will result in a reduction in quality or cessation of services for viewers in the licence area. The coverage predictions included in the submission and ACMA measurements and predictions support this conclusion. The quality of all viewers analog reception will be affected by any significant reduction in ERP (ie more than 1 or 2 db). As indicated in the submission, viewers with marginal reception may lose all reception. A 10 db reduction in ERP is likely to also lead to complaints from viewers with currently good or very good reception who will notice a reduction in picture quality with the picture becoming noisier. Allocations Branch predicts that a 10 db reduction in ERP to the north of the Illawarra analog television services could result in the reception of viewers falling below the rural grade field strength and viewers losing their current marginal analog reception. 2 Allocations estimate of viewers with marginal reception is those with a predicted field strength within 10 db below the expected rural grade field strength. Australian Communications and Media Authority 5

7 Digital reception is different in that the picture appears equally good whether there is just enough signal level for stable reception or very high signal levels with a large margin to failure. A 10 db reduction in ERP will cause viewers with marginal signal levels to lose all reception and currently good signal levels to become marginal with viewers experiencing an increase in occasional picture blockiness and signal drop-out. Unlike analog services though, there may be some viewers with high signal levels who would not notice any change in reception quality with a reduction in ERP. Allocations Branch predicts that a 10 db reduction in ERP to the north of the Illawarra digital television services could result in the reception of viewers falling below the rural grade field strength and viewers losing their current marginal digital reception. These population estimates do not include viewers who may have better reception options from the Wollongong and Bowral/Mittagong translators. Allocations Branch estimates that the population that could lose current marginal reception is probably between about 3000 and A further viewers could potentially have their currently adequate analog (and possibly digital) reception become marginal. Allocations Branch considers that there is sufficient evidence in the submission from the Southern NSW broadcasters and ACMA field survey reports to conclude that significant populations in areas such as west Hilltop, Helensburgh, Cordeaux Heights and Farmborough Heights, who rely on marginal reception of the Illawarra analog and digital television services will lose their television reception if there is a significant reduction in ERP to the north for the Illawarra digital television services. Compliance with technical specifications The effect of antenna height and lower frequency digital channels on coverage and overspill is not directly addressed in the submission, although it is implicitly considered in the submission statements that: the Southern NSW broadcasters are all broadcasting from Knights Hill in accordance with ABA/ACMA specified frequency, antenna height and antenna pattern; the ABA/ACMA determined these technical specifications for Knights Hill with the intention of affording good levels of coverage by the broadcasters within the licence area; the ABA/ACMA would have considered he level of overspill was a necessary consequence of delivering an appropriate level of coverage within the licence area; and any changes to the Knights Hill services will result in significant additional costs to the broadcasters and to viewers. The preliminary report concluded that the Illawarra commercial analog and digital television services are substantially operating as per their LAP and DCP technical specifications. The preliminary reported noted that the calculated ERP of the WIN and Southern Cross digital television services slightly exceeded the maximum ERP specified in the DCP. The submission states that the WIN and Southern Cross services now comply with the maximum ERP specified in the DCP. The preliminary report also Australian Communications and Media Authority 6

8 noted that the horizontal radiation pattern (HRP) of the transmission antennas exceeded the radiation mask specified in the DCP over the sectors 330ºT - 340ºT and 150ºT to 160ºT but that this was not an unusual discrepancy and the licences for the digital television services had been issued to reflect the actual antenna HRP. The technical specifications for the digital television services were planned in a draft combined national and commercial DCP released for comment by the ABA on 5 May 1999, with submissions closing on 31 May 1999, and confirmed in a final DCP released on 1 July The DCP decisions were detailed in an Explanatory Paper to be read in conjunction with the: Digital Terrestrial Television Broadcasting Planning Handbook 1999, which provides the technical guidelines for planning services; and the ABA s General Approach to Digital Planning 1999, which sets out the legislative framework and policy issues surrounding the digital channel planning process. The DCP was developed with the assistance of the Digital Television Channel Planning Consultative Group (DTCPCG). The DTCPCG adopted 10 broad planning parameters and assumptions including the assumption that the DCP is to be based on capacity required to provide HDTV to the edge of the licence area (assumed approx 19.3 Mbit/s capacity) and overspill at the boundary addressed. The DTCPCG created sub-groups to consider digital channel planning options for the metropolitan areas and the Sydney sub-group comprised representatives from the ABA, ABC, NTA (now Broadcast Australia), SBS, DCITA Communications Laboratory, Networks Seven, Nine and Ten, Prime Television, Ten Capital, WIN, NRN, NBN and News Ltd. The sub-group held meetings on 30 September 1998, 28 October 1998, 4 December 1998, and 21 January 1999 to discuss digital channel options for the Sydney, Newcastle and Illawarra high power sites. There were submissions to the draft DCP stating that the Knights Hill UHF digital service should be restricted [in ERP] in the north to avoid excessive overspill into the Sydney commercial service area. The submissions to the draft DCP were discussed in an ABA Board Paper of 17 June 1999 with the ABA Planning Branch advice that surveys assessing current analog overlap show field strength levels exceed the allowable Band V service boundary of 67 dbuv/m. However, this is a by product of the ERP required by analog services to adequately serve the Wollongong area, which will similarly apply to digital services. The ABA heeded this advice and decided not to take action on this aspect of the draft DCP. Allocations Branch is of the view that the current height, antenna pattern and frequencies of the transmitters at Knight Hill have been planned as necessary to achieve adequate levels of coverage within the licence area of the Southern NSW Broadcasters. The planning for the relevant LAP and DCP took place within the context of established ABA/ACMA planning processes. Australian Communications and Media Authority 7