Archived — Report on AM Broadcasting Possibilities in The Greater Toronto Area
Douglas R. Forde
April 17, 2001
Table of Contents
- Executive Summary
- Historical Perspective
- Rules and Agreements
- Overview of all AM Channels
- Review by Channel
- Appendix 1. Letter from Gordon Elder on sharing Toronto Island sites
- Appendix 2. Studies required to assess feasibility of second adjacent channel co-siting
1. Executive Summary
This report relates to AM broadcasting aspects of Industry Canada's response to CRTC Public Notice 2001-10, Report to the Governor in Council on measures to ensure that the residents of the Greater Toronto Area receive a range of radio services reflective of the diversity of their languages and cultures. It contains the author's analysis of the engineering report which the CRTC commissioned from Imagineering Limited on this topic, as well as the results of his own studies.
The Imagineering report reviews all current radio broadcasting bands and provides recommendations on each. The following table contains a summary of the possibilities in the AM band identified by Imagineering or the author:
|Channel||Potential Coverage (km in max. dir.)||Comments|
|790||70||11||Suitable site unlikely to be found. Could operate at lower parameters if colocated with existing station near market.|
|940||70||2||Requires exception to night-time protection rules. Siting would be difficult. Could operate at lower parameters if colocated with existing station near market. Mutually exclusive with 950.|
|950||80||30||Former Barrie station. Needs access to port lands site.|
|1100||50||0||Day only. Mutually exclusive with 1110.|
|1110||120||2||Can share Toronto Island site|
|1190||90||0||Day only. Mutually exclusive with 1200.|
|1200||80/120||10/35||From Oakville site/ from port lands site|
|1280||0Footnote *||0Footnote *|
|1470||Footnote **||25Footnote **||Formerly used by CHOW Welland and fully equipped site available for sale. Serves most of GTA daytime, but subject to interference at night. Moving closer to Toronto is possible if CHKT's Toronto Island site can be shared.|
|1480||40||3||Formerly used by CKAN Newmarket; site dismantled. Difficult to serve much of GTA at night. Mutually exclusive with 1470 and 1500.|
|1500||85||6||Siting difficult for night operation. Day can site anywhere and could have 60 km non-directional service. Mutually exclusive with 1480.|
|1580||70(ND)||4||Requires exception to night-time protection rules.|
|1610Footnote ***||70||12–25||LP station CHEV would be displaced. Markham application would serve only NE corner of GTA night|
|1650Footnote ***||70||12–25||May be incompatible with application on 1670.|
|1670Footnote ***||70||12–25||East York application could switch to 1650 or 1690 to ensure availability of third channel|
|1690Footnote ***||70||12–25||May be incompatible with application on 1670.|
Good coverage of the GTA, particularly downtown Toronto, requires a lakeshore or Toronto Island site for the high AM channels. Multilingual stations CHKT on 1430 kHz and CHIN on 1540 kHz currently use Toronto Island sites, which could potentially be shared with new stations on two other channels. (See Appendix 1, a letter from J. Gordon Elder, P. Eng., who designed and built these two stations.) In addition, the port lands and Leslie Street Spit area shown in Figure 2.3c of the Imagineering report would be a very good location for at least two other channels below 1600 kHz, as well as any or all of the five available channels in the expanded band.
I wish to acknowledge and thank Jean Alain of the Broadcast Applications Engineering Division for the excellent technical support, especially the provision of the maps included in the report.
Thanks are also due to Paul Vaccani and Kirit Mehta for their excellent constructive comments and ideas, and to both Kirit and Jean for ensuring that I had the necessary software and materials to carry out this project.
I also acknowledge with thanks the contribution of Gordon Elder, whose expert analysis of the possiblity of sharing the existing Toronto Island facilities which he designed and built, are shown in Appendix 1.
3. Historical Perspective
AM broadcasting has existed since the early 1900s, the first commercial station being CFCF Montreal on 600 kHz. The first international agreement was the 1937 North American Regional Broadcasting Agreement (NARBA), revised in 1950 when the top of the band was moved from 1550 to 1600 kHz. This agreement included, though not all at the same time, Canada, USA, Mexico, Bahamas, Dominican Republic and Cuba. It included basic protection criteria which are still mostly applicable today. It also included a division of channels, with some "clear" channels designated for national coverage, a good number of regional channels which generally were capable of serving large metropolitan areas and a few local channels intended for simple inexpensive operations to serve small cities and towns.
In 1982, with the signing of the ITU Region 2 Agreement (Rio 1982 Agreement), the channel designations in NARBA were replaced by class designations. The "clear" channels were replaced by class A which have substantial, but not national, service contours. The local channel stations became class C, mostly 1000 watts non-directional, and everything else became class B. Simultaneously with ratifying the Rio 1982 Agreement, Canada abrogated, i.e. officially withdrew from, NARBA The Region 2 agreement was complemented in 1984 by a bilateral agreement between Canada and the USA which elaborated the technical criteria somewhat and added a number of allotments which made use of the relaxed protection of the former clear channel stations. Many of these allotments were quickly taken up by existing stations to improve their coverage. For example, CFGO Ottawa improved day and night service moving from 1440 to 1200 kHz, and CFGM (now CFYI) Richmond Hill, which had fairly good day service and very limited night service on 1320 kHz, now serves the entire GTA, day and night, on 640 kHz. Figures 1 shows the present coverage of this station, which is typical of the low frequency, high power Toronto stations located south of Lake Ontario. Of these former clear channels, only 1200 kHz and possibly 1500 kHz still offer the possibility of new service both day and night in the GTA.
In 1988 another Region 2 agreement expanded the AM broadcasting band upwards from 1600 to 1700 kHz. This agreement divided the ten new channels equally among neighbouring countries in border areas, e.g. 1610, 1630, 1650, 1670 and 1690 kHz for Canada and 1620, 1640, 1660, 1680 and 1700 kHz for the USA. On its "priority channel", a country can put a 1 kW non-directional station anywhere within the area designated in the Agreement or can increase power up to 10 kW provided that interference would be no worse than could be caused by a 1 kW station at the border. This "expanded band" has hardly been used in Canada with only a few low power stations, mostly on 1610 kHz. It offers good possibilities for ethnic broadcasting in the GTA and includes two current applications.
A practice in the 1990s by AM stations with modest service who were also looking for the higher fidelity available in the FM band was what the CRTC referred to as AM-FM flips. This has also left a few AM channels which can provide a degree of service in the GTA. Most notable is the former CBC channel of 740 kHz, which has superb GTA coverage. This channel has been taken over by a new operator, who is leasing the CBC facilities and using them exactly as before. A bi-product of this is that the new operator, who already operated an ethnic station in the GTA has increased the ethnic programming on that station Three other interesting channels, which are studied in detail, are 950 kHz from Barrie, 1390 kHz from Ajax and 1470 kHz from Welland.
4. Rules and Agreements
Industry Canada's main regulatory document pertaining to AM broadcasting is Broadcast Procedures and Rules 2 (BPR2), supplemented by general provisions in BPR 1. However, most of the technical criteria to be met by AM applications are found in the 1984 bilateral agreement between Canada and the USA which is referenced in BPR 2.
With propagation being much more complex in the AM band than in the VHF and UHF bands used by FM and TV broadcasting, separation distance tables are impractical and protection from interference is obtained using protected contours and ratios. There are two propagation modes in AM broadcasting, groundwave, where the signal travels along the surface of the earth and attenuation varies with the type of terrain, and skywave, where the signal is reflected off the ionosphere. Groundwave propagation occurs day and night and varies with frequency as well as terrain. Skywave propagation occurs only at night because of the sun's affect on the ionosphere. Thus rules differ from day to night, although the same protection ratios apply. The protected contour day-time is generally 0.5 mV/m and is noise limited. The protected contour night-time is generally interference limited and is calculated for each station.
As mentioned in the Historical Perspective section, there are three classes of station:
- Class A, 50 kW maximum power, protected to 0.1 mV/m contour day and 0.5 mV/m skywave contour night.
There are very few class A stations and most use 50 kW with either a non-directional or simple directional antenna. Coverage generally exceeds 100 km day and can exceed 1000 km at night.
- Class B, 50 kW maximum power, protected to 0.5 mV/m contour day and 2.5 mV/m or existing interference level at night, whichever is greater.
There are many class B stations with powers ranging from 100 watts to 50 kW, some with very complex directional antennas. Some, mainly in the USA, operate only in the day because they cannot meet protection rules at night. Coverage can range from about 20 km to well over 100 km day, and from a few km to 50 km or more at night.
- Class C, 1 kW maximum power, protected to 0.5 mV/m contour day and 4 mV/m or existing interference level at night, whichever is greater.
There are many class C channels, most with 1 kW non-directional power on the former NARBA local channels. Coverage ranges from about 10 to 50 km day, and from about 2 to 15 km at night.
Protection ratios are:
- co-channel: 20 dB
- 1st adjacent: 0 dB
- 2nd adjacent: -20 dB
There is a 0 dB protection ratio for image interference (900 to 920 kHz apart), but exceptions are often made to this rule with little impact. It should be reviewed with modern receivers. There is also a prohibition of overlap of 25 mV/m contours for third adjacent channels.
As noted in the Historical Perspective section of this report, the "expanded band" 1610–1700 kHz is subject to a different agreement, which brings in the concept of "priority channel". The particulars of that concept are described in that section. Other than that difference, the rules above apply. Stations in this band are treated as class C, although they can raise power to 10 kW provided they would not cause more interference than a 1 kW non-directional station at the border.
4.1 Rules Needing Review
Imagineering notes three rules which should be reviewed:
- Night-time protection of Class A stations
Since no protection of skywave service has been required of adjacent channel stations, erosion of that service has resulted. This rule can be looked at from two aspects, both of which could be adopted:
- Class A stations should be protected only to their interference-free contour.
- Protection from adjacent channel interference should be added.
Even if the rule is not changed, it can be waived on a case-by-case basis where circumstances warrant.
- Image interference
Exceptions to the image rule rule have been made frequently, accompanied by a commitment to resolve interference complaints. To the best of my knowledge, such complaints are rare, if they occur at all. Receivers should be tested to see if this rule can be deleted.
- Third adjacent channel 25 mV/m overlap rule
Exceptions to this rule have been much less common, but again they have not created serious problems. Again receiver testing can provide an indication whether the rule should remain or be amended. This criterion may be frequency sensitive, a factor to consider in the testing.
I recommend that a B-TAC subcommittee look into these rules. Even if the rules are retained, exceptions should (continue to) be granted when circumstances warrant.
5. Overview of All FM Channels
|Channel kHz||Stations precluding use of channel|
|540||CBEF Windsor||530 CIAO Brampton|
|550||WGR Buffalo NY|
|560||CFOS Owen Sound|
|580||590 CJCL Toronto|
|600||590 CJCL Toronto|
|610||CKTB St Catharines|
|620||610 CKTB St Catharines|
|630||640 CFYI Richmond Hill|
|640||CFYI Richmond Hill|
|650||640 CFYI Richmond Hill|
|660||WFAN New York NY|
|670||680 CFTR Toronto|
|690||680 CFTR Toronto|
|700||710 CJRN Niagara Falls|
|710||CJRN Niagara Falls|
|720||710 CJRN Niagara Falls|
|730||740 CHWO Toronto|
|750||740 CHWO Toronto|
|760||WJR Detroit MI|
|770||WABC New York|
|790||can use 790 Brampton|
|800||CKLW Windsor||790 Brampton|
|810||820 CHAM Hamilton|
|830||820 CHAM Hamilton|
|840||WHAS Louisville KY|
|850||860 CJBC Toronto|
|870||860 CJBC Toronto|
|880||WCBS New York NY|
|890||900 CHML Hamilton|
|910||CKLY Lindsay||900 CHML Hamilton|
|930||WBEN Buffalo NY|
|950||can use Barrie allotment|
|970||WNED Buffalo NY|
|990||WDCZ Rochester NY|
|1000||1010 CFRB Toronto|
|1020||1010 CFRB Toronto|
|1030||WYSL Avon NY|
|1040||1050 CHUM Toronto|
|1060||1050 CHUM Toronto|
|1080||WUFO Amherst NY|
|1100||can use day-time|
|1110||can use with limited night operation|
|1120||WHTT Buffalo NY|
|1130||WBBM Chicago IL|
|1140||1150 CKOC Hamilton|
|1160||1150 CKOC Hamilton|
|1170||WWVA Wheeling WV|
|1190||can use 1190 Mississauga day-time|
|1200||can use Tillsonburg allotment||1190 Mississauga|
|1210||WPHT Philadelphia PA|
|1220||WKNR Cleveland OH|
|1230||WECK Cheektowaga NY|
|1240||1250 CJYE Oakville|
|1260||1250 CJYE Oakville|
|1270||WHLY Niagara Falls NY|
|1280||LP CFYZ Toronto Airport-see 1280 in Review by Channels|
|1300||WXRL Lancaster NY|
|1310||1320 CJMR Oakville|
|1330||1320 CJMR Oakville|
|1340||1350 CKDO Oshawa|
|1360||1350 CKDO Oshawa|
|1370||WXXI Rochester NY|
|1390||can use Ajax allotment|
|1400||WWNS Buffalo NY|
|1420||CKPT Peterborough||1430 CHKT Toronto|
|1440||WJJL Niagara Falls NY||1430 CHKT Toronto|
|1470||can use 1470 Welland allotment; CJOY limits day coverage in west||1470 night combined with 1480 or 1500 day|
|1480||can use 1480 Newmarket allotment|
|1490||WBTA Batavia NY|
|1500||can use day-time|
|1520||WWKB Buffalo NY|
|1530||1540 CHIN Toronto|
|1550||1540 CHIN Toronto|
|1560||WQEW New York NY|
|1570||WBUZ Fredonia NY|
|1580||can use day-time, night use questionable; may conflict with 1610|
|1590||WASB Brockport NY|
|1610||LP CHEV Toronto, Markham applicationFootnote *|
|1630||Footnote *see below|
|1650||can use if 1670 kHz application moves to 1690Footnote *|
|1670||application (should move to 1650 or 1690)Footnote *|
|1690||can use if 1670 kHz application moves to 1650Footnote *|
The shaded channels are available to serve all or part of the GTA. The type face used indicates roughly the value of the channel as follows:
|Day coverage||all GTA||all or most of GTA||majority of GTA|
|Night coverage||majority of GTA||city core||part or none|
6. Review by Channel
This channel was formerly used by CIAO Brampton and Imagineering notes the difficulties associated with operation at the old site, as well as finding an appropriate new site. They note that this channel has some potential as a very small one or 2-tower operation co-sited with an existing Toronto station close to the intended market. I concur that there are too many constraints, both day and night, to rebuild a 5 kW station. However, with the relatively low frequency and Eu, the possibility of serving part of the GTA at reasonable cost exists.
Imagineering notes that use of this new channel would require relaxation of day-time protection requirements to an adjacent channel allotment in Barrie and night-time protection requirements to CINW Montreal. My analysis of these possible rule exceptions is shown below. Imagineering also notes that day-time coverage would be limited by interference from WBEN Buffalo NY on 930 kHz. The corollary to this is that the new station would wipe out existing reception of WBEN in the GTA. Such reception is, of course, not protected, but loss of it presents a potential public relations problem. Add in the very limited night service, even if the rules are relaxed, and this is not a desirable channel, but I would not rule it out because of the high demand.
My analysis of night-time interference to CINW shows that the border points in southern ON — the 0.5 mV/m contour extends beyond the border — are subject to some co-channel and adjacent channel interference. Along the southern QC border, CINW's signal is strong enough that it is protected on a ratio basis. In eastern Canada, adjacent channel interference is severe from strong signals on 930 kHz and there would be no usable service. Also, the western limits of the skywave contour are subjected to both co-channel and adjacent channel (950 kHz) interference of significant magnitude. It would be reasonable to permit an applicant to establish an interference-free contour for CINW, skywave or groundwave, whichever extends further, and protect that. Concerning the adjacent channel allotment in Barrie, I would favour relaxing day-time protection criteria for these reasons:
- A station is more valuable than an allotment in terms of service to the public.
- The Barrie allotment was abandoned by CKBB because a good FM channel was available. This is not the case in Toronto.
An alternative to using 940 kHz is moving the 950 kHz Barrie allotment to Toronto. The 3-tower 2.5 kW night pattern formerly used at Barrie would need only a minor adjustment to protect CKNB Campbellton NB. The Eu drops from 22 to 18 with the move south, quite a usable value. This does not appear to be possible using existing towers The port lands and Leslie Street Spit area shown in Figure 2.3c of the Imagineering report would work with the Barrie night pattern rotated four degrees counterclockwise. A 1 kW day operation is also possible from this site, though it would conflict with the 960 kHz allotment at Cambridge. Alternately, a station could use 940 kHz day-time and 950 at night. If a 1200 kHz operation is also built at this site, the 950 kHz could probably be designed to share the same towers. (The reverse is not true because the constraints on 1200 kHz are more severe.)
The following map shows the predicted day and night coverage for these parameters.
Possible Coverage on 950 kHz = Couverture possible à 950 kHz
Day = Jour
Night = Nuit
Imagineering notes that this would be a day-time only operation, with interference-limited coverage because of class A station WTAM Cleveland OH. This channel is even less desirable than 940 kHz, except that it does not require rule-bending.
An alternative to 1100, this channel was formerly used at Sarnia ON and can be used day-time at any existing site with a day-time power up to 50 kW. Night use would be severely limited because of protection requirements to two US class A stations. Possibilities are a multi-tower operation with 1 kW or less and a directional antenna (DA) pattern aimed due north or low power in the order of 10 watts. I could not find an existing site which could accommodate the necessary DA. Figure 1110.1 shows possible day coverage using two towers from CKHT's Toronto Island site. Figure 1110.2 shows day urban coverage (25 mV/m) and coverage from a 20 watt night operation using the same towers.
This day-time only channel was formerly used in Mississauga and provided good day service. It can be co-sited with any station north of the lake.
An alternative to 1190 is 1200 kHz. This channel was intended for day-time station CKOT Tillsonburg ON, but the latter has not filed an application despite the availability of a reasonable night-time operation and a day-time operation comparable to or better than its current 1510 kHz. This channel would not be quite as good as 1190 day-time, but could serve part of the GTA at night.
The ideal location to serve Toronto with 1200 kHz would be Toronto Island, but the antenna arrays there are not suitably oriented to provide necessary protections with reasonable power. The best antenna array from that aspect is that of CJMR/CJYE Oakville. I have designed a 700 watt night pattern whose coverage is shown in Figure 1200.1. I could only meet day-time protections from that site with a 4 kW operation, coverage also shown in Figure 1200.1. If an applicant wants more extensive day coverage, 1190 kHz is available.
Day – outer black contour; night – inner red contour
Since the 950 kHz night pattern is similar to the pattern required for 1200 kHz at night, I tried using the towers which produced the coverage shown in 950.1 from a site in the port lands identified by Imagineering as a good location, if available. This was unsuccessful, so I tried moving the array from the Tillsonburg 1200 kHz allotment to that site. With an adjustment of phases, this worked and the possible coverage from this 10 kW operation is shown below. A day operation at 25 kW with the same antenna pattern is possible.
Day – outer black contour; night – innter red contour
This channel was formerly used in Hamilton and is now used by low power information station CFYZ at Pearson Airport. Imagineering concludes that this channel cannot be used near the lakeshore because of co-channel protection requirements to WHTK Rochester NY. This means that only communities away from the shore could be served and I doubt whether coverage significantly superior to what CFYZ has could be obtained. In summary, this is not a viable option for an ethnic broadcasting service.
This Ajax allotment is based on the operation of former station CHOO. Since the main day-time constraint is to the southwest (CKPC Brantford), a suitable site southwest of Toronto was sought, with the site of CJMR/CJYE Oakville seeming appropriate. A 3 kW night pattern was designed using four of the towers in the 7-tower array. Unfortunately, this site is too close to the protected contour of adjacent channel station CKPC Brantford to provide day service. A 3 kW day operation from CHKT's site on Toronto Island is possible using 4 existing towers and two additional towers located between them. Unfortunately, this array is not as well suited to meeting night protections and I could only obtain a 1 kW operation using a different 6-tower combination. However, most applicants would still consider it a more desirable coverage than the 3 kW possibility from the western site. The three contours are shown in Figure 1390.1.
Recently used by CHOW Welland, Imagineering states that the site and antenna array are intact and for sale. They would provide an applicant with deep pockets instant day-time coverage of much of the GTA while he looks into moving the operation closer to Toronto for full-time coverage. Imagineering notes the conflict with the 1480 kHz Newmarket allotment if 1470 is moved north. I note, however, that the previous user of the Newmarket allotment was never satisfied with his service, particularly the very limited night service, and eventually shut down. Thus, if faced with a choice of keeping 1480 or getting a good GTA service on 1470, my choice would be the latter. Imagineering did not think that co-siting on Toronto Island would be practical, but I consulted Gordon Elder, P. Eng., who designed and built the two existing AM operations on the island, and his response is given in Appendix 1. Mr. Elder comments that 1480 kHz could provide better day service to the western part of the GTA. A possible option, maybe too costly, is to use 1480 or 1500 day-time and 1470 at night. A precedent for such a two channel operation existed in Leamington where a station operated on 710 kHz day-time as CHIR and switched to 730 kHz at night as CHYR. This twin operation carried on from the 1970s till recently when the station switched to FM. Possible night parameters, using CHKT's existing antenna array at 3 kW follow. Figure 1470.1 shows predicted coverage with these parameters. Figure 1470.2 shows the overlap between CJOY Guelph on 1460 kHz and a day operation using the night parameters at 10 kW, confirming Mr. Elder's comments.
Imagineering points out the limitations of this channel and do not see it as a practical alternative for serving the GTA, especially since it would preclude use of 1470 kHz. My initial reaction was to concur, but due to the comments in the appended letter from Gordon Elder about 1480 offering better day-time service, I decided to look more closely and my analysis follows.
The best location for 1480 kHz to serve the GTA from is Toronto Island. With the limited design software available at Industry Canada, I came close to meeting protection requirements with a 1 kW night pattern using CHKT's towers. With an Eu of 30 mV/m, this will not provide much service and I do not consider this to be a practical option.
Imagineering suggests this as a day only channel. This could work with 1470 kHz, if cosited or if we waive the third adjacent channel protection rule. It would probably not work with 1480 kHz unless day coverage were limited to what is available on 1480. An alternate possibility is to use 1470 kHz at night and 1500 in the day-time.
Imagineering notes that use of this new channel would require relaxation of night-time protection requirements to CBJ Chicoutimi QC. My assessment of that proposal is shown below. Siting needs to be chosen with care to avoid image problems with CFTR on 680 kHz and third adjacent channel problems with 1610 kHz. If it comes down to a choice between 1580 or 1610, the latter offers much better night service and is preferable.
1610, 1630, 1650, 1670 and 1690 kHz
It is theoretically possible to use all five channels if they are co-sited and use nearly identical parameters. Currently, there is an application on 1610 kHz at Markham ON with 10 kW day and 5 kW night, 2-tower directional antenna, which appears to meet the bilateral agreement criteria and would provide fairly good GTA coverage day-time, but only serve the north-east part of the GTA at night. There is also an application in East York on 1670 kHz with 10 kW day and 1 kW night, non-directional, which may meet the bilateral agreement criteria, and would provide adequate GTA coverage day-time and downtown service at night. If suitable filtering and combining equipment could be found, the East York site could be used for a 5-station operation. While it would be costly to combine the five signals and may require some compromise in bandwidth, the cost savings of a single site operation would be significant. This option definitely merits further study. See appendix 2.
If it is not practical to combine signals separated by 20 kHz, the 1670 kHz applicant should be asked, perhaps required, to apply for 1650 or 1690 kHz instead. This would at least allow three expanded band stations in the GTA.
Optimum service to the GTA on these channels could only be provided from Toronto Island or the port lands using a simple directional pattern and 10 kW day and night. If these areas are not available, the East York proposal mentioned above is a fairly good second choice.
Appendix 1 – Letter from Gordon Elder on sharing Toronto Island sites
Elder Engineering Inc.
P.O. Box 10, King City, Ontario
Broadcast and Communications Consultants
Area Code: 905
February 26, 2001
Mr. Douglas Forde
AM Broadcast Engineering
300 Slater Street
Ottawa, Ontario K1A 0C8
Subject: Sharing an AM Transmitting Site, on Toronto Island
This follows CRTC P.N. 2001–10 of January 31, 2001, concerning engineering requirements to increase the diversity of ethnic programming in the GTA and specifically AM radio, which is discussed in paragraph 56.
As you know, I became very familiar with the island sites in 1960, as CKEY's consultant for their facilities at Gibraltar Point. Later, we designed and commissioned CHWO and CJMR's jointly owned seven tower shared array, on the mainland. It operates on 1250 and 320 kHz in Oakville.
CHIN's 1540 kHz array is immediately SSW of CHKT's on 1430 kHz. All eleven ATU's have filters to avoid reradiating and distorting the adjacent station's pattern.
The following are only preliminary comments. A detailed design, SC-5 analysis at the school, capital cost estimates, including for freight and installation, negotiations with the licensee and the City of Toronto, would be essential. The three frequencies under consideration and their approximate NL's are:
|kHz||Approximate NL (mV/m)|
The night pattern on 1500 kHz would require suppression to very low radiation levels, over the 225° arc from east to northwest, in order to protect WTOP and KSTP's skywave service. A special array design would be necessary. In our opinion, sharing either CHIN's or CHKT's site and all or part of their array, would not be feasible, due to the severe constraints and complications. Neither would a suitable separate Island or adjacent lakefront site be available for a 1500 kHz station, due to Toronto's current land use leasing restrictions and prudent avoidance policies.
1470 kHz has a lower night limit, but its daytime service to Mississauga would be poorer then 1480 kHz's, in order to protect CJOY, Guelph. If either of these frequencies was selected and the assignment co-sited with CHIN, the field intensifies at CHKT's array would be much stronger than would occur at CHIN's, if it was co-sited with CHKT. Therefore, less tower reradiation and filter suppression would be required, if the new 1470 or 1480 kHz station shared CHKT's array.
This concept is technically feasible, but perhaps not economically feasible. Complex design details are involved, which may reduce the system's reliability. For example, the small difference in frequency of approximately only 3% or 40–50 kHz, would require excellent filter-combiner design techniques. Additional coaxial cables, larger ATU huts and additiooal floor space for the new transmitter and phasor would be required. For these reasons, CHKT's licensee – Fairchild Radio, may be reluctant to share its transmitting site and array, especially with a potential competitor.
The site sharing difficulties would depend upon the applicant's desired service area, power and antenna pattern requirements, of course.
At your discretion, part or all of this letter may be submitted to IC and/or CRTC. if desired or required.
Yours very truly,
Appendix 2 – Studies Required To Assess Feasibility Of Second Adjacent Channel Co-siting
1. Filtering and combining equipment
Vendors of filtering and combining equipment for AM broadcasting should be surveyed to determine whether it is technically feasible to design and build equipment to combine up to five signals 20 kHz apart in the 1600–1700 kHz band. A first approximation of cost to build and install should also be obtained.
2. Receiver testing
A sample of current receivers should be tested to determine whether the existence of multiple signals would create destructive beats across the AM band. The tests should use signal levels as high as practical to simulate conditions near the broadcasting site. DGSE's laboratory is capable of undertaking such tests.
- Date modified: