sowny.net | The Southern Ontario/WNY Radio-TV Forum


You are not logged in. Would you like to login or register?

November 17, 2021 4:52 pm  #1


How Many FM Stations Were On The CN Tower When It Opened?

It's easy to think nearly every Toronto FM station jumped onto what was then the world's largest free standing structure when it was finished. But according to this ad, which appears to be from 1976, there were only five of them: CBL-FM, CHFI, CKFM, CHIN-FM, and CHUM-FM. I've never heard of "The Toronto Group of FM Broadcasters" before. Was this just a CN Tower thing? Does it still exist? 

https://i.ibb.co/xmZGzg8/CN-Tower-FM-1976.jpg


I don't recall the campaign below, either. But I assume CJRT raised the money it needed to make the leap in 1980. 

https://i.ibb.co/2t3NYJm/CJRT-CN-Tower-1980.jpg

 

November 17, 2021 6:11 pm  #2


Re: How Many FM Stations Were On The CN Tower When It Opened?

Yes I believe the big-wig stations such as those you have listed, had to collaborate and setup a plan for their single antenna system and developed "Master FM".  Q107 came on in 78 I believe, CFNY in 83? and 97.3 in the late 80s.  


https://www.broadcasting-history.ca/industry-government/cn-tower-story

Last edited by markow202 (November 17, 2021 6:52 pm)

 

November 17, 2021 8:07 pm  #3


Re: How Many FM Stations Were On The CN Tower When It Opened?

It's always been fascinating to me, in retrospect, to see how underbuilt the CN Tower was when it was planned and built. The original plan was to put all of the FM facilities (except the CBC's 94.1) in a single room that takes up about half of one of the "pod" levels. And indeed, from that day to this, those original FMs all sit cheek-by-jowl next to the combiner modules out in the open - CHFI, CKFM, CHIN-FM and CHUM-FM. 

The combiner had some expansion capacity, but not a lot, which is how CJRT, CILQ, CFNY and CJEZ were able to join into the master antenna. There wasn't floor space for more transmitters, though, so they ended up in new rooms down the hall. 

But the gobsmacking part, in retrospect, is that they built it with the capacity to handle eight FMs. The combiner and master antenna expertise certainly existed to build bigger systems to handle more stations and more power. The 1967-vintage Alford master antenna at the Empire State Building was designed to handle more than a dozen signals and eventually wound up with 13 of them. (A modern replacement can now handle 19 FMs!)

Building for more eventual capacity would have cost more money, of course, and it's understandable that the private owners of the four original commercial FMs wouldn't have wanted to lay out cash in 1977 for improvements that would only benefit eventual competitors. But the CBC might have been expected to want to plan ahead - and indeed, they paid the price later on when there wasn't room at the inn for their 99.1 to use the CN Tower when it hit the air two decades later. (I don't know as much about what happened with CJBC-FM - it apparently signed on from CN using an auxiliary port of the combiner but then moved to FCP when CBLA signed on there. 

In retrospect - and hindsight is 20/20, of course - it would probably have made more sense to put the transmitters and especially the combiner in a ground-level space, and then you'd only have needed a fat transmission line (8 or 10 inches across) going up the core of the tower to the antenna. It would have made expansion or replacement much easier. 

But I wonder, too, if there's some space that's freed up now at CN with the move to DTV. New TV transmitters are MUCH smaller than their analog predecessors. CFTO needed a good-sized room all to itself for an analog channel 9 transmitter in the 1970s. Its current channel 8 rig could probably fit in a medium-sized closet. Having seen how much space the analog 5 and 25 rigs took up in the CBC's room, I'm sure there's more space available there, too. The combiner is probably the biggest choke point for FM expansion now, as well as the power-handling capacity of the master antenna. (And replacing an antenna under the shroud there is another challenge unique to CN.) 

 

November 18, 2021 12:02 pm  #4


Re: How Many FM Stations Were On The CN Tower When It Opened?

fybush wrote:

It's always been fascinating to me, in retrospect, to see how underbuilt the CN Tower was when it was planned and built. The original plan was to put all of the FM facilities (except the CBC's 94.1) in a single room that takes up about half of one of the "pod" levels. And indeed, from that day to this, those original FMs all sit cheek-by-jowl next to the combiner modules out in the open - CHFI, CKFM, CHIN-FM and CHUM-FM. 

The combiner had some expansion capacity, but not a lot, which is how CJRT, CILQ, CFNY and CJEZ were able to join into the master antenna. There wasn't floor space for more transmitters, though, so they ended up in new rooms down the hall. 

But the gobsmacking part, in retrospect, is that they built it with the capacity to handle eight FMs. The combiner and master antenna expertise certainly existed to build bigger systems to handle more stations and more power. The 1967-vintage Alford master antenna at the Empire State Building was designed to handle more than a dozen signals and eventually wound up with 13 of them. (A modern replacement can now handle 19 FMs!)

Building for more eventual capacity would have cost more money, of course, and it's understandable that the private owners of the four original commercial FMs wouldn't have wanted to lay out cash in 1977 for improvements that would only benefit eventual competitors. But the CBC might have been expected to want to plan ahead - and indeed, they paid the price later on when there wasn't room at the inn for their 99.1 to use the CN Tower when it hit the air two decades later. (I don't know as much about what happened with CJBC-FM - it apparently signed on from CN using an auxiliary port of the combiner but then moved to FCP when CBLA signed on there. 

In retrospect - and hindsight is 20/20, of course - it would probably have made more sense to put the transmitters and especially the combiner in a ground-level space, and then you'd only have needed a fat transmission line (8 or 10 inches across) going up the core of the tower to the antenna. It would have made expansion or replacement much easier. 

But I wonder, too, if there's some space that's freed up now at CN with the move to DTV. New TV transmitters are MUCH smaller than their analog predecessors. CFTO needed a good-sized room all to itself for an analog channel 9 transmitter in the 1970s. Its current channel 8 rig could probably fit in a medium-sized closet. Having seen how much space the analog 5 and 25 rigs took up in the CBC's room, I'm sure there's more space available there, too. The combiner is probably the biggest choke point for FM expansion now, as well as the power-handling capacity of the master antenna. (And replacing an antenna under the shroud there is another challenge unique to CN.) 

Great info fybush!  I beleive it was you who did the 2015 article/visit up there.  Interesting and high tech rooms and txs.  In another post about HD radio in toronto I beleive someone wrote about putting a new master FM antenna in the old CBC analog section just above the current master FM unit and slightly lower power due to increased height.  However, given the age already of the current antenna (if that really matters as its metal) its working perfectly.
 

 

November 18, 2021 12:04 pm  #5


Re: How Many FM Stations Were On The CN Tower When It Opened?

 

November 18, 2021 12:20 pm  #6


Re: How Many FM Stations Were On The CN Tower When It Opened?

What's the state of the HAM repeater there? An internet search yields a lot of conflict and drama.

 

November 20, 2021 4:10 pm  #7


Re: How Many FM Stations Were On The CN Tower When It Opened?

fybush wrote:

It's always been fascinating to me, in retrospect, to see how underbuilt the CN Tower was when it was planned and built. The original plan was to put all of the FM facilities (except the CBC's 94.1) in a single room that takes up about half of one of the "pod" levels. And indeed, from that day to this, those original FMs all sit cheek-by-jowl next to the combiner modules out in the open - CHFI, CKFM, CHIN-FM and CHUM-FM. 

The combiner had some expansion capacity, but not a lot, which is how CJRT, CILQ, CFNY and CJEZ were able to join into the master antenna. There wasn't floor space for more transmitters, though, so they ended up in new rooms down the hall. 

But the gobsmacking part, in retrospect, is that they built it with the capacity to handle eight FMs. The combiner and master antenna expertise certainly existed to build bigger systems to handle more stations and more power. The 1967-vintage Alford master antenna at the Empire State Building was designed to handle more than a dozen signals and eventually wound up with 13 of them. (A modern replacement can now handle 19 FMs!)

Building for more eventual capacity would have cost more money, of course, and it's understandable that the private owners of the four original commercial FMs wouldn't have wanted to lay out cash in 1977 for improvements that would only benefit eventual competitors. But the CBC might have been expected to want to plan ahead - and indeed, they paid the price later on when there wasn't room at the inn for their 99.1 to use the CN Tower when it hit the air two decades later. (I don't know as much about what happened with CJBC-FM - it apparently signed on from CN using an auxiliary port of the combiner but then moved to FCP when CBLA signed on there. 

In retrospect - and hindsight is 20/20, of course - it would probably have made more sense to put the transmitters and especially the combiner in a ground-level space, and then you'd only have needed a fat transmission line (8 or 10 inches across) going up the core of the tower to the antenna. It would have made expansion or replacement much easier. 
 

The apparent lack of foresight has to be viewed in the context of the FM allocation plan in effect at the time.  The CN Tower signed on in 1976. The operative FM agreement between Canada and US the dated back to 1947, and was based on omnidirectional antennas with spacings based on tables: class-to-class and frequency spacing (adjacency).  The original allocation plan did allow for limited short-spacing of certain assignments in the border zone.
I have some of the original EMI master antenna documentation, and it lists 12 frequencies: 88.1, 89.5, 90.3, 91.1, 94.1, 97.3, 98.1, 99.1, 100.7, 104.5 and 107.1.  It was possible to add CFNY (102.1) because it was assigned to nearby Brampton, and could be relocated without violating the spacing requirements.
It wasn't until 1991 that Canada and the United States ratified a new FM agreement which allowed for significant short spacing and the use of highly directional antennas to achieve the required protections:

https://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/AGREEFM.PDF/$FILE/AGREEFM.PDF

Page 29 lists the Toronto assignments, and they are identical to the EMI frequency list with the exception of 99.1, which according to Table A limitation 6 was limited to 50 kW at 150 metres in the direction of the protected station. That is why CBLA-FM is on First Canadian place, operating at 98 kW directional with an EHAAT of 303.7. metres.

So to summarize, all Toronto frequencies which could operate with an omnidirectional antenna were taken into consideration in the original design.  CIUT operates on 89.5 from FCP because it costs less, not because it couldn't operate from the CN Tower, although the ERP would be significantly reduced because of the much higher EHAAT.

With the exception of CIUT-FM, all FM stations on First Canadian Place are operating with custom FM antennas with directional patterns which take into account the protection requirements of their particular frequency.  Needless to say, the patterns are all dramatically different with one exception.  CJBC-FM shares the CBLA-FM antenna as an economic measure, not because it needs the same directional pattern. Achieving the requisite directional patterns using panels on a pentagonal wide-face structure which supports the CN Tower antennas would be a tough nut to crack.Not impossible, but quite complex. The First Canadian Place towers are  only1.44 metres in face width.

While it is possible to use the same set of panels to create different directional patterns, that technique usually requires the use of a combiner for each face of the antenna so that the specific phase and amplitude component for each face of the antenna can be achieved. It has been done, but very rarely.

With regard to locating the transmitters in the basement of the CN Tower instead of the pod, again we need to think back to the transmitter technology available in 1976.  There were no solid state FM transmitters at the time, and most single-tube FM transmitters maxed out at 20 to 25 kW.  The Master FM antenna has five bays, circularly polarized, thereby achieving an average omnidirectional power gain of 2.29 to 2.93, depending on frequency.  As a full Class C1 requires 40 kW ERP, the required transmitter power delivered to the main antenna line for the Class C stations on the CN Tower ranges from 12.99 to 16.46 kw.  When you factor in the combiner loss on top of this, you can see that many of the transmitters would have been running close to their rated 20 kW output. Incidentally, many of the broadcasters utilized the Collins 831G (succeeded by the Continental 816R)
The EMI antenna was in fact manufactured under license from Alford, and had an input power rating of 150 kW per bay.

So the bottom line is that the Master FM antenna design was as good as it could be at the time.


 

 

November 20, 2021 5:32 pm  #8


Re: How Many FM Stations Were On The CN Tower When It Opened?

Thank you fybush and Skywave! I really appreciate your knowledge.

I've always believed Toronto faired very poorly in the 1947 agreement. Look at the number of allocations to Buffalo compared with Toronto. Montreal also faired very well. Why a C1 was allocated to Brampton baffles me. Same with the Guelph allocation that ultimately became CIDC in Orangeville. In the 80s Toronto did "steal" 96.3 -- originally allocated to Hamilton.

By most valid measures, Toronto's population is now greater than Chicago. That makes us the fourth largest city in North America. I wouldn't be surprised if on a per capita basis, Toronto has fewer FM allocations from that original agreement than any other city on the continent.

Skywave, if there were capacity and an openness to modernize the combiner/master antenna on the CN Tower, could CBLA and CJBC be relocated there - albeit at reduced power for both stations? I understand that CBLA has to protect to the south-east but could that not be managed with reduced power as is the case with CHBM?

Last edited by Tim Brown 2016 (November 20, 2021 5:34 pm)

 

November 20, 2021 7:19 pm  #9


Re: How Many FM Stations Were On The CN Tower When It Opened?

At the CN Tower's EHAAT of 420.5 metres, the power of CBLA-FM would have to be reduced to Class B equivalent (50 kW at !50 metres) which equals 4.5 kW. That would not provide the regional coverage that CBC needs. CJBC-FM is Class B, and operates at 10 kW maximum ERP at an EHAAT of 303.7 from FCP. It's maximum ERP from the CN Tower would also be 4.5 kW. For CJBC operating omnidirectional, there would be a coverage gain towards the southeast relative to its existing directional pattern.
CHIN and CHBM both started out as Class B equivalents, and at the time the ERP was calculated to be 4.0 kw (not 4.5).  Each of them applied for and received limited C1 status after the 1991 treaty came into effect.  CHIN increased power to 8.5 kW in 1992 and CHBM to 28.9 in 1994.
 

 

November 21, 2021 12:04 am  #10


Re: How Many FM Stations Were On The CN Tower When It Opened?

Great info!! How come CHBM isn’t 40k watts like most of the others and CHIN the lowest wattage? Do they just care for decent coverage in GTA only? Although I must say, despite the lower power of CHBM 97.3 it still has equal coverage of let’s say CHUM I didn’t see much difference when travelling to their fringe signal areas.  CHFI surprisingly the worst for me signal wise yet they are the strongest!

 

November 21, 2021 12:02 pm  #11


Re: How Many FM Stations Were On The CN Tower When It Opened?

Skywave wrote:

At the CN Tower's EHAAT of 420.5 metres, the power of CBLA-FM would have to be reduced to Class B equivalent (50 kW at !50 metres) which equals 4.5 kW. That would not provide the regional coverage that CBC needs. CJBC-FM is Class B, and operates at 10 kW maximum ERP at an EHAAT of 303.7 from FCP. It's maximum ERP from the CN Tower would also be 4.5 kW. For CJBC operating omnidirectional, there would be a coverage gain towards the southeast relative to its existing directional pattern.
CHIN and CHBM both started out as Class B equivalents, and at the time the ERP was calculated to be 4.0 kw (not 4.5).  Each of them applied for and received limited C1 status after the 1991 treaty came into effect.  CHIN increased power to 8.5 kW in 1992 and CHBM to 28.9 in 1994.
 

Just curious how the allocation for 99.1 got downgraded. When I worked at CKO, we were licensed as a C-1 and eventually ran 100,000 watts from FCP. Did the 1994 amendments affect that allocation? If memory serves, the frequency was vacant in 1994 and therefore didn't have a commercial interest advocating for it.

If relocated to the CN Tower's omnidirectional antenna, would CBLA really need to operate as a B class equivalent - even for that fairly slight protection to the south-east?

I'm certainly not doubting your authority on this. I'm just wondering what was behind the change.

 

November 21, 2021 2:47 pm  #12


Re: How Many FM Stations Were On The CN Tower When It Opened?

The very, very old class B allocation on 98.9 in Rochester (long WHFM, now WBZA) is what mandates the protection from 99.1 Toronto. 

Until the late 1980s, Rochester didn't operate with full class B facilities - it was 50 kW, but on the relatively short tower of its then-sister station, WHAM 1180, on low ground southwest of Rochester. I suspect (but don't know for sure) that's why CKO was able to use 100 kW from Toronto at the time. 

 

November 21, 2021 10:34 pm  #13


Re: How Many FM Stations Were On The CN Tower When It Opened?

There was a call for applications in 1991 for the 99.1 frequency after CKO folded.  There were 3 applicants at the time, who were heard at a hearing in 1992.  All 3 applications were denied.  Several years later CBC applied to flip CBLA from 740 khz to 99.1 and it was approved.   Here's an extract from the decision denying the (commercial) applications for 99.1.Rawlco Communications Ltd. (Rawlco), which has been licensed to provide a new country music FM service in Toronto on the frequency 92.5 MHz (Decision CRTC 90-693), was the first to file its current application to switch to 99.1 MHz. Following receipt of Rawlco's application, the Commission issued a call for applications from other FM broadcasters in the Toronto area wishing to make use of that frequency (Public Notice CRTC 1991-126). The above-noted applications by Redmond Communications Ltd. (Redmond) and Mr. Martin Rosenthal were filed in response to the call. Redmond is the licensee of CJEZ-FM Toronto, which operates in a Group I Easy Listening format. Mr. Rosenthal is the licensee of the programming undertaking consisting of CFMX-FM Cobourg and its rebroadcasting transmitter CFMX-FM-1 Mississauga, and offers a service consisting predominantly of classical music. Mr. Rosenthal proposed to change the frequency and location of the Mississauga transmitter.The Commission stated in its 1991 call that, in considering any applications for use of 99.1 MHZ in the Toronto area, it would be concerned with what would constitute the most appropriate use of this frequency. Although the call was limited to existing broadcasters seeking to upgrade their signals, the Commission emphasized that its decision to proceed in this manner should not be construed as any predetermination on its part that such use would represent the most appropriate use for the frequency. The Commission also reaffirmed the fundamental objective of the FM policy, that being to ensure that "...the overall services provided in any given market are as varied and comprehensive as possible".