Cbw

[cyberdad]

I've been wondering.....

Do any of you guys know the story behind CBW powering down from 50KW to 46KW at night (both non-directional)? On the surface, it seems kind of dumb. So I'm wondering....is dropping to 92% of day power due to some sort of international mandate (or for that matter a domestic one)? Is the CBC just trying to save a few bucks on the electric (or should I say "hydro") bill?
CBC trying to "go green"? Some other reason?

At 46KW, CBW's night signal is still a monster. Groundwave and skywave. So I'd have to say they're not losing much.

So does anyone here know what the deal is?

 

[MarioMania]

Is it still concered a Clear Channel Still?

 

[cyberdad]

To the best of my knowledge....and at least by today's classifications....CBW is effectively the dominant station on a Canadian Clear Channel. I'm not sure if 990 is/was a Canadian clear or a Canadian-Mexican clear. Perhaps someone more knowledgeable than me can clarify and/or correct.

What I do know is that CBW does get nighttime protection. Here in the Chicago area, not only is CBW a frequent nighttime pest for local WMVP (1000) in the far western suburbs, but it's almost always completely alone on the channel with a good signal. It's typically a much better signal here than WSB, which is equally distant but from the opposite direction.

 

[radioman148]

I can confirm Cyberdad's observation. Here at my location in the near north Chicago burbs, CBW is strong most nights.

 

[davideduardo]

To the best of my knowledge....and at least by today's classifications....CBW is effectively the dominant station on a Canadian Clear Channel. I'm not sure if 990 is/was a Canadian clear or a Canadian-Mexican clear. Perhaps someone more knowledgeable than me can clarify and/or correct.

Under the old designation, 990 was a B clear channel... more than one primary station. In this case, Montreal and CBW. And it is shared with Mexico... XET in Monterrey.

The slight night power reduction may be to protect one or another of the other stations.

Not much different from 690 with Montreal and Vancouver, as well as Tijuana and Mexico City (although the Mexican stations are directional) .

 

[Schroedingers Cat]

My guess is that they either went to a higher tower or changed location, and to afford the same protection, they reduced power. They could have used a Series Limiting Resistor, and relicensed with the actual power without the resistor wasting power. CBM 940 either went to a diplexed array or moved slighly at one point, and went to a directional antenna with the second tower with a 0.12 field ratio, which I suspect was to duplicate the groundwave or protect US stations to the same level as before. If you don't know all the treaty loopholes, sometimes stations are protected needlessly also, so it's hard to say why CBW went to 46000 watts without asking someone, or having access to old application records in Canada. I don't know if the Canadian Communication Foundation site with a lot of history from Bill Dulmage has the reason or not.

Just looked. They moved the transmitter in 1993. Here's the link.

http://www.broadcasting-history.ca/...ories/radio/histories.php?id=202&historyID=70

 

[Icangelp]

I guess this is one of the AM operations that will remain on the Medium Waves. I'm sure it serves a geographically large, sparsely populated area that looks to CBW for news and entertainment.

Though a person does have to wonder how long the Canadian government will remain in the broadcast business.

 

[cyberdad]

Thanks gentlemen, for shedding some light on this. The link posted by Schroedingers documents the relocation of the transmitter closer to the city in 1993, but gives no specific technical reason for the coinciding drop in night power. However, the comments above would certainly explain it. I also knew that CBW was a class "B" under the old designations, but I didn't know offhand what other station(s), if any, they might be obligated to protect. If I wasn't so lazy, I might have gone to David's excellent website, and been able to figure it out!

Finally, it's true that CBW, and for that matter, sister CKSB, puts a big signal into a lot of sparsely populated real estate, so it would absolutely make good economic sense for the CBC/SRC to keep these two going on the AM band for the forseeable future.

 

[Fingerboard Corners]

Thanks gentlemen, for shedding some light on this. The link posted by Schroedingers documents the relocation of the transmitter closer to the city in 1993, but gives no specific technical reason for the coinciding drop in night power. However, the comments above would certainly explain it. I also knew that CBW was a class "B" under the old designations, but I didn't know offhand what other station(s), if any, they might be obligated to protect. If I wasn't so lazy, I might have gone to David's excellent website, and been able to figure it out!

Finally, it's true that CBW, and for that matter, sister CKSB, puts a big signal into a lot of sparsely populated real estate, so it would absolutely make good economic sense for the CBC/SRC to keep these two going on the AM band for the forseeable future.

I'm not sure what direction they moved CBW, as haven't looked at the map. But say they moved East just a little bit, or South. They would potentially interfere more with these (heritage) call letters on 990, KNIN, WIBG, WNOX, and other stations on 990. They would have to decrease toward those based on a closer distance. If they went to a higher tower, the efficiency would be higher, and even at the same distance, it would increase interference without decreasing the power. KFI ran into problems just decreasing antenna height, since a lower electrical height would interfere with cochannel and first adjacent channels at a high elevation angles. They had to design a complex sectionalized tower to duplicate the tower and its vertical radiation characteristic of the one that got hit with a plane and then the replacement collapsed. So a combination of FAA and FCC regulations complicated an involuntary lowering of antenna height. Otherwise, they would have been forced to lower power also.

 

[mimo]

Unfortunately CKSB is dark. At least on AM. They moved FM only and set up a bunch of low powered repeaters around the province to provide the coverage that AM 1050 had. As for 990, there is also a CBC station in Newfoundland on 990. Montreal's 990 allocation is moving to 980, when Evanov launches later this year....that's because there is less to protect than their is at 990. The pattern they will have will send a lot of signal straight west, east and north...and none towards the nearest Canadian 980 in London or to the U.S. There was a 980 in Peterborough that had to be protected and that was why they moved to 990 in the first place, plus a low powered SCR repeater 100 km's north of Ottawa. Peterborouh's 980 went FM a few years ago.

 

[cyberdad]

When did CKSB go dark? I just heard them a month or two ago. Or at least I thought I did....light classical instrumental music on 1050, so I assumed it was them.

I thought CKSB would be around forever....given the number of widely scattered Francophone communities around southern Manitoba. My (obviously incorrect) assumption was that it would be more efficient to cover them with one big signal than a bunch of little ones.

 

[mimo]

It was very recent. They applied to convert the station to fm and the 90 day simulcast period just ended a month or so ago..you must have caught them just before they went dark. I thought they'd be around forever too. At least there's still CJBC 860. Or the Saskatchewan affiliate of SRC which is also on 860

 

[Gregg.]

For the record, an old 1977 Broadcasting Yearbook I have designates 990 as a Canadian Clear Channel frequency. XET Monterrey may run at 50,000 watts but has no similar protection. CBW was a Class I-A, one of 37 on the AM dial in North America.

As such, CBW originally had the maximum protection of Class I-A status, meaning all other stations on 990 had to protect it for many hundreds of miles around their city of license. The only other Canadian station on 990 was 10,000 watt CBY in remote Corner Brook Nfld. In the U.S., only six stations operated at night on 990: WIBG Philadelphia, KTKT Tuscon, WHOO Orlando and low power stations in New Mexico, Texas and Puerto Rico.

But now the pattern you have is grandfathered in. For instance, WBZ Boston and WWL New Orleans were the only I-A stations to operate with directional antennas because they wanted to put a stronger signal over their cities from a more remote antenna location. So now, if they wanted to go back to a non-directional pattern, they probably couldn't. So it sounds logical that the reason CBW slightly drops power at night is because they moved their original antenna.

 

[Schroedingers Cat]

Under the treaty, a Class I-A, I-B, or present Class A station is only protected to the border of the country of origin. So CBW's coverage stops at the 49th Parallel of Latitude over much of Canada. They use the old skywave model graph for prediction under the treaty however, so even though it is much closer to the Magnetic North Pole, it gets full "750 Mile" protection within Canada. The station on 990 in Ypsilanti, Michigan was allowed to go fulltime with 250 watts, but has to protect CBW with a three tower array at night. In the past, daytime stations had to protect the whole Canadian border with no more than 5 uV/m daytime. Now, the 0.1 mV/m daytime groundwave contour is protected, as well as treaty defined Critical Hours skywave protection, which is 1.5 hours after sunrise and 1.5 hours before sunset.