junior6, I think you'll find with some reading through this forum that Industry Canada sets the output power of DTV stations in Canada. I don't like the numbers either, but we're stuck with them.

junior6, I think you'll find with some reading through this forum that Industry Canada sets the output power of DTV stations in Canada. I don't like the numbers either, but we're stuck with them.

I believe that Industry Canada has the authority to assign a channel class and to approve or disapprove a station's requested power based on interference.

CIVT-DT is listed as a class C channel in the digital allotment plan. They are allowed to broadcast with up to 15 kW of power during the digital transition (present constraint) and up to 75 kW post digital transition.

The interference is much harder for us to determine. There is an analogue channel - KWPX Bellvue - broadcasting on channel 33. KWPX also broadcasts on digital 32 which would cause some interference. It would take a broadcast engineer with the correct tools to determine if CIVT can raise their power and still prevent interference. If interference was a significant problem holding back their digital broadcast power they could have requested a different channel.

I have a suspicion that they could broadcast with a higher power, but have chosen not to. Looking at their application for digital transmission, their map shows most of Greater Vancouver covered by their signal. This is enough to protect their simulsub rights for cable and satellite.

I believe that Industry Canada has the authority to assign a channel class and to approve or disapprove a station's requested power based on interference.Yes, that's the essence of it but a station cannot arbitrarily change its power. An application must be made to the CRTC, which will decide on whether to approve the change to the station's license.

ardsa and junior6, this following link is to the Understanding OTA DTV Broadcasting Technology in Canada thread that is packed with information on the topic of broadcasting licenses and power levels:

http://www.digitalhomecanada.com/forum/showthread.php?t=25774

We'll now return this thread back to its Vancouver/Victoria/Bellingham OTA DT Station News topic. :)

The interference is much harder for us to determine. There is an analogue channel - KWPX Bellvue - broadcasting on channel 33. KWPX also broadcasts on digital 32 which would cause some interference. It would take a broadcast engineer with the correct tools to determine if CIVT can raise their power and still prevent interference. If interference was a significant problem holding back their digital broadcast power they could have requested a different channel.

I am sceptical of the interference argument. As you rightly say, KWPX Bellevue are allocated the same channels as CIVT, but with the analogue and digital swapped. This station is also transmitting digital at full power and so, using the interference argument, could interfere with CIVT Ch32 analogue in some areas of BC. However, viewers towards the northern coverage of KWPX around Mount Vernon will have large antennas pointing south and any interference from CIVT-DT will be coming in on the back of the antenna. Because the antenna concentrates its signal receiving in the forward direction, it has a reasonable ability to reject signals coming in the back of the antenna. The signal strength from CIVT-DT would have to be a maximum of 1% (1/100th) of the signal from KWPX for Mount Vernon viewers to have a clean analogue signal from KWPX. Given the present power level from CIVT-DT, I have to wonder whether it even reaches the US border, never mind as far as Mount Vernon. Perhaps any forum readers south of the 49th parallel can let us know if they can pick up CIVT-DT, Ch 33.

By the way, does the digital transition to high power relate to the US shutting down analogue or the Canadian? There would be nothing wrong with full power digital in the case of CIVT-DT even before Canadian analogue shutdown if the interference argument related to the KWPX analogue.

There is the adjacent channel interference argument which more relates to older TV sets and converter boxes where the selectivity was not as good and an adjacent channel could produce interference patterns. But, I don't believe this is a valid argument anymore.

However, like you, I see the ultra low power of CIVT-DT as the thin edge of the wedge to help the CRTC argument for not going HD OTA and steering viewers into the clutches of the cable and satellite companies.

Further to my previous response, I have been doing some calculations. It does indeed seem that the CIVT-DT power level is at 319 Watts ERP to prevent interference to KWPX analogue in its outer coverage area around Mount Vernon about equal distance from both transmitters. Here is the maths.

CIVT-DT 319 Watts
KWPX 3720 kW

Ratio of power level = 3720/0.319 = 11661.44. In dB this is 10 log 11661.44 = 40.67 dB. This is the amount by which the KWPX signal is stronger than CIVT-DT at a mid-point between the transmitters.

To not produce interference on an analogue transmission, the wanted signal has to be 53 dB stronger than any interference. If the front to back ratio of the viewer receiving antenna of at least 12 dB is factored in, then we come close to the 53 dB value.

So, even though 319 Watts cannot even cover some areas of the Lower Mainland, it is the maximum power level directed south-eastwards that can be used so as not to interfere with KWPX analogue. Possibly more power from CIVT-DT could be radiated in other directions.

impressive use of math Rick! I asked CTV why they were so low and they said it was just enough to cover the same footprint and not cause interference both with CIVT-TV 32, and KWPX-TV 33. Personally, I don't see why CTV or KWPX could have picked a channel so that this conflict with the other station wouldn't exist. I suppose there's nothing they can do about their analog channel designation but they could have applied to have their digital channel changed to something else. Didn't CHEK-TV change their would be digital channel?

Plus, don't you feel that Canadian ERPs aren't decent because US stations have already got high ERPs. We cater to them, not the other way around. I guess that's what we get when you snooze you lose. Thanks CRTC! :)

As I said in a previous post, I don't believe the argument about interfering with CIVT-TV 32. Modern TV sets can deal with adjacent channels pretty well and CIVT-DT would only need 5% of the analogue transmitter power level for equal coverage with CIVT-TV.

Industry Canada in conjunction with the FCC in border areas allocates the channels - the stations have little to do with it. Possibly Ch 31 could not have been chosen instead, but there is KONG-DT Everett on that channel. The higher power levels could have been used for CIVT-DT if this channel were used as it would not be co-channel with an analogue transmission. Don't know off hand how much stronger the digital signal has to be versus an unwanted signal.

Where possible, for a station the digital channel is chosen close to the analogue channel to reduce equipment costs (the same antennas can be used along with some equipment) especially if the station will be reverting back to the analogue channel after analogue shutdown.

If there is still going to be DT OTA, for my 10¢ worth I think all the digital transmissions should be on the UHF and ideally from the same site. Then one neat UHF antenna could be used.

Complicating matters for CHEK-DT Victoria was that ongoing talks have been happening regarding eliminating the 60-series UHF channels except for specific emergency broadcast channels. Thus their originally assigned channel selection became really awkward for IC and the FCC in such an adjacent metropolitan border area.

Things are deteriorating for me. Signal strength on CIVT-DT dropped from ~66% to < 60% on my ATI HDTV Wonder, making it all but un-watchable. Have you noticed that on your TV as well?

I dived into OTA with the expectation of Global coming on-line, a stable CBC and CTV feed and hopefully cutting my monthly cable bill. But hope is fading fast.

Mike, you're so right!! I've got line of sight eh, so I always had CIVT-DT pretty strong. It usually comes in at 87-89% @ 27dB (and was like that, last time I checked was about a week ago), now it's at 73-76% @ 22dB.

They have definetely lowered the ERP, or must be doing some broadcast tests. Unlike you, I've still got a digital lock, but like you I'm not impressed. I didn't think 319watts was enough, but they must have lowered it even more, as nothing has changed on my end, nothing is blocking my view, so ERP or directional modification is the only explaination.

They've got a class C transitional licence, they should max out that ERP limit for their HAAT, to an ERP of 30.4kWatts. I've also done some math to calculate what I think they'd need for a digital ERP to match the footprint of their analog signal. CIVT-TV's ERP is 710kWatts @ 32UHF (581Mhz). When you factor in the jump to 33UHF (requiring a little more power) you get a factor of 1.01x. 710,000 * 1.01 = 717,100watts. And we'll be generous and say that DTV requires 10times less ERP to cover the same footprint, so take 717,100 / 10 = 71.7kWatts. THAT's the kind of power I want to see in it's final stage (which would require a VU class license).

Phone CIVT and tell them that their signal is low AGAIN. This isn't the first time its dropped, and last time they said it was a "failed power module" or something like that.

Thanks for the confirmation and the advice.

I emailed them this time. I'll phone if it happens again, or isn't fixed soon. Geez, what ungodly ERP are they broadcasting at now!? I mean, you can't get much lower than 319watts!

CIVT-DT is back up to full power, if you want to call it that ;)

CIVT-DT is back down to "even lower power". Check your signal strength. Mine's back down to what it was last time it was lowered. 76%

I would expect that if their OTA broadcasting gear is working improperly they'd have alarms going off or their monitoring would be showing problems and they'd fix it promptly. Ya never know though...

I cut and pasted this map out of a free NASA satellite composite image. It gives an excellent view of geographical relief and topographical features that affect DTV reception in Canada from SeaTac and Bellingham stations:

http://www.user.dccnet.com/jonleblanc/images/Van-Vic-SeaTac.png

Good DXing coming up for the Island and the Lower Mainland! :)

http://www.digitalhomecanada.com/forum/showpost.php?p=398908&postcount=96

any email for general dtv inquiries for ctv?

my signal isnt too great after testing for a few days...sometimes its ok but most times it seems like im 'almost' getting it locked in...maybe an amp would help..im not sure...

Go to their web site and look for the "bcengineering" email address on the Contacts page.

http://www.bcctv.ca