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cm3020prob said:
In the case of Montreal, CBS (22) is next to CBC (21), NBC (14) is next to Global (15), which I get no reception during the day. Fox (43) operates at a lower power than CBS and NBC so it can be difficult sometimes, ABC (13) is next to CTV (12) but it's at very low power, as in, forget it. But I get PBS-57 (38) and PBS-33 (32) without any problem as they have no co-adjacent channel problem.
cm3020prob said:
If the american RF signal is far but strong enough, placing their transmitter on a RF channel next to the american one will make it difficult to receive.
Assuming that they are both DTV stations, the ATSC standard has dramatically reduced ACI (Adjacent Channel Interference) from the bad old days. The best proof of this I can think of is in Seattle where KOMO on 38 and KIRO on 39 have side-by-side towers pumping out about a megawatt each.

In your case though other interference sources may have an additive effect on the distant U.S. stations. Your own Montreal reception problems with adjacent channels has almost everything to do with your location in relation to those U.S. stations, so we can carry this on in your local reception thread as required but not in this present thread. :)

As for Shaw's reasoning for its choice of potential channels, I agree with the assessments here.
 

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Stampeder, in your Seattle example, both stations are broadcast from a similar location with a similar power so it isn't comparable. With ATSC, adjacent channel interference becomes a problem when there is a large difference in received power. Optimally the frequency plan should be overhauled to have all the stations from the same or nearby towers use sequential channels with similar ERPs.
 

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The problem I was trying to explain was this:

Graphic:
CH14, 650 kW ======> 82 miles ======> home <== 5 miles == CH15, 8 kW

Textual:
CH 14 (NBC) is 82 miles away (130 km) from your home.
CH 15 (Global) is 5 miles away (8 km) from your home.

When CH 15 is not broadcasting (overnight maintenance), you get CH 14 at 50%. Using an amplifier would get a preferable a 75% reception.
Unfortunately, when CH 15 (local) is broadcasting, CH 14 (distant) drops down to 25%. An amplifier will just boost CH 15, that you already receive at 95%, and spread onto CH 14, which drops the signal to 5%.

For Ottawa, you guys told me that it's difficult but not impossible to receive WNPI (PBS) which broadcasts on CH 23 (40 kW), but unfortunately, CHCH-DT-1 broadcasts on CH 22. WNYF-LD (Fox) is apparently using the same tower using CH 18 (4 kW), but CITY-DT-3 broadcasts on CH 17.

I admit, Global using CH 14 in Ottawa might be a long shot but looking at the contour, it's awfull close from Montreal, and it will be next to impossible for west-islanders to receive WPTZ anymore. Even worse when looking at the TVfool map, where the contour almost overlaps, but reception is still medium and possible. Eventho it's legal, it's not welcomed.
 

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I don't see how 14 from Ottawa will interfere with anyone's reception of WPTZ on the island of Montreal. Aside from the fact that that TVFool does not support your theory (WPTZ receive level on the West Island is WAY more than 15 dB higher than ANY Ottawa UHF station), don't forget that until last August 31, channel 14 used to be used for 1.5 MW analog station in Herberts Corners, which is much closer to the West Island than Global's proposed new station at Camp Fortune. I don't believe there were any issues at that time with channel 14 interfering.
 

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I totally agree with tvluker. That is what I have been trying to say. On top of that, any antenna in Montreal pointed towards WPTZ will have much less gain on signals from Ottawa (how much depends on the angle and the antenna).
 

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I lost PSIP EPG data yesterday on 6.1 Ottawa, but strangely enough not on 41.2 (the SD version) Ottawa.
I noticed yesterday Global Toronto's EPG was back to normal. May have been fixed earlier in the week (?)
 

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tvlurker said:
I don't see how 14 from Ottawa will interfere with anyone's reception of WPTZ on the island of Montreal. Aside from the fact that that TVFool does not support your theory
Beyond the island of Montreal, way west... Salaberry-de-Valleyfield, Saint-Polycarpe, Sainte-Justine-Station. Using TVFool's "Callsign Lookup", you can see that reception is medium in that area, so it's possible, then goes purple (very weak) from the Quebec/Ontario border.
Next, open 2012-0465-1, Estimated Contours PDF. The red contour almost reaches the Ontario/Quebec border. Since we know that signals go beyond contours, depending on terrain, and that Global MAY want to boost CIII-DT-6's power someday for more ATSC-M/H coverage, it will create interference, someday, somehow. But as of now, with proposed power, it's borderline. Global should take another channel number that will allow them to expand.
 

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Is it possible to receive WUTV Buffalo or WPTZ from Ottawa? Maybe, in tropo conditions. Moving CIII-DT-6 Ottawa to RF 14 will just make it impossible for Ottawa residents,
I admit, Global using CH 14 in Ottawa might be a long shot but looking at the contour, it's awfull close from Montreal, and it will be next to impossible for west-islanders to receive WPTZ anymore.
Beyond the island of Montreal, way west... Salaberry-de-Valleyfield, Saint-Polycarpe, Sainte-Justine-Station. Using TVFool's "Callsign Lookup", you can see that reception is medium in that area, so it's possible, then goes purple (very weak) from the Quebec/Ontario border.
First you say WPTZ won't be receivable in Ottawa (which we said it isn't currently). Next you say it won't be receivable on the West Island (which we depute). Now you say that you didn't mean west island but way west of the island. What is the real issue you have?

For fun though, I did TVFool analyses on those three towns (assuming 30 foot antenna) and found the difference between WPTZ and the strongest Ottawa UHF channel was as follows:
Code:
Salaberry-de-Valleyfield 42.2 dB
Saint-Polycarpe          30.2 dB
Sainte-Justine-Station   16.3 dB
So things might be getting close for Sainte-Justine-Station, but if you consider there is 153 degrees of separation, the difference in antenna gain will be substantial.


Next, open 2012-0465-1, Estimated Contours PDF. The red contour almost reaches the Ontario/Quebec border.
The noise limited contour falls just short of Alexandria, ON which I guess is getting close to the Quebec boarder. Not so sure what is so magical about that boarder though, considering we are talking about an American station.

Since we know that signals go beyond contours, depending on terrain, and that Global MAY want to boost CIII-DT-6's power someday for more ATSC-M/H coverage, it will create interference, someday, somehow.
Quite frankly I think they have applied for the maximum they can get and won't be permitted more. If they (or anyone else) want more ATSC-M/H coverage, more power isn't the answer, but additional transmitters.

But as of now, with proposed power, it's borderline. Global should take another channel number that will allow them to expand.
What channel do you propose? Channel 6 has already proven to be a poor option (no surprise there as VHF-LO has been very problematic in the US). CBOFT recently took channel 33 since people were having issues receiving it on 9 (even though VHF-HI is much, much better than VHF-LO). Channels 10 and 12 would cause even more problems, since they are used in Montreal. That only leaves 50, which has even further constraints due to co-channel issues with WWTI Watertown (which is much closer than WPTZ).
 

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Leaving protection issues aside, if you have ever studied a realistic propagation prediction for WPTZ (TVfool is close enough, even though it is only Longley-Rice and not one of the more accurate tools), you will see that reception in most of eastern Ontario of WPTZ is shaded by Covey Hill in Southwestern Quebec. So reception of WPTZ west of the Quebec border is problematic already.

As far as Global goes, if they did care about more reliable reception in that small reception hole between Ottawa on channel 14 and Montreal on a low power channel 15, they would look at higher power options for Montreal. If they want to spend money on a new antenna, there certainly are higher power options (like 36). Other options would be a fill-in transmitter near Cornwall. Note that such a transmitter was approved years ago, on the proviso that Global apply for a different channel (they had applied for channel 11, which went to CHCH in Ottawa instead. They never reapplied for a new channel for Cornwall -- instead, they eventually partnered with TVA to take over CKMI Quebec City and put in relays in Sherbrooke and Montreal to create what eventually morphed into Global Montreal.)

But realistically, Shaw Media will have their hands full planning and paying for their commitment to replace all the existing analog transmitters with digital ones. Given that Global's Ottawa and Montreal coverage will both be drastically improved over what they previously had on analog*, trying to minimize the (decreased) lack of coverage in a relatively lightly-populated previously not-covered area between the two cities in not likely to be high on the priority list.

It is also interesting to note that, with channel 14 Foymount likely to stop broadcasting on July 31, the increased coverage on channel 14 to the west compared with channel 6 will give Shaw Media more options when replacing the Denbigh (nominally Bancroft) transmitter on channel 2 in the next few years.


*if you were worried about reception in Prescott-Russell and the United counties on channel 14, imagine how little coverage they had when they broadcast low power on channel 6 when CBC Montreal was broadcasting with 100 kW, to say nothing of the minimal power they used on channel 46 in Montreal, which barely covered the Island!
 

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Good points tvlurker, though I think you mean that Global's Ottawa coverage will be drastically improved over what they previously had on analog. What they have right now is much worse as before the analog shutdown (although the picture on analog 6 may not have been perfect for everyone).
 

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Good points tvlurker, though I think you mean that Global's Ottawa coverage will be drastically improved over what they previously had on analog. What they have right now is much worse as before the analog shutdown (although the picture on analog 6 may not have been perfect for everyone).
Thanks, Roger. I edited workding to show that I meant that the proposed channel 14 is much better than the previous channel 6, but as you say, my experience is that Global's analog signal on channel 6 may have been receivable with rabbit ears, but it was rarely pleasant to watch. The digital signal (where it works) is great.
 

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Keep in mind the reality on the ground vs what we see on the rf6 map is night-and-day. People have trouble getting rf6 in Orleans - even with VHF antennas.
 

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OK, fair 'enough. I do agree that RF14 will improve reception significantly, with the proposition, it will work... but I still think it's not the best channel number, for the sole purpose that if they want to increase power in the near future, they won't be able to do so without creating interference.

When I check on wiki, many US transmitters on UHF band are somewhere between 200 kW and 1 000 kW, while the majority of Canadian digital transmitters are low and medium power since the transition. For example, Buffalo ABC (358 kW), NBC (480 kW), CBS (790 kW), Fox (1000 kW), CW (1000 kW), while Toronto CBC (107 kW), Global (100 kW), Citytv (21 KW), Omni (22 kW)... Canadian networks will either want to increase power to allow mobile/handlet services (and more revenues), or keep them low power just so they can keep their simsub rights.

I'm shooting in the dark here (assuming everything is at Camp Fortune, which isn't true), but Global could share an antenna with an existing co-adjacent number, like 16 or 18 with CITY-DT-3, 23 with CHCH and/or TVO, 28 with Omni.1, 29 or 31 with CIVO, 33 wih CFGS, 41 with CHOT and/or CITS, 44 with CHRO, or anything beyond that seems to be empty for now...
 

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OK, fair 'enough. I do agree that RF14 will improve reception significantly, with the proposition, it will work... but I still think it's not the best channel number, for the sole purpose that if they want to increase power in the near future, they won't be able to do so without creating interference.
Really, the coverage with 160 kW from the top of the tower on channel 14 will be miles better than they had with 50 kW from the bottom of the tower on channel 6.
When I check on wiki, many US transmitters on UHF band are somewhere between 200 kW and 1 000 kW, while the majority of Canadian digital transmitters are low and medium power since the transition. For example, Buffalo ABC (358 kW), NBC (480 kW), CBS (790 kW), Fox (1000 kW), CW (1000 kW), while Toronto CBC (107 kW), Global (100 kW), Citytv (21 KW), Omni (22 kW)... Canadian networks will either want to increase power to allow mobile/handlet services (and more revenues), or keep them low power just so they can keep their simsub rights.
The regulatory and industry environment is different here. The American stations are not owned by BDUs, and moreover, the FCC has a "use-it-or-lose-it policy with respect to allotted powers. In Canada, this only applies (so far) to FM stations, which is why over the past year you've started to see some FM stations increase their power.

You quote some high power Buffalo area stations, but you don't mention that, locally, WWTI ABC Watertown is 25 kW, the PBS stations are 40 (WNPI), 55(WCFE), and 60(WPBS) kW.
I'm shooting in the dark here (assuming everything is at Camp Fortune, which isn't true), but Global could share an antenna with an existing co-adjacent number, like 16 or 18 with CITY-DT-3,
16 is allotted to Watertown, and would require FCC agreement.
18, while currently used by an unprotected LP station from South Colton, is actually allotted in the international agreement as a full-power (30kW) station at South Colton.
CITY is at Herberts Corners. Even if Global moved there, it could not use more than 51kW adjacent to a 5.1 kW station according to the rules in BPR-10.
23 with CHCH and/or TVO,
23 is WNPI South Colton! In any case, you can't simultaneously be adjacent 22 at Herberts Corners and 24 at Camp Fortune.
28 with Omni.1, 29 or 31 with CIVO,
These might work, but I'm not sure how high you could go in power. They are currently low power allotments in Cornwall.
33 wih CFGS,
This would have been a good choice, but CBC grabbed it first! (And they own the tower)
41 with CHOT and/or CITS,
again, you can't straddle CF and HC that way.
44 with CHRO, or anything beyond that seems to be empty for now...
Some of these other higher number channels are allotted to adjoining areas, like Arnprior and Smiths Falls. There is also a high power open allotment on 50 at Herberts Corners.

The bottom line is that there is a fear that 31 and up will be abandoned, which makes any high power available spot below 31 much more feasible in the long term. 14 is probably the best bet, given that it was already used here during the pre-transition phase. The only other possiblity would be 19, but then it would have to be very low power (to protect SRC Montreal) and at Herberts Corners (adjacent to OMNI2 on 20). And frankly, that would prevent more people in the Ottawa area from getting WNYF on 18 than being on 14 would interfere with WPTZ on 14.

Personally, I think the cheapest bet would have been to reuse the existing channel 9 antenna (if Camp Fortune Tower's owner CBC would allow for it) at 20 or 30 kW, but that would still not be good enough for mobile-ATSC use.
 

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I already adjust low-VHF signal levels down on my maps by 13 dB from where official projections put them, and really even that isn't enough!
True, it isn't enough. I read that the FCC says VHF-HI needs 10dB more power than projected and VHF-LO needs greater than 20dB more power than projected (more power than practical). The biggest problem with VHF-LO is indoor reception. Modern houses are filled with impulse noise (and it is only going to get worse), which is known to cause problems with VHF-LO reception but has no effect on UHF. Outdoors, not only is the signal stronger, but your antenna is shielded from all that impulse noise generated inside. As a result, you could probably keep the noise limited contour for VHF-LO about the same but reduce the urban contour by 20 or 30 dB (on the map I would have the urban contour include the old cities of Ottawa, Nepean and Gloucester, but exclude Kanata and Orleans).

It might be possible to design ATSC tuners that better deal with impulse noise, but since the vast majority of the testing was done on UHF, they never considered it a problem. Now the market has already been flooded with the current generation of tuners, there is no incentive to fix the problem (especially since most markets don't use VHF-LO anymore).
 
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