: Global Ottawa DTV Transition - Aug. 16, 2011 - update in Post #331


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tvlurker
2011-08-25, 11:33 AM
That's what I'm wondering... can you really get a license for a local broadcast station and only pump out a few watts on VHF-lo and instantly expect full regional BDU carriage regardless??


Yes, because the theoretical contours are quite large. To get priority cable carriage status, only the headend needs to be covered.

Yes, in theory they need to cover the city of license, but according to the coverage contrurs, they do.

There is still room for a complaint, since experience trumps theory.

And, if not, can Global TV be pushed (via CRTC) to take action (higher power and move to UHF) based on this?

Certainly Global would have grounds for applying for a change. Whether the CRTC can force them to is a good question.

Not to mention Global TV is probably claiming to advertisers viewership numbers including regional OTA users.
How many OTA users get BBM diaries? I think that's where the 7% or 10% OTA number comes from.

flavoie
2011-08-25, 01:53 PM
These contours must be based on assuming each subsriber is using a large outdoor directional VHF antenna, 30 feet high on a tower.

Could someone point me to the Global Ottawa application ? I would like to look at it. I bet it this is what it mentions in one of the assumptions for antenna/receiver gain on the CPE side.

Dave Loudin
2011-08-25, 03:03 PM
I posted a link to the methodology used by the FCC and the CRTC for making DTV allocations in another thread. Search for OET-69. You will not see the assumptions in every application because it is always the same.

The upshot is there was an error in the power density assumptions for VHF-high of 10 dB or so, and likely more for VHF-low. Broadcasters had to use this model in applying for new facilities, so it's not completely their fault. Any allocation contour (my phrase - they are a first approximation for coverage) you see will still use this flawed approach.

As I've stated before, stations will have to show how their results depart from predictions in order to ask for more power (there's the matter of not creating interference to others.) I've linked to filings of US VHF stations to show examples (search for WUSA).

tvlurker
2011-08-25, 03:40 PM
You can find the document BPR-10 Application Procedures and Rules for Digital Television (DTV) Undertakings (http://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/bpr10-i1.pdf/$FILE/bpr10-i1.pdf) Canadian stations need to follow on the Industry Canada Spectrum Management website.

C-2.7.2 A map showing the noise-limited bounding contour and the digital urban contour shall be provided. For further details concerning the preparation of maps for engineering briefs, refer to Section 3 of BPR-1.
Maps may be provided indicating the protected areas and interference for the proposed assignment and any other affected assignments or allotments (refer to Section C-6.2).
When a change to the facility is proposed, the applicant shall provide maps indicating comparative contours.
Part 10: Application Procedures and Rules for Digital Television (DTV) Undertakings BPR-10
12
For applications using associated allotments, the applicant shall provide a map showing the noise-limited bounding contour and the digital urban contour of the proposal and the Grade A and B contours of the corresponding analog undertaking (CRTC requirement).
C-2.7.3 The latitude-longitude geographical projection and the datum NAD83 shall be used. The Department is not supporting datum NAD27 and will only consider NAD27 if it is justified and warranted by special circumstances.
C-2.7.4 In cases where proposed television undertakings are located in areas of mountainous terrain or in the proximity of other natural obstacles, an additional analysis may be necessary to show the protected area as defined in Section B-1.6. For such cases, the calculation of the field strength should be based on a terrain-sensitive method, e.g. the Longley-Rice model or PREDICT 2.08r2 software, using the appropriate time and location statistics.

I looked at the app for channel 6, and it's pretty scant on details.
The Engineering Brief that the broadcaster submits to Industry Canada to get a broadcast certificate is NOT a required part of the CRTC application for a broadcast licence. However, colour coverage maps are, and often this requirement is met by including the entire Engieneering Brief in the CRTC application. In many other cases, just the coverage maps themsleves are submitted to the CRTC.

And while I was poking around, I found the DTV converter box standard as an appendix to BETS-7 - Technical Standards and Requirements for Radio Apparatus Capable of Receiving Television Broadcasting (http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf01229.html#annex)

tvlurker
2011-08-25, 03:44 PM
These contours must be based on assuming each subsriber is using a large outdoor directional VHF antenna, 30 feet high on a tower.

True, but the real question is do viewers at the Noise-Bounded contour with a VHF antenna 30 feet in the air actually receive this station?

If they did, then one would think that those within the urban contour whould be able to use an indoor antenna.

Dave Loudin
2011-08-25, 05:40 PM
^^^^^
If we are talking UHF, in general, the answer is yes. Remember that these contours are statistical abstracts. Point-to-point Longely-Rice calculations would provide a better answer to this question. Because of the errors in the VHF calculations, the contours are off for that band.

BTW, the gain assumptions are:
Low-VHF: 4 dBd
High-VHF: 6 dBd
UHF: 10 dBd

Antenna height: 30 feet

Dave Loudin
2011-08-25, 06:11 PM
The complete planning factors for DTV, as found in Appendix 8 of the IC's BPR-10 are:

Planning Factor | Symbol | Low VHF | High VHF | UHF
Geometric Mean Frequency (MHz) | F | 69 | 194 | 615
Dipole Factor (dBm-dBμV/m) | Kd | –111.8 | –120.8 | –130.8
Dipole Factor Adjustment | Ka | None | None | See Text
Thermal Noise (dBm) | Nt | –106.2 | –106.2 | –106.2
Antenna Gain (dBd) | G | 4 | 6 | 10
Downlead Line Loss (dB) | L | 1 | 2 | 4
System Noise Figure (dB) | Ns | 10 | 10 | 7
Required Carrier to Noise Ratio (dB) | C/N | 15 | 15 | 15

These go into the equation: Field (dBμV/m) = C/N – Kd – Ka – G + L + Nt + Ns

The adjustment, Ka = 20 log[615/(channel mid-frequency in MHz)], is added to Kd to account for the fact that the field strength requirements are greater for UHF channels above the geometric mean frequency of the UHF band and smaller for UHF channels below that frequency.

wing
2011-08-25, 08:30 PM
So I picked up a 302sr and a cm7777. Mounted the antenna on the roof about 35' up. Pointed it at CF. pointed my CM4228 at HC roughly, maybe not even. I now get the elusive 66-1 OMNI2. Which I could not get at about 75% signal.

But Global no dice!!! I'm so POed! My analog VHF channels are clearer for sure. I've tried three tuners with no luck. Actually before I put up the 302 mt Myth found 6.1 but couldn't lock, now it said it locked during the scan on 6 but no channels were found.

Is global working today? Maybe I'll have to adjust my positioning but it's pretty close, I'm only 19miles away this is ridiculous!

becks
2011-08-25, 08:33 PM
^Global has worked perfect all day. Where are you located?

PanaMark
2011-08-25, 08:53 PM
Why do you people down in Ottawa continue to insist on the strongest preamps, ie:CM7777 in such a high signal area? You can't have the best of both world's.
I understand that you want fringe signals, ie: PBS and so on but I strongly suggest trying the preamp further away from the antenna. VHF dB losses on an 25 feet of RGF6 are next to nothing.

I just find it so hard to believe that a trusty VIP 302SR cannot pull in RF6 within 6o miles. I am beside myself on this one.

stampeder
2011-08-25, 09:05 PM
Thanks for using this thread to keep our members informed of the latest situation with Global Ottawa's DTV transition. Great job!

It was opened as a special case so that the existing OTA Station Status: Ottawa, Watertown NY, S. Colton NY (http://www.digitalhome.ca/forum/showthread.php?t=107973) thread would still be readable for news regarding the technical and operational status of other stations, but now that about 10 days have gone by since Global Ottawa transitioned let's get back to using that original status thread, and of course remember to use one of the several Ottawa-area local reception results threads that best applies to your location.

Remember: Station Status threads are only for the technical and operational status of stations but not about your own local reception or your OTA gear. Use your local reception results thread for those topics.

cheers :)