OTA ERP Levels (Analogue vs. DTV) - why so different? - Page 3 - Canadian TV, Computing and Home Theatre Forums

Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #31 of 97 (permalink) Old 2010-10-21, 11:19 PM
Veteran
 
Join Date: Feb 2009
Location: The Dandelion City
Posts: 7,131
But there would then be groups of channels on UHF that are free for neighboring markets. The current system is not without problems either. There are some markets where channels are on alternating frequencies (due to historical analog adjacent channel interference) and on the exact same frequencies in another market not far away. The current system is a mess. There is too much duplication of resources at both the broadcaster and consumer end. In Britain, digital stations in each market are grouped on adjacent channels and broadcast from the same site. (Think CN tower like facility with channels all near the same frequency.) That makes it much easier for consumers to set up an antenna and receive all stations in a particular area. Antennas can also be tuned for peak reception performance for a certain area.

The Canadian situation is a disaster for consumers in many areas. For example, we have CTV on VHF-hi in one direction, Global on VHF-lo in another, /A\ on VHF-hi in yet another. CITY, CH, TVO and CBC are all in different directions on the UHF band from channels 18 through 51. What a difference it would make if they all were between UHF 14 and 30 on the same tower.

At 20 I had a good mind. At 40 I had money. At 60 I've lost my mind and my money. Oh, to be 20 again. --Scary
ScaryBob is offline  
Sponsored Links
Advertisement
 
post #32 of 97 (permalink) Old 2010-10-28, 02:47 PM
Veteran
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 3,395
Quote:
Originally Posted by roger1818 View Post
Isn't this only true for UHF? I gather that post transition in the US they discovered that VHF-HI requires about 10 dB more power than anticipated and VHF-LO requires 15 to 20 dB more power than anticipated.
Recent "findings on the ground" finally forced the FCC to reconsider their "assumptions" re VHF.
Part of the problem has been a dearth of (believable/repeatable/comprehensive) data re
Man-Made Impulse Noise,, esp. it's effect on DTV and "Land-Use and Local Clutter (LULC)" Clutter Loss.
And the FCC's reliance on old ANALOG experience re requisite signal levels....but Digital is apparently
MORE susceptible to Impulse Noise (long glitches) than Analog (small visual defects).

On the other hand, recent ATSC Tuners have dramatically IMPROVED the ability to handle
Multipath, compared to the tuners used in ALL of the earlier On-Air tests.....so the 15 dB SNR
"minimum" for ATSC is probably closer to REAL OTA in current tuners (+/- 2 dB), whereas
earlier tuners might need 2-5 (to infinity) more SNR, depending on local multipath conditions.
I've seen some "Brazil" Multipath On-Air capture tests succeed with less than 15 dB SNR,
indicating that the Multipath components were being coherently combined. If two equal
strength signals (each at 12 dB SNR, with multipath delay between them) is coherently combined,
they could act as one signal at 15 dB SNR. [Hence F/B Ratio not as important to counter multipath???]

BTW: FCC OET-69, "Longley-Rice Methodology for Evaluating TV Coverage and Interference"
ignores BOTH of these important factors, although it is described in detail in FCC OET-74,
"The ILLR Computer Program", stipulating ZERO correction for VHF and typically 7 dB correction for UHF.
But both ASS-U-ME the Thermal Noise floor is never exceeded.......[cough....cough.....]

Here is what the FCC said about "Urban" (Man-Made Impulse) Noise in FCC-00-185 (22May2000):
"Additionally, several parties recommend that we modify the ILLR model to account for urban noise
on the basis of the measurements of noise included in the Rubinstein report. However, we believe these
are matters of signal quality rather than intensity. In this rule making we are concerned with the ability
of the ILLR model to predict the availability of signals of a specific intensity as directed by Congress,
and we decline to extend the scope of the issues addressed in this proceeding to include signal quality."


But Rubinstein only tested LULC on 162, 460 & 860 MHz and Urban Noise on (only) 162 MHz in four
locations (NO data for Lo-VHF).
http://ieeexplore.ieee.org/xpl/freea...rnumber=715314
Clutter Loss ranged from 10 to 17 dB on BOTH 162 and 460 MHz, but measurements were incomplete.
"Environmental" Noise on 162 MHz was 11-16 dB above Thermal Noise in Watcom County, WA and Atlanta, GA,
rising to as high as 18 dB above in the Southern California (L.A. & San Diego) areas.
[Note that Rubinsteins's results conflicted with several other similar LULC tests!!!!!]
[They reported several problems with data collection, tossing out lots of suspect data.....]
[No statistics re Noise levels....are they Average....or Peak....or something else.....]
[And their choice of 162 MHz is not explained....perhaps Noise included BAND USER signal levels???]

It is well known that VHF Man-Made Impulse Noise can be 10-40 dB HIGHER than the
Thermal Noise Floor, increasing towards the lowest frequencies, as depicted in Figure 10,
ITU-R Rec P.372 Noise Charts (former CCIR 322, apparently STILL ignored by FCC's OET Group):
http://www.itu.int/rec/R-REC-P.372-10-200910-I/en
Yikes, ITU wants 40 Swiss Franks for a fraking copy.....so see "Fam" in the fol. Figure 2:
http://www.mstv.org/docs/techinfo.pdf
But how does one calculate a statistical "coverage" for Impulse Noise, when it varies depending
on distance from overhead power & other lines and will also vary from house-to-house, depending
on whether using fluorescent tubes, brush-type motors, dimmers, arc-welders, ad nauseum.
And DURING a nearby lightning storm, each strike will kill nearly ALL reception....

Clear, concise technical arguments were presented re the need for ILLR Propagation Model improvements:
http://hraunfoss.fcc.gov/edocs_publi...C-05-199A3.pdf
Which were argued AGAINST, mostly because they were presented by Dish Network's hired experts,
who were immediately discounted since Dish Network was trying to expand their Network viewers.
[A clear example of Politics trumping Engineering....but avoided very protracted court arguments....]

Ultimately, in FCC-05-199, FCC decided to do NOTHING wrt ILLR changes (avoiding the quagmire):
http://hraunfoss.fcc.gov/edocs_publi...C-05-199A1.pdf
Only recently, did they encourage power increases for Hi-VHF.....
holl_ands is offline  
post #33 of 97 (permalink) Old 2011-02-18, 06:38 PM
Veteran
 
Join Date: Apr 2004
Location: derry + winston Mississauga
Posts: 1,654
CFTO-dt Power Level

TV fool has CFTO-dt pending on channel 9 and its showing a 6db drop from analog 9 level.Clearly CFTO will not be matching analog 9 coverage area.

Attic CM 4248 at Buffalo,M4 at Buffalo.VHF yagis at Toronto .

Last edited by rob50312; 2011-02-18 at 06:38 PM. Reason: spell
rob50312 is online now  
 
post #34 of 97 (permalink) Old 2011-02-18, 07:48 PM
Veteran
 
Join Date: Jan 2009
Posts: 4,612
Hi Rob,
GeorgeMx answered that in post # 15. A good read.
majortom is online now  
post #35 of 97 (permalink) Old 2011-02-18, 08:14 PM
Veteran
 
Join Date: Apr 2004
Location: derry + winston Mississauga
Posts: 1,654
VHF high for ASTC requires about 40 to 60kw to match a full power analog VHF hi .Look at how poorly WNGS signal is performing at 27kw directional North.

Attic CM 4248 at Buffalo,M4 at Buffalo.VHF yagis at Toronto .

Last edited by rob50312; 2011-02-18 at 08:16 PM. Reason: more
rob50312 is online now  
post #36 of 97 (permalink) Old 2011-02-18, 08:42 PM
Veteran
 
Join Date: Jan 2009
Posts: 4,612
Don't ya think that has more to do with WNGS antenna height (HAAT), and that most OTA users aren't using antennas optimised for VHF Hi?
To me all bets are off for fringe reception if the end user isn't willing to use a decent VHF antenna.
majortom is online now  
post #37 of 97 (permalink) Old 2011-02-18, 09:03 PM
Moderator
 
Join Date: Jan 2009
Location: Kitchener, ON
Posts: 5,034
There are more variables at play than just ERP. HAAT and contour for sure.

Roof-top mounted Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection. TiVo Roamio DVR
Jase88 is offline  
post #38 of 97 (permalink) Old 2011-02-18, 09:05 PM
Veteran
 
Join Date: Apr 2004
Location: derry + winston Mississauga
Posts: 1,654
I have 7 element VHF antenna in my attic for years and it could not lock WNGS but received the old 2,4,7.& 7 was perfect.I agree WNGS would be better if they had a higher tower but I think ASTC in VHF, background noise limits reception to LOS.

Attic CM 4248 at Buffalo,M4 at Buffalo.VHF yagis at Toronto .
rob50312 is online now  
post #39 of 97 (permalink) Old 2011-02-18, 09:11 PM
Veteran
 
Join Date: Jan 2009
Posts: 4,612
yup, agree with both of ya.
Maybe get that guy out of the attic and out on the roof instead.
If ur on the verge now, might be enough to get ya over the cliff?
I am pretty certain that I won't be getting CFTO on VHF 9 here when it comes time
next August. Not with all the trash I see around here.
majortom is online now  
post #40 of 97 (permalink) Old 2011-05-29, 07:13 PM
 
Join Date: Dec 2009
Location: Frisco, TX USA
Posts: 192
In anticipation of the transition, are there any plans for stations (particularly those heading back to their current VHF channels) to try a test during the wee hours of the morning on their post-transition facilities?

In GTA, CFTO and CHCH would be of particular interest. Based upon the "VHF Nightmares" here in the US, they seem a tad underpowered. I recall that a handful of stations (such as WHYY in the Philadelphia market) did operate with such tests. It was then that the first realization set in that maybe VHF wasn't going to be the "beachfront property" it was touted to be.
re_nelson is offline  
post #41 of 97 (permalink) Old 2011-05-29, 07:31 PM
Moderator
 
Join Date: Jan 2009
Location: Kitchener, ON
Posts: 5,034
Unlike in the US, most conventional TV stations in Canada view OTA transmitters as a regulatory burden.

Obviously the stations will ensure that their VHF DTV transmitters are functional and operating within their licensed parameters. Though I doubt they'll be doing any sort of coverage testing. And I doubt we'll be seeing any emergency requests for more ERP or changes back to a UHF designation.

Likely the most stations would be willing to do is bump up TX power from average to maximum ERP. Which, in the case of CHCH 11, is 4.5kW to 6kW; and CFTO 7.2kW to 10.8kW.

Roof-top mounted Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection. TiVo Roamio DVR
Jase88 is offline  
post #42 of 97 (permalink) Old 2011-05-29, 10:49 PM
 
Join Date: Jan 2002
Location: Toronto
Posts: 738
Quote:
Originally Posted by Jase88 View Post
...

Likely the most stations would be willing to do is bump up TX power from average to maximum ERP. Which, in the case of CHCH 11, is 4.5kW to 6kW; and CFTO 7.2kW to 10.8kW.
In 8 VSB transmission, there are multiple amplitude levels in the signal with the highest being the peak or maximum ERP. The situation is not unlike analog where the maximum station ERP is sync peak due to the use of negative modulation. Increasing power on the transmitter will raise the level of peak and average ERP which requires authorization from Industry Canada.
GeorgeMx is offline  
post #43 of 97 (permalink) Old 2011-05-29, 11:23 PM
Moderator
 
Join Date: Jan 2009
Location: Kitchener, ON
Posts: 5,034
GeorgeMx, Understood. Though I believe they have some play between their average and maximum allotments here. Perhaps not enough though to make much of a difference...

Roof-top mounted Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection. TiVo Roamio DVR
Jase88 is offline  
post #44 of 97 (permalink) Old 2011-05-30, 12:16 AM
 
Join Date: Dec 2009
Location: Frisco, TX USA
Posts: 192
Quote:
In 8 VSB transmission, there are multiple amplitude levels in the signal with the highest being the peak or maximum ERP. The situation is not unlike analog where the maximum station ERP is sync peak due to the use of negative modulation. Increasing power on the transmitter will raise the level of peak and average ERP which requires authorization from Industry Canada.
GeorgeMx:

Could you explain the peak vs. average ERPs in more detail. Here in the US, the FCC forms show only the actual TPO (transmitter output power) and one value for ERP (expresssed in both dB and kW), reflecting antenna gain.

I take it that IC does it differently. Which of those two ERP values is closest to the one value used here in the states?
re_nelson is offline  
post #45 of 97 (permalink) Old 2011-05-30, 02:02 AM Thread Starter
Premium Supporter
 
Join Date: Jul 2003
Location: Calgary
Posts: 3,741
@re_nelson: Please flip back to Post #15 of this thread for GeorgeMx's original post on this topic.
http://www.digitalhome.ca/forum/show....php?p=1158387
The peak powers being discussed in this scenario have nothing to do with peak power in directional antenna patterns. (Antenna pattern peak/directional power is what the FCC and IC ERP data show us.)
Anyway, I hope I haven't confused things …
downbeat is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome