TVFool Canadian Discussion

[HWP]

I used to think that was frustrating, too, but upon reflection, I came to the same conclusion the TVFool people probably came to --It's probably way too complicated and fraught with other problems to start overruling the FCC and IC databases to correct their inaccuracies in the dozens and dozens of markets they provide information on.

I choose to redirect my frustration to redirect my frustration to the people that deserve it - Industry Canada.

[stampeder]

Between TVFool and RabbitEars one can usually get a good sense of what is out there, but I absolutely agree that the effort required to over-rule the official databases would be unending and heavy. Thankfully Canadians have this site!

[Trip]

Funny that you mention it, because I do hand-manage my Canadian listings to try to make them reflect reality. Not one single Canadian listing on RabbitEars is automated.

- Trip

[alebowgm]

Could you imagine if the map TV Fools gave you was based on the RabbitEars DB. It would be amazing!

[Pierre R.]

Looking at the chart below, the farthest red channel is situated 75 miles away. How likely would I be to receive the channel if I install a 100 mile rated rooftop antenna?

I would love to get the gray channels, but TVFOOL mentions that
they are tough to get. Have you found this to be true?

Any words of wisdom would be appreciated by this newbie.

[Sportfreunde]

The channels in gray are never reliable for me but I am able to pull some of them in with an indoor antenna though it depends on weather and they disappear time from time plus more adjustment is required.

With that outdoor antenna you should expect to get almost everything that's not in grey. However even with an indoor antenna I'm able to pull in most of the channels that are in red for me so it really depends if those grey channels are worth the cost of doing an outdoor installation to you.

The one problem I see for you is that most of the channels in red are above 60 mi so it might be tough to pull those in with an indoor.

[majortom]

another issue is there seems to be several clusters of transmitter locations
in different azimuths.
55, 167, 220, 340 degrees. So ya may need a rotor.
You should also post the general location and height of the proposed receive antenna.

[tvlurker]

PierreR appears to be near Trois Rivieres. There is very little difference other than local news between his local channels, and the ones from Quebec City and Sherbrooke, other than Global (CKMI), which would be too weak to get from Montreal. So he would need a good VHF/UHF deep fringe setup to get CFCF and CBMT from Montreal, and then try for Global on 11 from Sherbrooke or 20 from Quebec City.

[holl_ands]

This was discussed beginning post #14 in this thead, as well as here:
http://www.digitalhome.ca/forum/show....php?p=1383269

Grey means you need an EXCEPTIONAL (perhaps Stacked) Antenna system and
a very low System Noise Figure (e.g. Mast Mounted Preamp). If the NM value
plus the Antenna Gain on that channel frequency minus the System Noise Figure
is in the ballpark of 0 dB, then 50% of the locations with the same situation will
have "minimally acceptable" reception performance.....which is a statistical way
of saying it might work....sometimes....somewhere.....but don't expect it to be
reliable....for reliable reception corrected NM needs to be in the 10-20 dB range.

System Noise Figure can be calculated using Spread Sheet found here:
http://www.digitalhome.ca/forum/showthread.php?t=42426

System Noise Figure also found by adding Balun Loss to following chart value:
http://www.digitalhome.ca/forum/showthread.php?p=888368
Chart assumes an exceptional ATSC Tuner Noise Figure = 6dB.
This is very rare....most are in the range of 7-10 dB, which needs to be
added to the "Gross Transmission Loss" to properly use the chart.
[Unfortunately, you won't find HDTV Noise Figures in spec sheets.]

So don't expect to push reception into the Grey area more than a few dBs
in the negative direction as listed in TVFool results:
http://www.tvfool.com/index.php?opti...d=57&Itemid=89

[roger1818]

Pierre R., a few other comments.

First of all, TVFool can't take into account local factors such as buildings and trees, so reception may be worse than predicted in some circumstances. This is especially true for signals with a 2edge diffraction.

Also, the rating of antennas by "miles" is marketing mumbo-jumbo and should not be relied upon. You are better off looking at its technical specifications (such as gain in either dBi or dBd), though some manufacturers will overestimate those figures.

[Pierre R.]

Thank you very much for the replies, and sorry for the tardy response.

At the time of this posting, I haven't had the time to read the links you provided, but rest assured that they will be read and are greatly appreciated.

In the meantime, here is some extra information some of you have requested:

I am in Trois-Rivieres and am interested mostly in the channels from Montreal which are on the 222* azimuth. Being that it is the St.Lawrence lowlands, it is very flat terrain. The nearest thing on that azimuth is a two story house about 200 meters away followed by more two story houses and 40-60 foot trees for several kms. The antenna could be mounted 20-30 feet high.

I'm pretty handy so I would build the tower myself (probably a boom type thing that could be easily lowered for occasional de-icing).

I had initially figured $150 but wouldn't mind paying $200-$300 IFF(remember that from math class) it is worth it.

[envirogeek]

Speaking to TV Fool interpretation directly, all of my 7 Edmonton area stations are 2Edge, red or grey.

I am using a UHF bow tie antenna covering an arc of 37 degrees, receiving signals from 4 broadcast towers at distances from 34.1 to 45.5 miles.

My weakest channel by NM using a 30 foot AGL entry in TV Fool is -24.5. My weakest channel in real life reception has a reported NM of -1.7. This channel is most subject to the occasional drop out due to the trade offs of aiming which put that particular channel at one extreme of the arc of my antenna.

I could not pick up the High VHF channels reliably until I increased the height of my antenna from approximately 20 feet to around 30 feet.

With the TV Fool information you really have to focus on the channel(s) that are most important to you.

[roger1818]

envirogeek, how are you measuring the "real life" NM? A few things to remember:

• TVFool's NM assumes an isotropic antenna (a theoretical antenna that is omnidirectional in 3 dimensions). A more directional antenna will have a higher gain and and thus result in a better "real life" NM.
• It also likely assumes a somewhat typical first stage amp (my guess is one with about 5dB NM). A better amp (with a lower NM) will give better results.
• When dealing with 1 and 2 edge diffraction, it will be making assumptions about the foliage on the terrain blocking LOS. A rocky cliff will result in you receiving more signal than hill with 100 foot ceder trees as the trees effectively increase the height of the hill by 100 feet. I would assume TVFool assumes something in between.

[holl_ands]

Andy.S.Lee explains TVFool calculations here:
http://www.tvfool.com/index.php?opti...d=57&Itemid=89

"If you take the initial NM value for a given channel, add your antenna gain,
subtract all the other system losses, and still end up with a value above 0,
then you should be able to detect that channel."

Note that "should be able to detect that channel" actually refers to a statistical prediction of coverage called F(50, 90) with field strength curves derived for 50% of locations and 90% of the time
from curves which are also found in Section 73.699 of FCC rules, as described in FCC OET-69. Most people would be very unhappy the other 10% of the "time". He recommends a NM "pad" of 5-10 dB to ensure higher, esp. long term reliability (I recommend 10-20 dB to include Clutter Loss, Man Made Noise and other factors):
http://transition.fcc.gov/Bureaus/En...et69/oet69.pdf

System Loss (aka System Noise Figure) spread sheet calculators found in Post#1:
http://www.digitalhome.ca/forum/showthread.php?t=42426
I adapted the calculations to compare three popular Preamps to NO Preamp:
http://photos.imageevent.com/holl_an...0holl_ands.xls

Or ADD Balun Loss (plus Antenna to Preamp Coax Loss if any) to Chart value:
http://www.digitalhome.ca/forum/showthread.php?p=888368
Chart assumes a Tuner Noise Figure = 6 dB. Only the best Tuners are this
good...older specs I've seen are in 6 to 10 (max) dB range. NAB/MSTV
sponsored tests by MSW on CECB Coupon boxes found NF = 5 dB (+/- 1 dB):
http://www.nabfastroad.org/NABSTVDig...lConverter.asp

He states that you should convert dBi Antenna Gain values to dBd (= dBi - 2.15 dB),
hence he actually assumes the GAIN of a Dipole Antenna (perfectly pointed toward
each transmitter when calculated).

================================================
TVFool as well as several other Propagation Prediction Programs (e.g. Radio Mobile) use the Public Domain code available for the Longley-Rice Irregular Terrain Model (ITM), which does NOT include any "Clutter Loss" values (additional scattering due to irregularities along the propagation path):
http://en.wikipedia.org/wiki/Longley%E2%80%93Rice_model
http://ntiacsd.ntia.doc.gov/msam/
http://www.its.bldrdoc.gov/resources...e/itm/itm.aspx

FCC has considering modifying their official model (used to predict station-to-station interference protection range) but there is a lack of public domain INFORMATION regarding how much Clutter
Loss along each and every propagation path (heavily depends on building types and density, small deviations in terrain smaller than SRTM measurement accuracy, seasonal foliage density, et al.). So FOR THEIR PURPOSES, FCC did NOT modify their downloadable propagation model, but did issue OET-72 with broad-brush recommendations for likely Clutter Loss corrections (see Table 3 on pg8-9):
http://transition.fcc.gov/Bureaus/En...et72/oet72.pdf
http://hraunfoss.fcc.gov/edocs_publi...C-00-185A1.pdf

But in Jun2008 submission to FCC re changing ILLR Model, MSW concluded that ON THE AVERAGE, there was NO NEED to apply ANY Clutter Loss corrections:
http://apps.fcc.gov/ecfs/document/view?id=6517882072 [See para 74]
[So, ON THE AVERAGE, ILLR underestimation of Clutter Loss in Urban areas results in an OVER-prediction of coverage area that is counterbalanced by the UNDER-prediction of coverage area for Rural areas.....so BOTH ARE IN ERROR!!!]

Since TVFool doesn't have any operator entries to select Clutter Loss conditions, clearly it does NOT include ANY Clutter Loss correction (as is found in most of the commercial Propagation Prediction Programs employing Clutter Loss map databases based on proprietary radar measurements). If you further investigate this issue, you might also find recommendations for SMALL Clutter Loss corrections
in the Hi-VHF Band....but the biggest correction needed for VHF (esp Lo-VHF) is the Man Made Noise levels are MUCH higher than the ASSUMED Thermal Noise levels stipulated in FCC OET-69...which is why VHF ERP levels were increased:
http://hraunfoss.fcc.gov/edocs_publi...C-05-199A3.pdf [See pg9-10]

TVFool and other ILLR programs also don't have the resolution to calculate the ADDITIONAL Loss due to being located behind a 50-ft hill (my location for 2 stations).
Nor the possibility of picking up a REFLECTION from a nearby mountain or building....
And Tropospheric Propagation is NOT included in TVFool or other ILLR program calculations...so don't be surprised if some signals come & go as weather changes....

[envirogeek]

Roger1818,

Either a poor choice of words and/or an incomplete expression of my intended point on my part.

I'm not re-evaluating or recalculating the NM.

What I was trying to get across was that if someone really cared about getting a channel with a reported NM of -1.7, TV Fool gives an indication that putting up an antenna is worth the effort.

In the "real world" of my particular installation i receive a channel with an even lower reported NM of -24.5 more consistently because of my personal choice of where to aim for channels that are higher priority to me.

I ran the spreadsheet calculations for my fringe location before putting up the antenna at the original height. Just for interest sake I might run them again at the new height to see the result.

UPDATE: I found my spreadsheet from August 2011, and updated it with current TV Fool numbers. The current NM values in TV Fool are lower across the board now than what I used then. Based on the current numbers 4 of the 7 channels I am receiving end up with calculated System Noise Figures in negative values.

August 2011 TV Fool values give me calculated NMs of -1.5 to 15 while today I get from -21.5 to 9.4.