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Old 2009-03-10, 04:05 PM   #1
balm
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Default TVFool Canadian Discussion

I punched in my exact coordinates in Montreal, post-transition, and selected digital channels only this time in Fool - and CBOt # 25, now appears, whereas before with digital and analog channels selected it didn't appear (only its analog #4),

and CBOt # 25 is Nm = -16, Power= -106.8, are these discrepencies errors or is there a reason for this,

also what is it about my antenna that allows me to get this one (albeit sometimes)...
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Old 2009-03-10, 04:21 PM   #2
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and CBOt # 25 is Nm = -16, Power= -106.8, are these discrepencies errors or is there a reason for this,
this belongs in the Ottawa status thread, or more properly we should start up a TVFool thread here like they have at AVSForum (if we could convince TVFool developer Andy Lee to join us here.)

TVFool post-transition reports now include the FCC's view of the Industry Canada Canadian post transition plan. In that plan, CBOT-DT gets to raise its power to 480 kW. You will also notice some other stations have improbably high ERPs, like 845kW or 1MW for some stations that have one half to one tenth that power on the same frequency currently on analog.

Quote:
whereas before with digital and analog channels selected it didn't appear (only its analog #4),
Because TVFool imposes a limit on how many stations it will display in a report, so in the combined report, it fell off the end.

By the way, you could figure out stuff like this for yourself -- just click on the CBOT-DT line in the TVFool signal locator jpeg result, and it will build a new screen with a profile of the signal strength between you and the trasnmitter site, as well as a few key data facts, like the originating stations ERP in your direction. You can also go to the FCC site TVQuery to see what data TVFool is using.

In any case, a -16dB NM station is going to be only an occassional tropo-enhanced visitor to your TV screen.

TVl
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Old 2009-03-10, 05:10 PM   #3
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tvlurker:

thanks, makes sense...

the main reason I'm posting this here is because I wanted mclapp's designs and help to make my antenna wider beam...but I see your point also....now you will get me in trouble(LOL)

BTW who could convince Andy Lee, and how do we reach him, at the Folol site...

I noticed that just by raising the height selection to 35 ft from 25 ft, CBFT-3 went from NM=-14.6 to -0.7, only this channel made such a difference

thanks for the help
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Old 2009-03-10, 05:18 PM   #4
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BTW who could convince Andy Lee, and how do we reach him,
There is a contact us link at the TVFool site. You probably want the 'feedback' link.
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Old 2009-03-11, 12:13 AM   #5
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Originally Posted by tvlurker
we should start up a TVFool thread here like they have at AVSForum (if we could convince TVFool developer Andy Lee to join us here.)
Agreed - I've split this off into its own thread here for Canadians to discuss the results they get from TVFool. Andy is more than welcome to join here too.

My hope is that Industry Canada data will find its way into TVFool sooner or later. This has been proposed in the past involving my IC data pump:

http://www.user.dccnet.com/jonleblan...a_TV_Stations/
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Old 2009-03-11, 12:43 AM   #6
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Agreed - I've split this off into its own thread here for Canadians to discuss the results they get from TVFool. Andy is more than welcome to join here too.
Yeah, and maybe another thread for weird TVFool results because of experimental repeater stations ( and others like circular polarization transmission tests in cities).
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Old 2009-03-11, 07:16 AM   #7
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My hope is that Industry Canada data will find its way into TVFool sooner or later. This has been proposed in the past involving my IC data pump:
OK - here is my summary so far of the isssues with the FCC's copy of IC data:

1. TVFool uses (I think) RCAMSL for antenna elevation, which is not always filled in for Canadian data

2. There is a lot of stale Canadian data for analog stations (eg. CHOY-TV 4 St Jerome, which AFAIK has not been around since the 80s)

3. Canadian directional stations do not have links to antenna pattern data, even though that data was included in the FCC/IC LOU, so TVFool assumes omnidirectionality, which will overstate transmitted power in some directions.

4. TVFool does not differentiate between Canadian post-transition digital (GRANTS) and analog stations, so flash cut stations have both entries listed. This is sometimes handy to directly compare the two stations.

5. The LOU contained a snapshot from July 2008, so it includes CRTC applications that were later denied (eg. HDTV), or missed later changes (SunTV Ottawa on 20)

6. Some Canadian stations are missing or wrong

Some problems are with the Canadian post-transtion plan, which TVFool can't be expected to fix:

7. A lot of Canadian post-transition allocations have improbably high ERPs, higher than the current ERPs on the same channel. Does anyone really thnik that 55kW analog CITS will build an 845 kW station at Herberts Corners

8. A lot of Canadian post-transtion allocations seem to have pulled EHAATS out of a hat. For example, the Herberts Corners tower in OTtawa is about 200m tall, but the plan puts all the stations at 300m (a nominal value). For Camp Fortune, one UHF station is placed at the top of the tower along with VHF channel 9.

For some American stations:
1. The CP and Licensed status of some stations is not always up to date. (eg, we don't know if WCFE is operating at 55kW or 100 kW, WCWF doesn't appear at all.)
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Old 2009-03-11, 11:35 AM   #8
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Originally Posted by tvlurker View Post

2. There is a lot of stale Canadian data for analog stations (eg. CHOY-TV 4 St Jerome, which AFAIK has not been around since the 80s)

6. Some Canadian stations are missing or wrong

For my 2 cents:

1. Some digital real channel #'s are not consistent with other published accounts for that channel #(e.g. CBMT Real shows #36, vs #21)

2. Would be useful to have a column showing the temp. transitional digital channel #'s (e.g. CFJP # 35 is using # 42)

3. Would be very usefull to have column showing the Network for all channels, especially Canadian ones (e.g. CFTM # 10 - Network "TVA")

4. CKMI (Global) # 46 Analog seems to be missing

5. Would be useful to have the Coordinates Degrees to Decimal converter embedded within the Fool site

6. Could have the ERP, elevation, data also in the columns
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Old 2009-03-11, 02:13 PM   #9
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Originally Posted by balm
3. Would be very usefull to have column showing the Network for all channels, especially Canadian ones (e.g. CFTM # 10 - Network "TVA")
Two comments about that:
  1. the IC database often does not have the "network" database field populated (network affiliation is more a CRTC matter than an IC one)
  2. given the musical chairs game of station ownership that has taken place in Canadian broadcasting over the past few years it is really difficult to consistently maintain proper network affiliation data
Both of those points means that someone would have to go through the IC database and add all that data manually, which would be very time consuming.
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Old 2009-03-11, 03:34 PM   #10
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Stampeder:

too bad their was no program which could automatically fetch the changing data - Oh in a perfect world!
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Old 2009-03-11, 04:14 PM   #11
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too bad their was no program which could automatically fetch the changing data - Oh in a perfect world!
There is, but TVFool fetches data from the FCC database, not the IC database.
And the FCC databse often has problems even with American data, let alone Canadian border station data.
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Old 2009-03-14, 11:18 AM   #12
balm
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Default tvfool technical questions..

I read up TVFool's own explanations, but

can someone explain:

1. how TVFool derives the NM figures, so that might further explain what exactly NM means...

2. how TVFool derives the Pwr figures, what the relationship is to ERP, and why it is expressed as negative values (higher power is a smaller negative value)...


thank you
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Old 2009-03-18, 05:55 PM   #13
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Default tvfool Noise Margin Figures For Laurentians

Does anyone know if tvfool is taking elevation above sea level into account on radar plots for antenna locations in the Laurentians, west of St. Sauveur by about 30 km?

I checked tvfool for a location west of Laurel near Lost River and got really poor noise margin numbers when plugging in an antenna height of 25 feet (although the elevation above sea level is over 250 meters). The location is 123 mi from Mt Mansfield and 86 mi from Lyon Mountain. The NM figures and my Tivax signal readings are shown below:

(Actual)-- (Station)-- (NM)--(Tivax Reading)
Ch 13.1 (WVNY) (-25.4) (15 to 27)
Ch 14.1 (WPTZ) (-14.3) (15 to 27)
Ch 19.1 (CBFT) (****) (15 to 27)
Ch 20.1 (CBMT) (****) (0)
Ch 27.1 (CIVM) (****) (0)
Ch 33.1 (WNPI) (-29.9) (15 to 27)
Ch 38.1 (WCFE) (-18.4) (15)
Ch 32.1 (WETK) (-31.5) (15 to 27)
Ch 42.1 (CFJP) (-21.5) (0)
Ch 43.1 (WFFF) (-35.6) (15 to 27)
Ch 53.1 (WCAX) (-21.3) (0)

*** NM numbers for Montreal stations, due to low power and temporary locations while the Mount Royal issues are being resolved are probably inaccurate in tvfool and are not shown.

Last weekend I took up a converter box (Tivax STB-T8) and attached it to a UHF 4 bay bowtie (looks like a CM 4221 and Delhi pre-amp) on a 45’ tower. With really poor noise margins predicted by tvfool I didn’t expect any signals –well I didn’t lock on anything but on a manual search, six of the channels showed activity with the signal meter jumping between 15 and up to 27, indicating a signal was present and some packets were being received. The same channels (except WNPI and WFFF) were comfortably viewable in analog, with some sparkles, before the shut down. I checked the antenna and it is pointing 180 deg (magnetic) well away from Mt Mansfield at 153 deg magnetic. Unfortunately, the rotor is stuck at 180 deg knocking out further testing.

I read through the posts by Smog, in Prevost. He is 120 miles from Mt Mansfield and receiving US stations well except for 3.1, at an elevation of 263meters. Has anyone else had experience receiving DTV in the Laurentian mountains west of St Sauveur? Are tvfool predictions for the Laurentians accurate and, do they take elevation above sea level into account?

sparky mtl
SBGH Gen 1; old 19” Sony; Tvax STB-T8 converter box
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Old 2009-03-21, 02:34 AM   #14
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Quote:
Originally Posted by balm View Post
I read up TVFool's own explanations, but can someone explain:

1. how TVFool derives the NM figures, so that might further explain what exactly NM means...

2. how TVFool derives the Pwr figures, what the relationship is to ERP, and why it is expressed as negative values (higher power is a smaller negative value)...

thank you
TVFool uses the Longley-Rice Irregular Terrain Model (ITM) developed by the U.S. Govt,
which is widely embedded into a variety of free and commercial VHF/UHF Propagation
Prediction Programs (PPP).
ITM uses physical calculations for line-of-sight, diffraction, refraction and troposcatter
path loss, based on empirically derived statistical models, which in turn are derived
from a very large database of many decades of actual on-air signal level measurements.

On-line TVFool uses hi-rez SRTM (Shuttle Radar Topography Mission) terrain database
to calculate very detailed signal level estimates along the path to your location.

The torrent downloadable signal level maps are medium resolution, whereas a very
low resolution is used for TVFool's on-line signal level maps. To reduce calculations,
signal level maps use fairly large (e.g. 1km x 1 km or larger) "calculation blocks".

Transmit ERP (kW) is the amount of Effective Radiated Power towards the azimuth
with the HIGHEST transmit antenna gain. When available, TVFool uses the reported
antenna pattern to calculate the ERP towards YOUR location....otherwise it assumes
an omni-directional pattern.

The Receive Pwr(dBm) level is a statistically derived estimate of the signal level delivered
by a 0 dB gain antenna....hence it is a large negative number, since signal power levels
are on the order of femtowatts (dBf) rather than milliwatts (dBm):
http://en.wikipedia.org/wiki/Decibel
dBm = 10*log(power/1mW) so 0.001 mW = -30 dBm.

ATSC requires more than about 15 dB SNR and Thermal Noise level is about -106 dBm.
Hence the PERFECT, THEORETICAL sensitivity is about -91 dBm. The actual sensitivity
is found by SUBTRACTING the Antenna Gain (Ga) and ADDING the overall System
Noise Factor (NFs). Thus, for a 10 dB Gain antenna and 3 dB NFs with Preamp,
actual sensitivity is -98 dBm. [Compare to -83 dBm CECB spec without Preamp.]

NM (Noise Margin) after ADDING Antenna Gain and SUBTRACTING System NF,
is an estimate of the amount of EXTRA signal level over and above the sensitivity level.
For more reliable reception, NM should be in the range of 10+ dB.
[I also suspect that TVFool did not include Land Use Clutter Loss per FCC OET-72.]

Reception of signals with negative NM are possible if your location is "better than most"
and/or extraordinary conditions are in effect, such as tropo-ducts over and near water.

However, bear in mind that ITM is a STATISTICAL model guesstimating the signal
level that will provide "acceptable" reception 90% of the time for 50% of user
locations (in "similar" propagation conditions...I did say it was a statistical model).

Andy has additional explanations in the TVFool thread on AVS Forum.
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Old 2009-03-21, 03:33 AM   #15
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However, bear in mind that ITM is a STATISTICAL model guesstimating the signal
level that will provide "acceptable" reception 90% of the time for 50% of user
locations (in "similar" propagation conditions...I did say it was a statistical model).
Heh, so in general, theyre only estimating it to be correct 45% of the time overall ?
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