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

[donj]

Cool, thanks. This gives me an idea of what I can get come Sept 1.

FYI, the effective erp for my location is 0.613 kW and I can get Global pretty stable with a folded dipole in the attic with a preamp.

[charettepa]

nice
thats about 7x the erp i get

[stampeder]

Originally Posted by donj

How do you find out the erp at your location?

The answer is that you cannot. The term "ERP" means Effective Radiated Power and is an engineering calculation that rates the power only at the transmitting antenna. So, I think we all know what you are trying to say but ERP is not a term you would use to describe the field strength at your own reception antenna.

For consumers looking at their TVFool reports one of the most important factors is the Noise Margin (NM), amongst other considerations. Post your TVFool Report link and our experienced members can give better advice.

If you really, really want to know in very detailed discussions of how the TVFool site reports work see the following thread:

TVFool Canadian Discussion

[tvlurker]

Both stampeder and charrettepa are right. In effect, the ERP is at the transmitter site, but it does vary by direction.

Effective Radiated Power is a way of saying: for a receiver in a given direction, how much power would the antenna have to emit in every direction for the receiver to receive the field strength it is in fact receiving. In effect, you can think of it as "how much power is the antenna throwing in my direction".

So stampeder is right in the sense the receiver's distance from the transmitter is irrelevant. And charrettepa correctly noticed that TVFool reports a different effective power in every direction away from a directional transmitting antenna. However, all locations at the same azimuth report the same effective power .

[charettepa]

thanks for clarifying
that makes sense to me

my real question now is to global
why do they throw over 400w in most directions and only 81 in my direction
its a dense population

unless they "TVFOOL" are taking terrain into consideration
then it would make sense as i am in a valley (bottom of hill in orleans, by the river)
global reffered to it as a "null"

[charettepa]

ok just did a little test

TVFOOL is definatly taking terain into consideration when reporting the effective ERP (adjusted according to your location)

as i just checked using the in-laws postal code
from their house they use the same azimuth to aim (point in exact same direction on compas)
but are ~15km furter away but in same dirrection as myself in relation to the tower
yet have 4x the reported effective ERP
which of course gives them better reported dbm/nm values

[tvlurker]

I can't reproduce your issue. When I look at the effective power in the power overlay feature of the online TV Map feature of TVFool, it does not vary for the same azimuth.

With respect to the low power level in the direction of Orleans, bear in mind that Global is using an antenna designed to protect channel 6 in Montreal. That's why it cannot send much power to the east.

Even post transition, channel 6 in Montreal remains an allotment that needs to be protected (but not as much, as up to 5% interference by population is permitted for vacant allotments.)

[charettepa]

it reports 0.081 for me
and 0.12 for my mother in-law
keep in mind
only a small portion of orleans is in a valley
you are probably thinking of the "new" orleans which is top of the hill
i am "old" orleans bottom of the hill
in fact if you look at my tvfool report which is in my set homepage
you can see the map it draws when you select global
you can actually see the dip in the terrain
and the section that is in that valley
has much less power

[roger1818]

I borrowed that Spartan 3 pre-amp and did some experimenting yesterday and I must say things are about as clear as mud right now.

I saw that Global was down late morning/early afternoon so I did the swap to see if it would help. It didn't. Frustrated I just left things alone and continued to try it throughout the day. It still wasn't coming in in the evening and I thought that maybe something changed and I need to do a re-scan, which I did and sure enough it started to come in again. So now I am not sure what problems are on the transmitter side and what are problems on my end. After the re-scan I did have it fail once but trying again immediately it was able to get a lock. I will probably keep the pre-amp installed for a while and see how well it performs, but at this point I am not holding my breath.

Just so everyone knows, I am using an HVR-950Q with MythTV for all my tests.

[charettepa]

they did a change last week on wednesday i think
maybe thursday
it was a change to PSIP if i understood correctly
i too had to rescan for it to work
it has worked since
in fact signal has been better since then
very little pixelation in most cases none

[OTAJuncqui]

If you're looking for a "clearer picture" of signal availabity download TVFool map overlays for google earth .
I doubt they have updated global info but you can use it as a benchmark

[Fota]

Originally Posted by OTAJuncqui

If you're looking for a "clearer picture" of signal availabity download TVFool map overlays for google earth .
I doubt they have updated global info but you can use it as a benchmark

RabbitEars.info has current info... For fun, here's a comparison of current Global TV and CBC. What's not shown here is that on top of the weak broadcast signal, Global TV's VHF-low cannot traverse/penetrate anything.
So I'm in Ottawa per se and can't get Global TV because it just can't penetrate my apartment building at all (yet I get all UHF digital broadcasts from Camp Fortune perfectly fine).
Images from rabbitears.info (+ google) composited in GIMP.

[Trip]

To add to the ERP question, let me offer a link to a feature on RabbitEars that may help a little bit. (Does not work with IE versions older than 9, may have other incompatibilities I am unaware of but works in Firefox/Chrome/etc for me.)

http://www.rabbitears.info/oddsanden...tion=0&erp=3.3

That is the CIII-TV-6 antenna pattern. If you hover your mouse over the little white dots, the ERP is displayed for that direction coming out of the antenna.

Not sure if it will help, but maybe.

- Trip

[Trip]

Originally Posted by Fota

RabbitEars.info has current info... For fun, here's a comparison of current Global TV and CBC. What's not shown here is that on top of the weak broadcast signal, Global TV's VHF-low cannot traverse/penetrate anything.

One comment I'd like to make about my coverage maps is that I actually adjust the maps for VHF downward in terms of coverage to attempt to account for the poor characteristics of VHF (It's adjusted 5 dB for high-VHF, and 13 dB for low-VHF) but since noise floors are not consistent everywhere, a station like CIII-TV-6 might be reduced significantly more than a station like KXLF/KTVM in Butte MT.

(If you're wondering where the numbers 5 and 13 came from, the "normal" numbers for the bands are UHF-41dBu, high-V-36dBu, low-V-28dBu. Do some subtraction and my laziness will come into focus. )

- Trip

[old sparks]

Trip;

Thanks for the link! It really illustrates the directional nature of the CIII RF6antenna and why I can receive it with the equivalent of a 'wet noodle', whilst those who live in the east end are forced to take extreme measures!

CIII needs to migrate to a UHF channel if they really want to serve the City of Ottawa as well as Gatineau to their respective borders. This should be a minimum mandatory requirement...