QC - South Shore, Eastern Townships, Northern NY and VT - Page 49 - Canadian TV, Computing and Home Theatre Forums

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post #721 of 725 (permalink) Old 2016-08-10, 04:06 PM
Join Date: Dec 2008
Location: Crabtree, QC (Joliette) CM-3679, Pre-Amp Channel Master Modèle ??? (environ 20 ans)
Posts: 144
In the TVFool report you posted for DaveR450, you have to click on All Pending.
Then, you'll see CBFT-DT and CBMT-DT at the top of the report.
CBFT is the French CBC channel in Montreal and CBMT is the English CBC channel in Montreal.

That's why he can catch CBC so easily from Chambly
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post #722 of 725 (permalink) Old 2016-08-10, 06:16 PM
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Join Date: May 2010
Location: S.E. VA
Posts: 976
Thank you for the guidance, krusty79; I need all the help I can get. Being from Virginia, I do not have sufficient knowledge of your local conditions.

What is important is that CBFT-DT and CBMT-DT are much stronger than CIVM-DT and more likely to cause overload.


Aiming the two sections of the antenna in different directions doesn't always work, in spite of what the marketing departments say. The same signals from each panel can interfere with each other if they don't arrive at the combining point in phase (at the same instant). You didn't answer my previous question:

How does NBC do if you aim both panels at it?
I'm wondering if I could/should put an amplifier on the US pointing side only (and leave the Montreal pointing side well enough alone), or is that likely to mess things up even further...
If you did that, you would need a combiner that passes DC power to just one side for the preamp between the combiner and the antenna. But, a preamp would most likely cause overload.
Now that The Games have begun, I'm super happy that we can watch it on CBC, but I find that NBC (channel 5.1) is completely unreliable. The signal strength seems unchanged from before, varying between 40% and 45%, but it drops it constantly... Part of what's confusing me is that the signal's "Effective Power" (according to TVFool) should be 103.8 kW, while Vermont PBS is crystal clear from the same mountain with and "Effective Power" of 90 kW... Does anyone have any guidance for me on how strong a signal needs to be for it to be reliable?
The fact that the two panels are aimed in different directions might be a factor, as mentioned above.

The difference in ERP sent your way is quite small.

dB = 10log(P1/P2)
10 log 103.8/90 = 10log 1.15333 = 10 x 0.062 = 0.62 dB

Most UHF antennas of that design have a gain curve that starts out low at the CH 14 end, and rises with frequency, so the gain of your antenna is less for WPTZ on channel 14 than for WETK on channel 32.

The antenna pattern for the WETK transmitter is omni-directional, but the antenna pattern for the WPTZ transmitter is severely restricted in your direction to protect the reception of your local channels according to border agreements.

Although it looks like the two antennas are on the same tower, they are not. The slightly different location and the difference in frequency can make a difference in propagation.

I don't yet have your tvfool report, so I will have to use the numbers on my estimated report.

CBFT-DT has a signal power of -28.3 dBm = 20.7 dBmV
Max input of Channel Master 7778 = 34 dBmV
20.7 dBmV + 12 dBd ant gain = 32.7 dBmV; OK

CBFT -28.3 dBm + ant 12 dB + preamp 16 dB = -0.3 dBm; tuner overload if the antenna is aimed in that direction

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2016-08-10 at 08:44 PM.
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post #723 of 725 (permalink) Old 2016-08-12, 01:34 PM
Join Date: May 2011
Location: Vimont, Laval, Qc.
Posts: 1,112
I'm only a little more than 9 miles from the Montréal transmitters and I never had any overload issues with all the pre-amps I've used since 5 years. Here's my TV FOOL

And all those pre-amps were used with many CM4228 and some of my builds. True that I've always aimed those antennas at Mount Mansfield in Vermont (I'm north of Montréal).

Maybe it would be another story with a real clear LOS. Remember that TV Fool doesn't consider the buildings, trees and part of the terrain.

I also have a brand new CM7777 to be installed one day, far far away . . .
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post #724 of 725 (permalink) Old 2019-01-02, 03:39 PM
Join Date: May 2018
Posts: 2
Chateauguay, Quebec - help needed


I am using an OTA antenna with HDhomerun.

TV fools results using google maps coordinates : TV Fool

I have been using for a while a 4 bow tie antenna (dont know model or brand, but it looks like the picture on top of this forum) that was pointing to Mt Mansfield USA. I was getting almost all channels available (except ABC (WVNY)) but a couple were jumpy. But I had the most important french channels (French CBC, TVA, TQ) from Montreal very good even if i was pointing the USA.

In the past year, I did research to buy an upgrade antenna to get betters signals on channels (CBC + USA channels) but never pulled the trigger.

For christmas, my wife suprised me with an DB8E from antennas direct and i installed it yesterday.

Most channels are perfect, except I lost CBS (nice to have channels) and i have pixelations on TVA every 5-10 seconds (Deal Breaker). I use HDhomerun signal analysis to find the signal strength for TVA is strong 92-94%, but signal quality is wacky (changes every second between 55% to 100%) and symbol quality from 0 to 100% (but more often 0-10%).

While doing my investigation, i found out that DB8E is a UHF antenna and then TVA is VHF channels. Should I change antenna If I want TVA ?

Before posting my message, I just unplugged my hdhomerun and plug the signal from my antenna directly in a TV and all my problems disapeared. So I am abit confused. I wrote on HDhomerun forum if my hdhomerun can be the problem. https://forum.silicondust.com/forum/...?f=113&t=70562

But I still have a question. Should I return the DB8E if I want TVA ?

Thx for all help and sorry for long post.
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post #725 of 725 (permalink) Old 2019-03-25, 10:55 PM
Join Date: Jul 2007
Posts: 9
Problem tuning to one channel


I live in Brossard, south shore of Montreal where I can catch about local 9 channels with no issues since I have an antenna (old DB4) on the roof. It's pointed to Mt. Mansfield and my house is more or less between it and where most of my local channels are broadcasting (Mount Royal.) I have a pre-amp so I can catch US channels and still catch the local channel of the back of the antenna. It's been working fine for about 10 years now.

I have two "receivers" my TV which I seldom use to watch live tv and my Ubuntu server running Plex (MythTV before) with a Hauppauge HVR-2250 PCIe card.

Recently, just one channel CBFT-HD (SRC/19/2.1) has been having trouble tuning. It does not more often than it does. I checked a few times when the PCIe tuner was not able to tune to that channel and the TV had no trouble at all. Granted it's a recent LG TV and the tuner might be more sensible...

Tho, this channel can be tuned with no issues at >85% strength usually. Furthermore, I never have any issues with CBMT-HD (CBC/21/6.1) which is just two channels up in UHF and is broadcasted from the same tower and power.

So I'm getting a bit mad here. I don't understand what could be the culprit at all since all other channels can be tuned with the PCIe card and channel 19 can be tuned without issue on another receiver (the TV.)

Winter is almost over so I'll probably get on the roof to test removing the pre-amp and turning the antenna to point directly to where SRC/CBC transmit but I doubt that could be the issue... could it be as simple my PCIe card giving up? When previous PCI tuners (HDTV HD-5500) failed, the symptoms was signal strength getting lower across the board.. not just one channel.

Any idea(s)?


Last edited by 57; 2019-03-25 at 11:17 PM. Reason: Moved to Existing Thread.
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