Several members have tried UVSJ splitters to help attenuate strong/close by VHF signals, including myself. I eventually found that a channel specific trap (VHF 11) seemed to work best for increasing signal strength on more distant/weaker UHF channels. However, I recently tried using 3 (three) UVSJ splitters consecutively, and it was comparable to the channel specific VHF trap. So for those looking to filter out VHF channels, multiple UVSJ splitters might be something to consider instead of making or building a channel specific VHF trap.

That can certainly work provided you only want to receive UHF station. if you have any VHF stations other than the problem one, they will also get lost in the cascaded UVSJs.

Putting a notch filter on VHF 11 is ok for now but I read that CH plans to move their ATSC signal to the main transmitter after the transition. Will it have the same high signal strength as it currently has now, or will it be transmitting at a much lower power, making this less of an issue?

That's an understandable concern but two of the many benefits of ATSC DTV are its almost complete elimination of ACI (Adjacent Channel Interference) and CCI (Co-Channel Interference) so it is expected that combined with CHCH's much lower post-transition ERP you won't have the problems you're now seeing. A fix for the present analogue troubles with 11 is a necessity for some people today, but not a permanent one.

Is there a chart/thread somewhere, or is it even known what the post-transition signal strength of the Canadian DTV stations is going to be?

I am confused as to why the Buffalo major networks DTV stations are all broadcasting at 360kW, 480kW, 790kW, 1000kW and the Canadian ones are all <50kW. Maybe it is because their primary transmitters that are capable of the high powers are in use for the analog signal and the digital ones are just temporary...

Is there a chart/thread somewhere, or is it even known what the post-transition signal strength of the Canadian DTV stations is going to be?

Here is the preliminary DTV Post-Transition Allotment Plan (http://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/DTV_PLAN_Dec08-e.pdf/$file/DTV_PLAN_Dec08-e.pdf) from Industry Canada. The signal strengths in this document can be considered maximums and in reality they will likely be significantly weaker. We won't know the actual signal strengths until the stations start applying for their Post Transitional licenses.

I am confused as to why the Buffalo major networks DTV stations are all broadcasting at 360kW, 480kW, 790kW, 1000kW and the Canadian ones are all <50kW. Maybe it is because their primary transmitters that are capable of the high powers are in use for the analog signal and the digital ones are just temporary...

The fact that the Canadian transmitters are transitional is one factor. Even then, the Canadian transmitters seem to be weaker than the American transmitters were during their transition. Post transition the contours will be required to match the analog contours, though some old stations have contours grandfathered that are larger than permitted today and thus will be reduced.

Carried from the East of Oshawa Thread:

I have a question for the members. Channel 3 Syracuse was bouncing in and out tonight from 5 bars, drop to 0, back up to 5, back to 0, etc. Is this an overload problem? I shoot through 32,38 and 11 to hit Syracuse. I really should have entered in a TV fool report before buying the house. I'll know better for next time.

Here is my TV fool report. http://www.tvfool.com/?option=com_wr...b7c80762ef5019

I have priced an attenuator from Tin Lee which would attenuate 32 to 38 but pass 35. It wasn't as bad as I thought it would be and I don't mind paying, I am saving money by not having cable.

It was suggested as a reply in that forum from another member to try a stub filter but would that work to attenuate multiple channels?

I shoot through 32, 38 and 11 to hit SyracuseI understand your possible problem - if you're trying to pick up U.S. UHF channels to the South - you will be pointing your antenna almost right at those powerful nearby transmitters at the same time.

I looked at the TV Fool report you provided, based on the internet link in your earlier post.

Your TV Fool location says your location is Glenburnie - just north of Kingston. Based on the TV Fool, the transmitters for 32, 38 and 11 are almost exactly in line with the direction, from your location, to Syracuse and Watertown transmitters. Ch 32 and 38 transmitters show only 2.4 miles away from you (!) You're very close to the transmitting antenna for 32 and 38. Those signals must be very powerful at your location.

If 32 and 38 are causing overloading or interference problems, receiving other channels, I read somewhere in the forum that one member nulled out a channel with the use of a properly designed "stub tuner".

Stub Tuner = a piece of coax cable, cut to the right length to NULL the channel in question, and "Tee'd" off your downlead. Probably near the antenna, before any pre-amplifier is best location.

Theory: Signal of channel you wanna kill, or attenuate sharply, goes down the piece of "Stub Tuner" coax, reflects off the Open circuit at the end of the STUB piece of coax, travels back down the Stub again and reaches the "T" point exactly 180 degrees out of phase with the original signal.

Result: It cancels out (most of ... or alot of) the signal of that channel.

It acts like a notch filter. (band reject filter. opposite of band pass filter)

Not sure if it's possible or practical at the UHF frequencies of ch 32 and 38 ... wavelengths are alot shorter at those UHF frequencies ... but some sort of "stub tuner" might be worth investigating.

If I remember correctly ... one member in Ottawa area nulled out powerful VHF 4 this way ... a powerful CBC signal that was causing RF interference on a higher channel he was trying to improve reception on. The higher channel was on a "harmonic" of VHF 4 ... hence suseptible to interference from ch 4.

We studied this stuff way back in University EE program - in a Transmission course. Interesting - and sometimes practical to do this.

You only need T-connectors, coax, cutters, and some formulas and some knowledge and some calculations.

Maybe look into that. Maybe some other members can provide some advice too.

That's an understandable concern but two of the many benefits of ATSC DTV are its almost complete elimination of ACI (Adjacent Channel Interference) and CCI (Co-Channel Interference) so it is expected that combined with CHCH's much lower post-transition ERP you won't have the problems you're now seeing. A fix for the present analogue troubles with 11 is a necessity for some people today, but not a permanent one.
I understand this, but what if you live right beside a tower that has a half decent digital ERP coming off it? Will this very close-by digital signal not have an impact? My problem with CHCH is not co-channel or adjacent-channel interference, I just live right beside it and it blocks out my weaker stations that are not co- or adjacent-channel.

what if you live right beside a tower that has a half decent digital ERP coming off it?Look to the U.S. for real world examples. In Seattle the towers of KOMO (channel 38) and KIRO (channel 39) are literally right beside each other on adjacent lots. These are both Class A stations pumping out enormous power. So, what do folks living almost underneath those towers have to say about one channel affecting the other? Nothing. There is no problem. :)

In this video (http://www.digitalhome.ca/forum/showpost.php?p=1055871&postcount=78) you can see the houses and apartment blocks right below the KOMO and KIRO towers, and at 3:18 you can see both the KOMO and KIRO towers side by side.

In the post-transition period I expect that people in the nearby vicinity of CHCH will see their channel 11 interference problems go away when the analogue transmitter is shut down.

Look to the U.S. for real world examples. In Seattle the towers of KOMO (channel 38) and KIRO (channel 39) are literally right beside each other on adjacent lots. These are both Class A stations pumping out enormous power. So, what do folks living almost underneath those towers have to say about one channel affecting the other? Nothing. There is no problem. :)

The problem with your example is the two towers are close to each other. The concern is when they are far apart since the dynamic range between the two signals becomes very large. This can cause problems even if the stations aren't on adjacent or alternate channels.

In this video (http://www.digitalhome.ca/forum/showpost.php?p=1055871&postcount=78) you can see the houses and apartment blocks right below the KOMO and KIRO towers, and at 3:18 you can see both the KOMO and KIRO towers side by side.

But are those houses able to receive signals from Vancouver or Victoria?

In the post-transition period I expect that people in the nearby vicinity of CHCH will see their channel 11 interference problems go away when the analogue transmitter is shut down.

I agree that things will be much improved post transition, but I can't guarantee they will "go away" completely for everyone.

recently I was in search for a was to control a very strong signal from local CFPL here in London Ontario. I am using a preamp to assist in some fringe signals and am feeding three televisions.
Recently I added a VHF antenna to my setup and this caused havoc whenever I pointed towards the Cleveland market as this CFPL tower is almost in the way.
I called Tin Lee and with his experience and others here on this very forum I had a multiple bandstop built for my location. The CR7X I chose was an outdoor unit that custom attenuates channel 10 (30 dB) and also on his recommendation extra attenuation for FM. I chose frequencies 93-99 MHz to attenuate (55 dB).
This custom made product has worked wonders. I cannot get to the roof to put it in place at the antenna just before the preamp so for the time being I installed it just after the preamp power source and just before my three way splitter.
I think it works pretty good there for the time being until the snow leaves my roof.
I'm pretty sure people in different locations though out could benefit on something like this if you have a strong station in your way.
For example if you live in north of Baden, On you would have channel 13 CKCO 13 in your way..... you get the idea.
I called on Friday of this past week and received my custom made bandstop on Monday afternoon delivered by UPS.
It came with a Transmission log and showed the scope tests performed.
It cost around the price of a decent pre amp.
I wanted to pass this along so others whom might suspect they are in the same boat might want to try.

Mark

Wouldn't a notch filter like this also attenuate adjacent channels 9,11 to some extent too? I heard that notch filters can't quite be built to the exact tolerances of only 6 mhz. (channel size)

Okay ramble time..

I really need to take out a local ch 16 (CHWI-TV) by over 40dB here. Digitals on 15(WEWS) and 17(WKYC) are severely weakened to the point where they are too volatile and not watchable many times, especially with changes in ch 16 local programming like flashy commercials or scene changes. The offending CHWI is 9 miles away at ~500kW erp.

16 also "bleeds" all over the dial, especially once I rotate the antenna to face their tower to the northeast. This shows up as inverted b/w silhouettes, black and white blobs etc with no audio. This happens to be the most visible in NTSC channels 19,20 and 24. These channels are vacant in this area and should only be analogue snow. Is there any cheap way to only take out 16 but not affect 15,17?

Other observations: on a rare very strong tropo day months ago another American digital on rf16 reduced local ch16 station to black and white snow with the audio carrier barely there and these bleeding issues pretty much disappeared totally for a short time.

I want to be sure this local station is the problem, so I don't have to spend a wad of cash for nothing. I have two separate antennas mounted in different locations on my property that would need this attenuation for 16. Hoping one day soon it will go off the air for maintenance or something and I can then check all the channels i'm having problems with.

People.. a coax notch filter takes maybe an hour tops to prepare. Make it overly long, and then just sit there snipping 1/8" at a time from it and watch what happens to your reception.

Total cost, maybe $3 and an hour of you time. That's probably less time than you're spending digging through the postings here wondering if it would help or not !!! ;)

So, try it. If it doesn't work out, no biggie. But it probably will help in quite a few cases.

Cheers

People.. a coax notch filter takes maybe an hour tops to prepare. Make it overly long, and then just sit there snipping 1/8" at a time from it and watch what happens to your reception.

Indeed, that would be a fun experiment

@Phil81
there is a tad bit of attenuation on channel nine and eleven according to the scope results. Looks like around 3 db. In your case I know that channel 16 is in Wheatley so I don't know how much off that is compared to pointing towards the Cleveland's. I suspect it is much like what I have.
You could chose the cheaper coax notch filter, or you could just PASS GO and go directly to a product as I have described. In the end it could be an expensive thing if does not work.
That's the fun thing to (my hobby). I am the kind of person that will mess around till I get it right. Then when I am done I say "What's next?"

here is the scope results for my trap:
http://www.digitalhome.ca/forum/picture.php?albumid=120&pictureid=2188

Thanks for the suggestions guys.
indeed the cheap approach first. I have a bunch of standard RG59 coax laying around I could try. Not sure this would solve the problem though. That station is so quirky that I get the same type of bleeding interference I described with a unamplified tiny uhf loop antenna indoors even. I took some pictures of this in December with that same cheap uhf loop antenna tuned to ch 20-0. Same result for multiple tv's old and new and also different antennas indoors and out.
Got to be something not quite right over there at their transmitter or something, not properly staying within proper channel boundary? Again this didn't ever happen before spring 2009.
WEWS was watchable down to 10-20% totally breakup free, but since about 1 year ago it's terrible with skipping and freezing depending on what programming CHWI-16 is displaying, even with more than adequate signal 60-80+%. WKYC is effected to a lesser extent though.

Same behavior on two other totally different atsc tuners (2008+ gen 6). Can't just be overload that is the culprit here.

Also noticed at the same time (and still to this day) that thin black lines occasionally flash quickly on and off that appear within the broadcast 24/7, but they do not appear on CHWI-16's repeater station serving Windsor on ch 60...There were also times on ch 16 where all colour was lost for brief periods here and there but that now happens much less often since late last year.

mlord, does a coax notch work on multiple channels? Can it be used to knock out two or three channels?

mlord, does a coax notch work on multiple channels? Can it be used to knock out two or three channels?
Each one is tuned to a specific channel so you would have to make two or three of them to knock out two or three channels.

Does tvfool or somewhere show fm stations and tv stations at the same time where you can see if maybe they are causing tv interference? I have a cm7777 with the fm trap on. I have two strong stations close to me on FM and one less than a mile from me. One is 94.1 and the other in 105.5 I got a Wade vip-306sr that i have not put up yet. I figured i would get interference from the fm stations and purchased a tin lee mast filter. He recommended i knock down 94.1 and 105.5 more so but also most of the fm band but hit those two stations harder. The Tin Lee & the Wade is not up yet. It will go up soon.

Today, i decided to try an Antennacraft 212 preamp as i needed to take my cm7777 down and do some minor repair and it has been working good. So i figured i would try the new 212 for a week or so and test it against the 7777. I am about as deep of fringe as you have seen(one close station(north) to me is 2 edge at 33 miles). I turned north to a station 73 miles away to test the preamp and i feel the 212 vs 7777 is very close. I do not want to say one is better than the other for me untill i test a week or so. I then turned to a station southwest of me about 55 miles. I shoot thru some trees going south close to my antennas. All this is on UHF with stacked 91xg's. A station that always comes in very good but not hardly as strong as the 73 mile station was not there. What was wrong?

I then flipped the 212 fm switch, as it is in the house and not at the antenna like the 7777. I presume i flipped it on or in and now here is my station at 6 bars. I could not believe how something could knock a signal clean off like that. On UHF and real ch 43. I have another station 45 miles away and it is pbs(less power also) and maybe 10 degrees off from ch 43 and it's real ch number is 47. It is suppose to be a better station i receive and it is one of my very worst. I have to wait late nights, if i get it and it was not in there with the 212 today and isn't with the 7777. I can normally always see one bar trying to come thru on that station.

I bought that Tin Lee filter for my VHF antenna but it seems to me something or fm can kill a uhf station also. How much loss is it adding the Tin Lee filter inline and is the only way to see if i am having fm interference and more than what the 212 or 7777 can trap out, is to test with the Tin Lee inline? Maybe test on a UHF antenna and then VHF also? I was wanting to try the new Kitztech amp out soon with .4 noise and an average db gain of 24. Later they are also thinking of adding switchable deep filtering for this amp as well.

What i saw today, i am afraid i can't use a preamp without filtering. If it can do that to uhf way up the band, just think what it can do to vhf stations up and down the vhf band. My vhf stations are on ch 5(2 stations), ch 8(about 3 of them), ch 10, ch 12. I like the idea of Research Communications filtering below ch 14 and above ch 51(usa band plan) but for that price, having to unhook it when not in use and it seems these get took out by lightning alot, scares of me of that amp also.

Does tvfool or somewhere show fm stations and tv stations at the same time where you can see if maybe they are causing tv interference?Andy at TVFool has links to his FMFool site but I don't believe he has an overlap tool unless I missed it. If you don't see one you could send him a request to see if he would want to build it into his site. If he could also show the second and third harmonics that would be fantastic, but I don't know if he has the resources to pull that off. ;) Otherwise you could print out your local TV and FM reports and eyeball them side-by-side to try to see where the signals might overlap.