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Old 2005-05-27, 12:57 PM   #1
stampeder
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Lightbulb OTA Mounts, Towers, Rigging Hardware

Okay, some of you might be stuck with HAVING to use the attic for your OTA antenna, but boy oh boy does it cost you signal strength and cause a bunch of other problems. If you are thinking about it or you have no other choice, at least be aware of the situation at hand. I saw a great post about antennas in attics on another forum that linked to a post on another forum from Bob Chase, a broadcast technician who regularly comments on OTA antennas and stuff over on AVSForum:
Quote:
Attics take a huge toll on the signal you get. The few that I have measured so far have been in the 20 dB range of attenuation. Those attics are made of standard asphalt shingles, over roofing felt, over plywood type construction. I have not been in an attic like yours.

Attics also cause reflections that the HDTV tuner has to equalize out and there is only so much equalization that is available. So that means there is less equalization available for the 'real world' multipath that is arriving over your house.

Some folks have good luck with the Channel Master CM7777 preamp. Inside the attic it is pretty hard to overload the front end of that particular amp. (Outside it can happen quite easily.) Given the right conditions, preamp will not overload but the output of the amp can overload the HDTV tuner . That is just one of the good reasons for using an attenuator at the receiver.
So, there's no substitute for an outdoor roof or mast mount if at all possible. And as far as good signal reception is concerned, remember what the fighter pilots say: "Altitude = Options".
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Old 2005-05-27, 10:49 PM   #2
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My antenna is not only up on the roof it's on a 10 foot mast above the roof peak. All this extra height adds to the gain too.
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Old 2005-05-31, 11:21 AM   #3
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Quote:
Originally Posted by stampeder
Okay, some of you might be stuck with HAVING to use the attic for your OTA antenna, but boy oh boy does it cost you signal strength and cause a bunch of other problems.


http://www.avsforum.com/avs-vb/showt...&&#post5399471

Summary:
So, there's no substitute for an outdoor roof or mast mount if at all possible. And as far as good signal reception is concerned, remember what the fighter pilots say: "Altitude = Options".
Thanks, that was quite interesting.

I've been thinking about getting a Channel Master 4228. The size of that antenna is just about the size of a south facing window on the second floor, out of which I can see the CN Tower.

Does anyone know what effect a double pane of glass would have on the signal strength of UHF frequencies? I've read that the gigahertz frequencies of satellite signals are blocked by glass, but what about the much lower frequencies of UHF?
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Old 2005-05-31, 12:23 PM   #4
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I believe glass has very little affect on VHF and UHF frequencies.

I should mention that the 4228 is hardly pretty!
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Old 2005-05-31, 12:28 PM   #5
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Quote:
Originally Posted by JohnnyG
I believe glass has very little affect on VHF and UHF frequencies.

I should mention that the 4228 is hardly pretty!
I was thinking that it would look like a good break-in deterrent! You could put a sign on that window saying "Protected by Channel Master. Electromagnetic hazard".

But seriously, unless you are incredibly lucky to already have the perfect azimuth to the broadcasters you want when you first mount it in the window, you would have an aiming problem so maybe another idea is in order. If all you want are the CN Tower stations then fine.

Last edited by stampeder; 2005-05-31 at 12:47 PM.
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Old 2005-06-01, 09:27 AM   #6
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Quote:
Originally Posted by JohnnyG
I believe glass has very little affect on VHF and UHF frequencies.
You're probably right about that. A friend of mine brought over a very small bowtie antenna, 8 to 10 inches long. It was probably smaller than just one of the eight antenna elements on the 4228. I pointed it out the window and managed to get most of the Grand Island Buffalo analog UHF transmitters, which are about 50 miles away. The channels were a bit fuzzy though.

All of the CN Tower analog UHF channels came in very clearly. In fact, the video was much better than the very same channels over cable, much less noise and sparkling around the edges. I was able to switch back and forth between the antenna and cable inputs and the comparison was very easy with very little time delay in viewing the two images.

I was very surprised at the very large difference in video quality, and this was only between OTA vs cable SDTV, not OTA HDTV compared to cable SDTV.

BTW, my friend tried that same bowtie antenna in his basement and had roughly the same results. The Grand Island channels were fuzzier, but he was still able to get something. So it seems UHF frequencies have pretty good penetration, even through brick and wood.

Quote:
Originally Posted by JohnnyG
I should mention that the 4228 is hardly pretty!
The 4228 would be pointing south into the back yard, no one would see it (and if they were looking into that 2nd floor bedroom window, I'd be worried about more than just an ugly antenna. ;-> ). I guess the 4228 would look like very strange window security bars.

Last edited by weblurker; 2005-06-01 at 09:40 AM.
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Old 2005-06-01, 09:39 AM   #7
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Quote:
Originally Posted by stampeder
But seriously, unless you are incredibly lucky to already have the perfect azimuth to the broadcasters you want when you first mount it in the window, you would have an aiming problem so maybe another idea is in order. If all you want are the CN Tower stations then fine.
Looking at the map on RemoteCentral.com

http://www.remotecentral.com/hdtv/index.html

it looks like the CN Tower and all the Buffalo stations are within a small arc of my location (I'm located at the north end of Toronto).

I've read how some HDTV users in Mississauga hardly ever use their rotators with their Yagi antennas and they're located directly west of the CN Tower. I suspect the CN Tower signals are so strong, pointing the 4228 at Buffalo would probably mean I'd get the CN Tower signals anyway.
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Old 2005-06-01, 11:26 AM   #8
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Quote:
Originally Posted by weblurker
The 4228 would be pointing south into the back yard, no one would see it...
I meant that it won't be pretty inside the house!!

Quote:
I've read how some HDTV users in Mississauga hardly ever use their rotators with their Yagi antennas and they're located directly west of the CN Tower.
At my store in Mississauga, I didn't even have a rotator on the antenna and could pick up the Toronto stations no problem at all with the antenna pointed directly toward Buffalo.

Last edited by JohnnyG; 2005-06-01 at 11:29 AM.
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Old 2005-06-01, 12:13 PM   #9
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Quote:
Originally Posted by JohnnyG
At my store in Mississauga, I didn't even have a rotator on the antenna and could pick up the Toronto stations no problem at all with the antenna pointed directly toward Buffalo.
Thanks. It's good to have another confirmation of CN Tower reception.

Quote:
Originally Posted by JohnnyG
I meant that it won't be pretty inside the house!!
Yes, I see what you mean. I was planning on mounting the antenna behind the curtains that are already there.

My friend lives in a townhouse/condo development that prohibits exterior dishes and antennas. I suggested that he mount the 4228 on an outside wall but decorate it with year 'round Halloween/Christmas stuff. The antenna would just look like a supporting structure for the decorations. But he'd look like one of those people too lazy to take down seasonal ornaments. Anyone who recognized the 4228 probably wouldn't turn him in. ;->

The 4228 looks like a wire mesh with eight bowtie elements. I wonder if you could mount similar bowtie antennas (but much larger) on the side of a house pointing at the transmitters and tie them together to form a giant 20' or 30' UHF antenna?

Last edited by weblurker; 2005-06-01 at 12:16 PM.
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Old 2005-06-01, 06:48 PM   #10
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Quote:
Originally Posted by weblurker
The 4228 looks like a wire mesh with eight bowtie elements. I wonder if you could mount similar bowtie antennas (but much larger) on the side of a house pointing at the transmitters and tie them together to form a giant 20' or 30' UHF antenna?
You could do that, but it wouldn't work.

TV and radio signals operate at very specific wavelengths (and frequencies, but we're not discussing those right now) so an antenna must be designed to capture those particular wavelengths while rejecting as many of the unwanted ones as possible. VHF and UHF antennas have quite different appearances and behaviours because the wavelengths are quite different in size, with UHF's being smaller.

Regarding your idea of building a huge antenna, its possible to "gang" two or more identical antennas together, but after adding the second one you start to run into the law of diminishing returns, and diminishing bank account too! Actually Channel Master hit a home run when they created the 4228 by ganging 2 4-bay UHF antennas into one. The grille on the 4228 is designed so that signals on very specific wavelengths are reflected to the bowtie elements.

Check out the "Do It Yourself Antenna" thread:
http://www.digitalhomecanada.com/for...ad.php?t=25677
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Old 2005-06-15, 01:59 PM   #11
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Default Can I split the signal from a CM4228?

Quote:
Originally Posted by Yaamon
Hi guys I am about the buy and install the Channel Master 4228 to hook up to a Sony KDF60XS955 that has a built in ATSC tuner.

For the bedroom going to buy a Toshiba 34HF85c using a Samsung Sir T451.

Can I just use a regular cable splitter 5 to 900mhz to feed each tv.
Depending on what your location is (proximity to target stations) there may or may not be enough signal strength from the antenna alone to provide for your main TV let alone a second one. That's why we need to know your location. Here's how you can test:

Hook up the CM4228 antenna to only your main TV for now and observe analog channels from the target city/location. If they are snowy, install a preamp to provide stronger over all gain with as little as possible "noise" added to the signal. There are different strength levels of preamps so don't just buy the strongest one. Again, your location would help us assess this. Assuming your analog signals are strong and clear either with or without a preamp, now you need to test if both TVs are driven well at the same time. Hookup your second TV with a splitter and as minimum an amount of connecting cable as possible. With both TVs turned on check the analog stations again on both TVs. If they're clear and strong, you are done. If they're snowy on 2 TVs when they used to be clear on 1, you need to get a distribution amplifier (an amplified splitter, not a preamp). A professional would be able to assess the situation for you if you need because there may be other things to consider, such as multipath.
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Old 2005-06-15, 06:28 PM   #12
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Opps sorry I live in Markham around McCowan and 14th Ave.

Planning to mount the antenna on the roof that the bottom of the antenna just clears the peak of the roof. At this position it has a clear view south and towards the CN Tower.

If I need to buy a good preamp for the antenna, what would you suggest.

Curious has anybody in Markham or near by picked up any channels from Rochester too, I know Buffalo is all I need ?

Thanks

Last edited by Yaamon; 2005-06-15 at 06:47 PM.
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Old 2005-06-15, 10:37 PM   #13
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Quote:
Originally Posted by Yaamon
Opps sorry I live in Markham around McCowan and 14th Ave.

Planning to mount the antenna on the roof that the bottom of the antenna just clears the peak of the roof.
Any chance of getting it a few feet higher? The roof will seriously weaken your reception if the antenna is too close to it, so I'd recommend mounting it so the bottom of the antenna is 2 to 3 feet above the roof at least.
Quote:
Originally Posted by Yaamon
At this position it has a clear view south and towards the CN Tower.
Okay that's great for the CN Tower stuff so you will certainly not need a preamp for those Canadian stations. Judging from posts in the GTA OTA thread you won't need a preamp for Buffalo either.

You should be able to aim the antenna about 40 degrees or so to the left of the CN Tower southwards and line up fairly well with Buffalo so that you get stations from both cities without rotating, but of course you can test the aim once its up and running. The CM4228 is terrific for that kind of aiming because its aperture has a main long distance lobe straight forward and some smaller lobes to the sides and back. With trial and error you should be able to find a happy compromise.

Regarding Rochester you could try mounting your new antenna on a rotator or go up there during good tropospheric DXing times and aim it there to see what happens. Keep in mind that Buffalo offers all the U.S. network stuff you'd want so Rochester is not necessary for you.

If both your TVs are not driven strongly by your antenna you can check here for info on distribution amplifiers.
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Old 2005-06-24, 03:05 PM   #14
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Ok guy got the antenna installed around lunch time. Damm it was getting hot today 37'C.

Me and a coworker installed it using a tripod mount. Will post the pics that I took when I get home tonight. The bottom of the antenna clear the peak of the roof by 2 foot.

Used a standard tripod mount, that comes with a 5 foot center pole. The cener pole also attaches to the roof and from there two additional legs around a swivel ring.

I did not try the two baluns and a combiner/splitter, by the way I see they sell low loss version on the net that has .5 DB loss.

I can get UHF 66 CKXT (Toronto 1 ) at max signal 10 bar on the Samsung out of 10. So I wont bother to clip the bows.

On the HDTV channels I can get all stations 10 out ot 10 on the signal strength bar except two.

Fox(WUTV) comes in at 6 to 8 and NBC(WGRZ) same 6 to 8 bar.

I know at night with the little Radio Shack indoor antenna 15 1880 I get no signal but at night it comes in especially after 12pm 5 to 9 bars.

If I position the antenna dead south it pulls in NBC at 8 to 10 bars but FOX disappears. All Toronto still at 10.

Would a preamp help this especially when I split the signal to run the two HDTV tv ?

What preamp do you recommend I should use.

Thanks.
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Last edited by Yaamon; 2005-06-24 at 09:07 PM.
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Old 2005-06-24, 03:10 PM   #15
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Quote:
Originally Posted by Yaamon
Would a preamp help this especially when I split the signal to run the two HDTV tv? What preamp do you recommend I should use.
Great results! I don't think you should worry about a preamp. If anything, you could overload your receiver, so don't go there at this point. If you're getting a lock on everything, let things be and enjoy.

When you connect the second TV try running them at the same time and see how well the antenna feeds them. Again, I don't foresee any problems, but you would not use a preamp at that point, you would look into an internal distribution amplifier. It sounds like you would have no need for one.

Test and let us know.
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