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Old 14-Jan-2010, 8:24 PM   #1
zuiko
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Recommendations please

Channel | Signal | Dist
32 (4.1) | 11.6 -79.3 2Edge | 67.5
35 (5.1) | 10.1 -80.7 2Edge | 67.5
11 (11.1) | 6.2 -84.7 2Edge | 67.5
9 (9.1) | 4.3 -87.9 2Edge | 68.1


I need recommendations on equipment needed to receive these (digital) signals. They are all coming from the same place (within 1 degree) so a unidirectional would be fine. The terrain is pretty flat.

Would a big high gain VHF/UHF antenna in the attic with some kind of pre-amp be enough or would it have to go on the roof or would I need some kind of tower?

Would I be better off going with two antennas (a UHF and a VHF) instead of one?

Thanks.

Last edited by zuiko; 14-Jan-2010 at 8:31 PM.
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Old 14-Jan-2010, 11:21 PM   #2
mtownsend
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Hello and welcome!

Quote:
Originally Posted by zuiko View Post
Would a big high gain VHF/UHF antenna in the attic with some kind of pre-amp be enough or would it have to go on the roof or would I need some kind of tower?
BTW, for future reference, you can simply copy/paste the site address for the page with your report (the page with the radar plot and tables). This will let the rest of us see your report without having to re-type anything. The reports themselves hide your exact location, so you do not need to worry about giving out your address if you don't want to.



Are the channels you listed the strongest ones on the list? I just want to make sure there aren't any super strong stations nearby that can make reception of more distant stations difficult (e.g., signal overload, adjacent channel interference, etc.).

Also, are there any low VHF (ch 2-6) channels that are on your list that you might be interested in?

Do you plan to split the signal to multiple TVs?



Since the stations you listed have Noise Margins in the 0-15 dB range, then the typical solution for this would be a rooftop antenna. If you have a "low loss" attic (minimal material that might block signals) and enough room for a good sized antenna, you can probably get away with one of the larger antennas in your attic. The amount of signal loss through your attic is an unknown variable, so your degree of success will depend on that.

If you do go with a rooftop installation, you can probably go with a slightly smaller antenna.

Since the four channels you listed are in the range of 7 to 69, you should get good results with an antenna in the Antennacraft HBU-22, -33, -44, -55 family of antennas or the Winegard HD7694P, HD7695P, HD7696P, HD7697P, HD7698P family of antennas (these range from small to large).

If the antenna was on the roof, I think an HBU-33 or HD7694P would be about the right size for signals in your range. In the attic, you probably should go one size higher to make up for the reduced signal strength.



Quote:
Would I be better off going with two antennas (a UHF and a VHF) instead of one?
It is also possible to use two separate antennas for UHF and VHF. Either solution will work. I don't see any particular need to go with two antennas, but it may be worth investigating just to see if the "fit" of the antenna(s) can be improved with separate antennas. You might find that a compact UHF-only antenna combined with a large VHF yagi can be arranged better within the space of your attic.

The two antenna solution can outperform the combo antenna solution, but your signals are strong enough so that I don't think this added performance is absolutely necessary.



As long as you don't have any strong local signals that might overload an amp, then a pre-amp is probably a good idea for your situation.

If you have separate VHF/UHF antennas, then a pre-amp like the Channel Master 7777 would be ideal because it has the option of taking two separate inputs based on frequency band.

If you have two antennas and a pre-amp that doesn't have separate band inputs, be sure to combine the antennas with a UVSJ instead of using a plain combiner/splitter. The UVSJ is a "diplexer" that can merge different frequency bands into one coax with less loss than a simple splitter/combiner.
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Old 15-Jan-2010, 2:36 AM   #3
zuiko
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Quote:
Originally Posted by mtownsend View Post
Are the channels you listed the strongest ones on the list? I just want to make sure there aren't any super strong stations nearby that can make reception of more distant stations difficult (e.g., signal overload, adjacent channel interference, etc.).
Pretty much. There's only one yellow station on the list and the bearing for that station it is at about 100 degrees relative to the ones I want to get. It's on channel 12.

Quote:
Also, are there any low VHF (ch 2-6) channels that are on your list that you might be interested in?
There are no Low VHF stations in the area

Quote:
Do you plan to split the signal to multiple TVs?
Nope. I only plan on having one device actually connected to the antenna (a DVR) and I will split the output (HDMI) of that device.

Quote:
Since the stations you listed have Noise Margins in the 0-15 dB range, then the typical solution for this would be a rooftop antenna. If you have a "low loss" attic (minimal material that might block signals) and enough room for a good sized antenna, you can probably get away with one of the larger antennas in your attic. The amount of signal loss through your attic is an unknown variable, so your degree of success will depend on that.
I would probably try the attic first then since I do not have any metal (foil backed insulation, etc) in the roof other than nails. It is shooting through plywood, tar paper, and asphalt shingles. The (paper-faced fiberglass) insulation is below where the antenna would be mounted so the signal doesn't have to go through that.

How would I go about actually mounting it in the attic? Can I just hang it up from the boom with fishing line or do I need to get kind of short mast and plate? Does it make any difference if it is upside down or upside right? Am I still going to need to run a grounding wire outside to a ground spike if the antenna is in the attic? Grounding would be a lot more problematic in the attic.

Quote:
Since the four channels you listed are in the range of 7 to 69, you should get good results with an antenna in the Antennacraft HBU-22, -33, -44, -55 family of antennas or the Winegard HD7694P, HD7695P, HD7696P, HD7697P, HD7698P family of antennas (these range from small to large).
I'm thinking I would go with the HD7698P (I would rather buy too big than too small) with the AP-8275. There is no advantage upgrading to the HD82000U since I have no VHF-Lo stations, right?

Thanks for the great info. It is a huge help.

Last edited by zuiko; 15-Jan-2010 at 3:39 AM.
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Old 15-Jan-2010, 9:52 AM   #4
mtownsend
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Thanks for all the detailed info. That helps a lot.

Quote:
Originally Posted by zuiko View Post
How would I go about actually mounting it in the attic? Can I just hang it up from the boom with fishing line or do I need to get kind of short mast and plate?
Most antennas come with mounting brackets built into the boom that makes it easy to attach to a mast (usually a round pipe about 1.25 to 1.5 inches in diameter). The masts themselves can be attached from the floor up or from the top down using some pretty simple mounting brackets. Here's a picture of a basic mast mount (Channel Master 3078) as an example:


There are many creative ways to physically place the antenna in the attic (including your idea with fishing line). The nice thing about using a mast is that it's simple to work with, the antenna does not move around while you're working with it, they are sturdy, and they give you an easy way to make rotational adjustments as needed (to optimize antenna aim once everything is installed).


Quote:
Does it make any difference if it is upside down or upside right?
No. The antennas themselves are usually symmetric in both the horizontal and vertical directions. There is no discernible difference whether the antenna is upside down or not.

However, it is important that the antenna remain horizontally polarized (all TV broadcasts are horizontally polarized signals), meaning that the main antenna elements should be roughly parallel to the horizon as opposed to being vertically oriented.



Quote:
Am I still going to need to run a grounding wire outside to a ground spike if the antenna is in the attic?
No.



Quote:
I'm thinking I would go with the HD7698P (I would rather buy too big than too small) with the CM-7777. There is no advantage upgrading to the HD82000U since I have no VHF-Lo stations, right?
Yes, exactly. The HD8200U is both very long and very wide. The wide antenna elements at the back of the antenna that deal with low VHF channels will make it a lot harder to work with if you are cramped for space. If you do not need low VHF, then you can get roughly similar performance out of the much narrower HD769xP family of antennas.

Please note that the HD7698P is over 14 feet long and about 4.5 feet wide. A bigger antenna does give you more signal, but you also have to be pragmatic about what will actually fit (and can be rotated to the correct direction) within the space you have.

If the antenna was outside on the roof, I was thinking that an HD7694P would be sufficient, given the signal strengths you indicated. Going up one size for an attic installation is also probably good enough (since your attic does not sound like a big signal stopper). Going up two sizes (to an HD7696P) should give you some extra margin for comfort. Going up four sizes (to an HD7698P) may be a bit much.

If you don't mind the extra cost, have plenty of room to spare, and just want to make absolutely sure that you get the maximum possible signal, then by all means, go as large as you feel comfortable with.

Yes, the CM 7777 is a good idea. It makes sure that any signal gathered by your antenna does not get lost to things like cable loss or splitters (in case you decide to add more receivers later) that come after the amp. It probably isn't critical right now since you're only planning on sending this to one receiver, but a pre-amp is another way to add some safety margin and robustness to your setup.

Last edited by mtownsend; 15-Jan-2010 at 9:57 AM.
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Old 19-Jan-2010, 5:56 AM   #5
zuiko
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Thanks. I got the antenna and set it up in the attic (it is huge and barely fit) and the channel scan picked up 18 digital channels including everything I was shooting for, though the weakest ones are breaking up sometimes -- probably because of bad aim (I could easily be as much as 5 degrees off). I'm not sure how to precisely aim it though, since the signals are all digital and reception is pretty much all or nothing. My TV does not appear to have any sort of signal strength indicator. Is there some other trick that can help in this case?

Last edited by zuiko; 19-Jan-2010 at 6:45 AM.
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Old 19-Jan-2010, 3:25 PM   #6
mtownsend
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Which channel is breaking up? (If you can provide a link to your tvfool report, we will have a better understanding of your signal situation)

As for aiming the antenna, you can start with a compass and then try different 5 or 10 degree increments to look for improvement. The antenna beam width is pretty wide to begin with (probably about 30 degrees across), so sweeping across a 90 degree sector ought to give you an idea of where the center of the sweet spot is.

If you have missing channels that don't show up at all, then look for other channel transmitting from the same tower that you do get. If the other channels are aimed correctly, then it's probably about as good as you'll get for the missing channel.

If you're trying to get channels that are outside the main beam of the antenna, it might be more difficult. If the desired transmitter clusters are within 30 degrees of each other, you might be lucky enough to get all of them to fit in the antenna's beam pattern. If not, then you'll either need to deal with an antenna rotator, an A-B switch, or think about combining multiple antennas.
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Old 19-Jan-2010, 3:54 PM   #7
zuiko
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All the channels are within 1 degree of each other so that isn't a problem. It finds them all (and then some) so that isn't a problem either. The issue I have is that everything will be fine for 30 minutes then the signal will just randomly break up or get lost. If I change to another channel and then back it will often fix it. Seems to be an issue with all channels. So maybe the aiming is borderline (but I am well within 15 degrees... at most I am off 5 degrees). Maybe it is the tuner on the TV... it is obviously not a high end model since it doesn't even have a signal strength meter.
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Old 19-Jan-2010, 4:42 PM   #8
mtownsend
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What is the make/model of TV? Sometimes the signal meter feature is hidden or put in a non-obvious location.

Occasional breakups across all channels seems very suspicious. It that is happening, then it would point to something local (near you as opposed to something happening on the broadcaster side) affecting your TV or signals. Are you aware of any ham radio operators in your neighborhood (look for really big antennas on neighbors' roofs)? Are you aware of any noise/glitches on your power lines (perhaps caused by appliances or power tools). Are there any nearby airports?
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Old 19-Jan-2010, 6:34 PM   #9
zuiko
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It is an Akai 720P Plasma I got a few years ago. It is a pretty cheap TV. I don't know who really made it. I have never used the tuner on it before because I always had satellite so I'm not sure how good it is.

Not sure about HAM radio but not that I know of. There some tiny general aviation airports as close as 15 miles or so, one of which would be close to the bearing the antenna is on.

I also occasionally get some slight sound garbling when the picture continues to looks fine. This happens a little more often than the visual signal dropping. I'm not sure if that is just a less extreme version of the same issue or what.

Last edited by zuiko; 19-Jan-2010 at 6:43 PM.
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Old 19-Jan-2010, 7:53 PM   #10
zuiko
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OK I got an electronic converter box to better debug the issue and it has 3 meters: signal strength, signal quality, and symbol quality. Signal strength is pretty good... 94%-100% and pretty stable.

Signal quality is a lot worse. It is much less stable moving +/- 10% all the time and varies a lot by channel. One channel (9) ranges from 45-85%. Some are in the 80s and 90s. As soon as they drop below 50% it would break up and symbol quality would drop to 0%. This would happen with signal strength still at 95%. I tried removing the pre-amp from the system and all that did was drop my signal strength by about 30 points. Didn't seem to have any positive effect on signal quality. What should I look at to improve this?

Last edited by zuiko; 19-Jan-2010 at 9:41 PM.
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Old 19-Jan-2010, 11:11 PM   #11
mtownsend
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Have you tried moving and/or turning the antenna? Since the antenna is in the attic, there may be some metal objects close enough to the antenna to affect its behavior.

Unfortunately, I think the main issue is that the antenna is in the attic instead of on the roof. The Noise Margins you originally posted were in the range of 4-12 dB. These are normally a bit too weak to be handled with an attic antenna. A pre-amp will make you see more signal strength (to deal with cable loss, splitters, etc.), but it cannot fix the inherent shortcomings of the antenna itself. Boosting a weak "muddy" signal gives you a strong "muddy" signal, which isn't really much help. Installing the antenna outside ought to clean up the signal.

The hope was that you might get lucky and have an "easy" attic install that behaves almost like a rooftop install. Based on your testing, it looks like that might not be the case.



If you still feel like doing some experimentation, it would be interesting to see if the signal dropouts/glitches are periodic or completely random. If you use a stopwatch to measure the time between glitches (either audio or video), do you see any pattern? Is the pattern the same on all the channels you receive? Is the pattern the same during the day or night?

Under normal calm weather, one would expect your signals to be relatively stable, with only very slow variations (caused by slowly changing atmospheric conditions). If your best channels (normally showing a quality of 80-90%) drop out every few minutes (quality suddenly dropping below 50%), then it would indicate something abnormal is happening (radar from airport? planes/cars/trucks going by? other local broadcasts? power tools/arc welding, or other local interference?).

If there's any way to figure out the cause of the signal disruptions, we at least have a shot at knowing what kinds of work-arounds to try.



Sorry to say this, but your best overall solution may be to give-in and move the antenna to the roof. No matter what is causing the signal dropouts, a rooftop antenna will add several dB of signal margin, and this will give your receiver more to work with.
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