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Old 6-Jul-2015, 11:06 PM   #1
cpd
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Antenna Recommendation

I am considering cutting the cord and am experimenting with a HTPC set up and OTA. For the experiment, I bought a Mohu Leaf 30 (due to price and local availability) during my experimentation. The Leaf is mounted behind my TV (in a second floor room) on the slanted wall of our cathedral ceiling. I'd prefer not to raise ti so we don't have to stare at an antenna. The ceiling wall it is on is on the north face of our house near the east end of the house and is on the second story of the home. It is the house position nearest the transmitting towers. Here is the signal analysis.

The set up actually works really well, with one exception. FOX (6.1) is laggy and displays green pixelation/jitters. It has never cut out and gone black completely. That is the only station I have noticed issues with. Unfortunately, since I watch NFL, it is also an important station to fix. So I have a few questions:

1) Can someone recommend a different antenna that would work for all stations?
2) Or is the problem that I have it hidden behind the TV on a slanted wall?
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Old 6-Jul-2015, 11:12 PM   #2
ADTech
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Move the antenna and try again. The "best" location would be stuck on a window that does not have energy film or a metal window screen and faces the broadcast towers without your neighbor's house, a big tree, or a forest in front of it.

Move the antenna away from the TV set as they sometimes self-interfere when the antenna is too close.

The bottom line is that the antenna will tell you where it needs to be, it doesn't work the other way (where you tell it that it has to work where you want it).
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Old 6-Jul-2015, 11:37 PM   #3
rabbit73
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Welcome to the forum, cpd:

Quote:
The set up actually works really well, with one exception. FOX (6.1) is laggy and displays green pixelation/jitters.
I notice that the signal from Fox is coming in from a little different angle than the other signals. There could be a tree or some other object in its signal path.

Quote:
HTPC set up
What tuner are you using?

How well does the Leaf work with the TV tuner vs the HTPC tuner?

Does the TV tuner or the HTPC tuner have readouts of signal strength or more important signal quality to help you position the antenna?

I agree with ADTech, you must put the antenna where the best signal exists.

I suspect multipath reflections and tuner overload. WTMJ has a Noise Margin of 75.1 dB.



Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

You could test the overload theory by inserting an attenuator in the coax line.

You can add a length of coax using an F-81 adapter to try different antenna locations.

Quote:
Can someone recommend a different antenna that would work for all stations?
There are other indoor antennas that might work better because they have reflectors that make them more directional to reduce the pickup of reflections, but you might not like how they look. The Antennas Direct C2V would be one.
https://www.antennasdirect.com/store...-Complete.html
http://www.bestbuy.com/site/antennas...&skuId=6847298

I don't like computers, and have yet to find one that I would call user friendly. I only tolerate them for what they can do for me. I never have understood why anyone would want to watch TV on a computer instead of a TV.

I see a lot of trees in your area. See attachment 1.
http://www.hdtvprimer.com/antennas/siting.html
scroll down to Trees and UHF

I also see that you have some strong local FM signals that might interfere with TV reception. See attachment 2. You should insert an FM filter in the coax line.
http://www.mcmelectronics.com/produc...-FM-88-/33-341
http://comingsoon.radioshack.com/rad...l#.VZskAzjbJLM very slow link
Attached Images
File Type: jpg cpdTVFtrees (2).jpg (207.0 KB, 478 views)
File Type: jpg cpdTVF FM est.JPG (98.4 KB, 479 views)
File Type: jpg NMChartC.jpg (71.3 KB, 981 views)
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Last edited by rabbit73; 7-Jul-2015 at 1:26 AM.
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Old 7-Jul-2015, 1:09 AM   #4
cpd
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Quote:
Originally Posted by ADTech View Post
Move the antenna and try again. The "best" location would be stuck on a window that does not have energy film or a metal window screen and faces the broadcast towers without your neighbor's house, a big tree, or a forest in front of it.

Move the antenna away from the TV set as they sometimes self-interfere when the antenna is too close.

The bottom line is that the antenna will tell you where it needs to be, it doesn't work the other way (where you tell it that it has to work where you want it).
Thanks. I understand the concept of placing the antenna where it needs to be. I was just hoping to keep it concealed. I read (and it may be inaccurate), that DTV signals are really either on or off - reception or black screen. I read that the green pixelation and lag meant I was right on the cusp of good reception. I was hoping that a better antenna might solve the problem while still being concealed.
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Old 7-Jul-2015, 1:17 AM   #5
rabbit73
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Quote:
I read that the green pixelation and lag meant I was right on the cusp of good reception.
We call it the "Digital Cliff."
Quote:
I read (and it may be inaccurate), that DTV signals are really either on or off
Correct.



Attached Images
File Type: jpg AnalogVSDigital2.jpg (108.6 KB, 947 views)
File Type: jpg NoiseMargin.jpg (60.1 KB, 1006 views)
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Old 7-Jul-2015, 1:31 AM   #6
cpd
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So one interesting thing. FOX is fine tonight. The two prior times I tuned in that channel, I was watching the US women's world cup. Could the contact have caused the issues?
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Old 7-Jul-2015, 1:36 AM   #7
rabbit73
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OTA signals are constantly changing in strength.
Quote:
Could the contact have caused the issues?
What contact? If you.had a bad contact it would probably affect all channels. If it was intermittent, it would be difficult to find.
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Old 7-Jul-2015, 1:42 AM   #8
cpd
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Quote:
Originally Posted by rabbit73 View Post
OTA signals are constantly changing in strength.
What contact? If you.had a bad contact it would probably affect all channels. If it was intermittent, it would be difficult to find.
Sorry - I did not proof read. I meant "content". i.e. could live sports have been the issue.
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Old 7-Jul-2015, 1:49 AM   #9
rabbit73
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Oh, OK. Usually the best cameras are used for sports. But, there could have been a technical problem with the network feed, especially if it was through satellite.
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Old 7-Jul-2015, 2:14 AM   #10
ADTech
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Quote:
I read (and it may be inaccurate), that DTV signals are really either on or off - reception or black screen
It would be more accurate to describe it as "either they're perfect (enough) or they aren't". When they aren't, the reception defect will manifest in any number of manners, depending on the tuner's capability and design, and on the relative degree of signal impairment. Typical manifestations of an impaired signal include pixelization, macro-blocking, audio dropouts, frozen images, black/blue screen, "Weak/No Signal" messages, etc.
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Old 7-Jul-2015, 4:32 PM   #11
cpd
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Quote:
Originally Posted by rabbit73 View Post

Quote:
What tuner are you using?

How well does the Leaf work with the TV tuner vs the HTPC tuner?

Does the TV tuner or the HTPC tuner have readouts of signal strength or more important signal quality to help you position the antenna?
I am currently using a loaner AverMedia AverTV Combo PCI-E tuner card, with video output by a nice graphics card to my TV. If this all works out, I will eventually purchase some form of multi-channel tuner card so I can record more than one channel at a time. I have not compared the internal TV tuner with the card, but if the problem persists I may. But even if that is better I will need a solution because I need a DVR, so I cannot use the TV's internal tuner.

I will play around with tuner cards software and see if it has strength/quality readouts.

Quote:
I agree with ADTech, you must put the antenna where the best signal exists.

I suspect multipath reflections and tuner overload. WTMJ has a Noise Margin of 75.1 dB.



Interpreting Noise Margin in the TV Fool Report
http://www.aa6g.org/DTV/Reception/tvfool_nm.html

You could test the overload theory by inserting an attenuator in the coax line.

You can add a length of coax using an F-81 adapter to try different antenna locations.

There are other indoor antennas that might work better because they have reflectors that make them more directional to reduce the pickup of reflections, but you might not like how they look. The Antennas Direct C2V would be one.
https://www.antennasdirect.com/store...-Complete.html
http://www.bestbuy.com/site/antennas...&skuId=6847298
I appreciate the information, but a lot of this is well over my head. Based on the post about the Digital Cliff, it seems I may be just a bit off. Would you recommend a new antenna anyway? I don't want to put anything on the roof, and that clearstream seems like a monster for indoor use (I am not sure I could get my wife to agree to it). Are there other good options you can recommend?

Quote:
I don't like computers, and have yet to find one that I would call user friendly. I only tolerate them for what they can do for me. I never have understood why anyone would want to watch TV on a computer instead of a TV.
For me, it is the least expensive and most versatile way to incorporate a DVR, without exorbitant TV guide fees or hardware limitations. Other than the reception, it was actually easy to set up and works seamlessly with my remote. The Windows Media Center interface is pretty well polished too.

Quote:
I see a lot of trees in your area. See attachment 1.
http://www.hdtvprimer.com/antennas/siting.html
scroll down to Trees and UHF

I also see that you have some strong local FM signals that might interfere with TV reception. See attachment 2. You should insert an FM filter in the coax line.
http://www.mcmelectronics.com/produc...-FM-88-/33-341
http://comingsoon.radioshack.com/rad...l#.VZskAzjbJLM very slow link
The largest/oldest tree in my city covers this corner of the house. Believe me I wish they'd cut it down. I assume trees are just something you need to work around with antenna placement.
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