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Old 30-Jan-2010, 1:17 AM   #1
Jeffb
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Join Date: Jan 2010
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Antenna Advice in Suburban Atlanta

http://www.tvfool.com/?option=com_wr...c72388eee1150a

I’m planning on dropping basic cable service in favor of OTA for our two TVs, so began researching antennas and wandered into TVFool a few days ago. You are really providing a great service. I have been reading through the forums and have learned a lot, but still have some questions about how to proceed.

I’m only interested in receiving the local Atlanta channels, primarily the 4 major networks plus the 2 PBS stations (all within the first 10 channels on the list). The transmitters are all within 25 miles. Am I a good candidate for an attic installation? We have a single story house with asphalt shingles. No tall buildings around. There are several fairly large trees next to my house, but the antenna will be below the canopy and aimed between the trunks. There is a grove of large hardwood trees on the same general azimuth but approx. 200 yards away.

If I understand the difference between the “real” and “virtual” channels, our ABC and FOX channels were VHF when broadcasting in analog (channels 2 & 5) but switched to UHF channels for the digital changeover (39 & 27 respectively). That leaves 2 of my desired channels in the VHF band (8 & 10), so I guess that means I need a combination VHF/UHF antenna.

All of my desired channels are within 8 degrees of azimuth (301 - 309 magnetic), except channel 8 (336 degrees), but that is also the closest transmitter at 16 miles. I’m guessing I would not need a rotor, but how best to aim the antenna?

All of my desired channels show a line-of-sight path, which is self-explanatory, except channel 8 which is listed as single edge diffraction. I have no idea what that means or how it might affect reception. Please explain, as this is our most-watched channel.

My inclination is to buy an antenna and try it in the attic first. This would have the advantage of being almost directly above both TVs, resulting in very short coax runs. If reception is unacceptable, I would consider moving the antenna outside using a ground-mounted mast and installing it where the existing cable enters the house. This would allow me to use the existing building cables and grounding wire. It would also keep me off the roof which would make my wife happy!

So that’s my situation. Any advice on which antenna to buy and how to proceed would be greatly appreciated.
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Old 30-Jan-2010, 4:50 AM   #2
mtownsend
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Hello and welcome!

Quote:
Originally Posted by Jeffb View Post
Am I a good candidate for an attic installation? We have a single story house with asphalt shingles. No tall buildings around. There are several fairly large trees next to my house, but the antenna will be below the canopy and aimed between the trunks. There is a grove of large hardwood trees on the same general azimuth but approx. 200 yards away.
Since your channels are so strong, there's a great chance that an attic antenna will work.



Quote:
If I understand the difference between the “real” and “virtual” channels, our ABC and FOX channels were VHF when broadcasting in analog (channels 2 & 5) but switched to UHF channels for the digital changeover (39 & 27 respectively). That leaves 2 of my desired channels in the VHF band (8 & 10), so I guess that means I need a combination VHF/UHF antenna.
Yep, you got it! The virtual channels are what you see displayed on your TV, but it's the real broadcast channels that matter when it comes to picking an antenna.



Quote:
All of my desired channels are within 8 degrees of azimuth (301 - 309 magnetic), except channel 8 (336 degrees), but that is also the closest transmitter at 16 miles. I’m guessing I would not need a rotor, but how best to aim the antenna?
Correct again. Most antennas have a fairly wide beam width. The "sensitive zone" in front of the antenna is usually between 30 and 60 degrees wide. Since all of your channels are within about 30 degrees of each other, I don't think you'll have any problem getting them all within the sweet spot of the antenna.



Quote:
All of my desired channels show a line-of-sight path, which is self-explanatory, except channel 8 which is listed as single edge diffraction. I have no idea what that means or how it might affect reception. Please explain, as this is our most-watched channel.
I don't see 1Edge showing up in your report now, so perhaps you re-did the report at a different location or at a different height.

In any case, single edge diffraction means that the signal must "bend" over the top of one terrain obstruction. All radio waves can bend, or diffract over obstacles to a certain degree. If you are just barely within the "shadow" of a terrain obstruction, there's still a good chance of getting very strong signals. The "deeper" you get into the shadow, the less signal you will see. The signal analysis tools take this into account, so if it's still saying that you are getting strong signals, then the terrain obstruction must not be that bad.

In most cases, it doesn't make that much difference if the signal is getting to you via LOS or via diffraction, as long as it's strong enough to be picked up. There are some situations where diffraction can make things more difficult. This might happen if there are lots of trees or tall buildings along the ridge-line where the diffraction is taking place. This might make your signal pick up more multipath interference than the LOS case.



Quote:
My inclination is to buy an antenna and try it in the attic first. This would have the advantage of being almost directly above both TVs, resulting in very short coax runs. If reception is unacceptable, I would consider moving the antenna outside using a ground-mounted mast and installing it where the existing cable enters the house. This would allow me to use the existing building cables and grounding wire. It would also keep me off the roof which would make my wife happy!
Sounds like a great plan. I'm pretty sure you can get an attic installation to work. I'd recommend an antenna like the Winegard HD7694P or the Antennacraft HBU-33. Both of these are designed to handle high-VHF and UHF (channels 7-69), which is all that you need, and they should be small enough to fit inside most attic spaces. Aim the antenna at compass heading 315 degrees and you should be able to pick up all your stations (these antennas have a relatively wide beam width of around 50 degrees).

The antennas are designed to clamp onto some kind of mast (any kind of vertical pipe up to 1.5 inches in diameter). In most attics, you can hang a short section of mast from one of the joists overhead using some simple brackets. Try to keep the antenna away from other objects, especially conductive materials like metal bracing, ducts, foil-backed insulation, etc.

I also recommend that you DO NOT install any amplifiers in your situation. Your signals are too strong to be handled by most amps, so adding one will probably make things worse rather than better. At these distances, an amp simply isn't required.



Good luck!
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Old 31-Jan-2010, 3:27 PM   #3
Jeffb
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Thanks! I ordered the Winegard antenna yesterday. Will let you know the results after I get it installed.
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Old 5-Feb-2010, 3:47 PM   #4
Jeffb
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Smile

The antenna arrived yesterday afternoon. I had already hung a mast section in the attic, so installation took less than a half hour. Reception quality is excellent! This morning I added a splitter and connected my FM receiver. My wife will not miss the indoor antenna that was thumb-tacked to the wall. All that remains is to buy a digital converter for the analog set in the bedroom, and it's "Good bye Comcast!". Thanks so much. I'm a happy camper.
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Old 5-Feb-2010, 3:59 PM   #5
mtownsend
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Glad to hear it! Congrats!

Did you have any HD content through Comcast? It might be interesting to do a comparison of OTA HD quality vs. cable before you turn it off.
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