Antenna help

[Rev]

My analysis is here (http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d46aea27a8346f3).

I'd like advice on what antenna setup I need to get all the local major network stations found in the green, and the one (48) in the yellow (7 total channels if possible). I'd like to use a single antenna if possible, and I'd prefer to put the antenna in the attic. This could mean the cable run could be as short as ~25 feet. I am concerned reception may be affected by all the metal ducts and A/C unit within close proximity and between the antenna and the signal source. I could either raise the antenna or run a much longer strand of cable to avoid this. Longer cable may dictate the need for an amplifier.
Regarding cable, is it critical to have a very specific kind, or is any type of coax really sufficient?
Note: I have tried a couple different antennas in the living room, a cheap loop/rabbit ear combo and a homemade antenna similar to this (http://www.tvantennaplans.com/). Both would get some channels, but not all, and both seemed to be quite sensitive to direction. I now have the homemade antenna in the attic. It gets multiple channels, but seems ultra sensitive to direction, and note again concern with possible interference mentioned above.
Thanks.

[GroundUrMast]

Metal ducts near an antenna are a problem worth avoiding. Metal reflects signal and if close to the antenna, detunes it.

A well made 4-bay UHF antenna (Antennas Direct DB4e for example) mounted clear of obstructions (outdoors preferably) would be a very good option. You may need to add a second antenna to make WTZT reliable. An Antennacraft Y5713 is designed to receive real CH-7 through CH-13 would be my choice. You can combine the two antennas into a common cable by using a UHF/VHF combiner. The Antennas Direct EU385CF include the combiner and a weather proof housing.

[teleview]

A Simple reception situation.

Looking at the Tvfool Digital Current Plus Pending Applications Included Channel List.

For reception of the Digital Broadcast Tv stations/channels down the channel list in the Green and Yellow reception zones.

With on antenna aimed in one direction.

Above the roof in such a manner that the roof and building are not impeding and blocking reception in the directions of , East , South East , South , South West , North West.

Install a ANT751 or Antenna Craft HBU11 antenna aimed at about 150 degree magnetic compass direction.

Here is how to aim antennas , http://www.kyes.com/antenna/pointing/pointing.html.

Use a Old School magnetic compass to aim the antenna.

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Install a Winegard , LNA-100 'Boost' amplifier.

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For 1 Tv connected use No splitter.

For 2 Tv's connected use a simple common 2 way splitter.

For 3 Tv's connected use a simple common 3 way splitter.

Install the LNA-100 before any splitter.

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As always , trees and tree leaves , plants and plants leaves , have a Negetive effect on broadcast Tv reception and so do buildings and other obstructions including your own roof and house in the directions of reception.

The Best Practice is to install the antenna at a location that has the least amount to no amount of obstructions of any type or kind in the directions of reception including your own roof and house.

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The Tv/s Must Channel Scan for the , OTA=Over The Air , Digital Broadcast Tv stations/channels , often named the 'Air Channels' or 'Antenna Channels' in the Tv Setup Menu because the Tv transmissions travel through the Air from the transmitting antenna to the receiving antenna.

Some digital tv's will Automatic channel scan for cable tv channels.

DO NOT channel scan for cable tv channels.

Go into the Digital Tv Setup Menu and select 'Air Channels' ~ 'Antenna Channels'.

Scan for channels.
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Digital tuners can develop - Digital Glitches - that are not cleared out with simple channels scans.

To clear the tuner of non correct channel information.

Do Double Rescan ,

1. Disconnect antenna coax from Tv.

2. Do a channel scan.

3. Unplug Tv from power.

4. Wait a minute or so.

5. Plug Tv into power

6. Scan for channels

http://www.wchstv.com/DoubleReSacnAlert.pdf.

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[Rev]

Thank you very much for your reply. I am not concerned with WTZT, so I will probably opt out of the second antenna.
Understanding that outdoors would be preferred...
If I mount the suggested UHF antenna in the attic *clear of all the metal surfaces,* is there a rule of thumb that can be used to tell if I need an amp? I ask because the cable run required to get my antenna on the other side of the duct work, etc. would be quite a bit longer than I have now. Also, I assume RG6 would be fine?
Thanks again.

[GroundUrMast]

Thank you very much for your reply. I am not concerned with WTZT, so I will probably opt out of the second antenna.
Understanding that outdoors would be preferred...
If I mount the suggested UHF antenna in the attic *clear of all the metal surfaces,* is there a rule of thumb that can be used to tell if I need an amp? I ask because the cable run required to get my antenna on the other side of the duct work, etc. would be quite a bit longer than I have now. Also, I assume RG6 would be fine?
Thanks again.

Here is a simple test to determine if an amplifier will help. http://forum.tvfool.com/showthread.php?t=13646

RG-6 is fine. There's no reason to pay for quad-shield. For planning purposes, RG-6 has about 6 dB of attenuation at the highest UHF frequency. VHF loss is roughly half that of UHF. Here are examples of how to calculate net noise margin. http://forum.tvfool.com/showthread.php?t=109

[Rev]

I installed the RCA ANT751 today. A major factor in that decision was the fact that I could buy it locally and have a more me-friendly option to return if desired. I installed it in the attic, but above and/or on the clear side of all ducts, metal, etc. Only the roof and shingles should be between my antenna and clear air. There is a 50ft run of RG6 between my antenna and the wall outlet, and a ~6ft run of CATV cable (didn't have a short RG6 handy) between the outlet and my TV. I can get all the channels I want (actually 20 in all, including WTZT) except for NBC, Channel 48. I want this channel.
I'm guessing I can't get it due to one of two things, (1) the antenna is not pointed correctly (I have it pointed due East), or (2) noise margin is too low. Probably #2.

Starting Noise Margin = 30.6 dB
Antenna gain = 0 dB est. (can't find it anywhere)
Cable loss = 3 dB per calculation + fudge factor for union and second cable (Should there be more for the outlet and other cable section?)
Building loss = 20 dB est. (help?)
Receiver Noise Figure = 6 dB (estimated because not shown in manual)
==========
Net residual Noise Margin = 1.6 dB

Now, I think I've answered my own question, so long as all the estimations are reasonable. Clearly a 1.6 margin is unacceptable. Would like an expert verification, though. Perhaps even if I am slightly off, it is still too bad...

Also,
-Does distance between antenna and roofing material matter? I'd be very interested to hear why, if so.
-Would like verification that the slight difference in pointing angle to the NBC antenna is likely not causing a problem here.

Thanks again.

[GroundUrMast]

Try 'testing' reception outside. That may help you decide if an antenna with higher performance is needed, or if you need to escape the attic.