Question about OTA and Antenna

[InDashMP3]

Newbie just getting ready to take the HD plunge here. I have Dish Network and will be getting one of the 942 receivers. I am moving to a place that will be 57.2 miles away from the broadcasts of the Washington D.C. local ABC,CBS, and NBC stations. Strange thing is, when I put in my current address in antennaweb, I am 22 miles away and these chanels show as WJLA-DT, WUSA-DT, and NRC-DT, however the same call letters do not have the -DT (Digital?) designation from my new address. What is the distance limitation for digital broadcasts and why would one address show the channels as digital broadcasts, but the other will not? I really want to get HD feeds, and need help selecting an antenna that will work well at 57.2 miles (VHF). I would prefer the antenna be installed in my attic. Any help?

[Jim5506]

Effective distance for digital depends on (A) station power, (B) terrain, and (C) antenna.

The only factor you control is C. Antennaweb is usually conservative in their estimates.

Talk to people in the area you are moving. Look around for antennas, does anyone there receive digital OTA. At nearly 60 miles, you'll need a large, outdoor, amplified UHF antenna on a mast or tower.

Forget the attic thing, never gonna happen.

The mast can help with terrain problems.

The amplifier is needed because of the distance, especially if the channels are UHF (which WRC-DT, WUSA-DT, and WJLA-DT are).

[Bill Johnson]

Forget the attic thing, never gonna happen.At the risk of being hounded off this forum as I virtually was at another one, I believe Jim has good advice except about the attic. There are so many variable attic situations and an attic antenna has so many advantages that I always consider it worth a try. Nothing ventured, nothing gained!

My attic reception comes from such huge distances and I probably owe a lot to my high elevation. But when the lightning crashes and the winds howl, what a relief to know that CM 4228's under my roof!

[Antennaguy]

I tend to agree with Bill Johnson. Either 57 or 22 miles from the broadcast tower does not sound that far when I am used to far west Texas distances. Also, I believe it is flat around D.C.
Weather is always a concern, at least here with tall outdoor antennas. Unless the roof is metal, I would try the attic mount with a good UHF only antenna ( I see no listing for any digital VHF in your area ), and avoid amplifiers as they can easily overpower strong signals causing all digital stations be overpowered due to multipath interference.
You could surely do some type of experiment and test the difference in signal quality between the attic mount and holding the antenna out a window or some other temporary outdoor position. I find it easier to judge antenna performance based on the old analog stations as it is obvious when reception improves,verses the digital "signal quality" meters included with HD set top boxes.
Best of luck, there is no harm in being flexible and realizing that you may have to play around with it for a while.

[Tower Guy]

Newbie just getting ready to take the HD plunge here. I have Dish Network and will be getting one of the 942 receivers. I am moving to a place that will be 57.2 miles away from the broadcasts of the Washington D.C. local ABC,CBS, and NBC stations. Strange thing is, when I put in my current address in antennaweb, I am 22 miles away and these chanels show as WJLA-DT, WUSA-DT, and NRC-DT, however the same call letters do not have the -DT (Digital?) designation from my new address. What is the distance limitation for digital broadcasts and why would one address show the channels as digital broadcasts, but the other will not? I really want to get HD feeds, and need help selecting an antenna that will work well at 57.2 miles (VHF). I would prefer the antenna be installed in my attic. Any help?

The fact that the -DT does not appear is that antennaweb's calculations indicate that you are too far away and/or terrain limited and can't receive the DTV signals. It is still possible to receive DTV when antennaweb says that you can't, but don't expect to do so with an indoor antenna, even high in the attic.

The presumption in antennaweb is for a UHF antenna gain of 10 db with no preamp and a feedline loss of 4 db and a TV set noise figure in the 7 db range. The antenna height is 20' if you have a one story house and 30' for a two story house. A Channelmaster 4228 has a gain of 14 db, a preamp eliminates the downlead loss, and has a noise figure of about 3 db. So you can do about 12 db better than the prediction at the heights calculated. In many cases that is sufficient to receive DTV where only analog reception is predicted.

The TV stations in Washington, DC have a tower height problem because the city does not allow tall broadcast towers. This means that DTV in DC won't go as far as DTV in Texas.