There is NO 1080P over-the-air broadcasting: you have either 720p or 1080i broadcasting: the differences between the two are not really significant, and your grandmother is unlikely to see any difference at all. The choice of 720p or 1080i is made by the broadcaster, and isn't a user choice. Choose on the basis of needs and price. LCDs work better in brightly lit rooms, plasmas have more natural on-screen motion and a more film-like presentation. When choosing a TV for your grandmother, pick the biggest quality TV set that you can afford that won't give her a headache, and find a set that eschews gimmick features, but provides the best combination of picture quality and ease of use. Many manufacturers charge heavily for features like picture-in-picture, and gamer oriented features that she won't ever use.

If all the transmitter sites are within a 40 degree arc, then directional is your best choice, and will provide slightly better signal strength. While an omni-directional antenna would receive them as well, it could pose problems in areas with foothill mountains or tall city buildings behind the antenna. That is what is traditionally is known as multi-path distortion or ghosts in analog broadcasts. The transmitted signal is reflected from behind and slightly delayed when it reaches the antenna. While digital broadcasts are more capable of dealing with this, they are not immune from problems. As far as a metal roof, as long as your antenna is above the roof line, there should not be any issues. Which just occurred to me, if you were considering an attic mount, a metal roof makes this a no-go. Also make sure your ground the coax, through a coax grounding block, to eliminate static buildup which can cause "sparklies" in the picture or can occasionally, if the static build-up is bad enough, even cause tuner failure. The mast itself should also be earth grounded for lightning protection - 10 gauge wire or larger.

I too have OTA (Over The Air) channels. I have a roof antenna. Although, it is sitting in my living room at the moment. I really need to find someone to install it on the roof. Anyhow, in Houston, there are almost 90 OTA channels. My antenna that sits in the living room picks up around 75 of them. Half are foreign & religious channels though. What many people don't realize is that with a TV antenna, we can actually pick up true high definition picture. Whereas, cables & satellite services often compress the pictures and what you see on your TV is only what you get from these services. Regardless that you have an HDTV (high definition TV). Anytime someone comes over my home, they're surprise of how crispy clear my TV is. All it is is simply true high definition signal via OTA. Between AntennaTV, MeTV and ION channels, they keep me entertain 24/7. I'm not a big sport fan; thus, paying to watch TV just doesn't make sense to me. I had Infinity and Uverse young salesmen tried to sell me their services. They insisted that their service beat the price of all the others. I repeatedly tell them: No thanks. Then, they asked me: "What do you do for TV?". I simply point my finger up in the air and tell them I watch OTA channels. They had this puzzled look. LOL, these kids had no idea what OTA channels and a roof antenna were. After getting some lengthy explanation, they admitted that they can't beat the price of OTA channels. LOL... these kids...

Ability to receive OTA (Over-The-Air) broadcasts is based on things in addition to distance. I live about 60 miles E of NYC, and can receive most, but not all broadcast channels from there (I even sometimes get reception from a station in NJ!). In most areas now, there are no longer any low-band VHF stations (channels 2-6), but many UHF stations. So I got a high-band VHF antenna and a UHF antenna and mounted them on a 20 foot mast. I also got the best preamp I could find for under $200. I put this assembly on my west-facing deck and ran an RG6 cable into the house where the other half of the preamp and the TV are located. This setup works pretty well, although sometimes the sound drops out, but I can live with that. I intended to move this to the roof, but that's 40 feet off the ground and I'm scared to climb up there! (Remember, that after the digital conversion of broadcast stations, most changed their frequencies. In the NYC area, all the high-band stations stayed where they were, but the low band ones, including CBS, NBC, and Fox, all changed their broadcast frequencies to ones in the UHF band, but kept their old channel numbers in their logos. Modern digital TVs will search for all stations and display the old station numbers, even though they are using the new ones).