I know someone that lives roughly 50 miles from a medium-large city, as well as about 70 miles from a couple of fairly large cities.
Are there indoor TV antennas she could use to get signals from that distance, or is that really not possible without a 30 foot outdoor antenna?
Amplifiers are useful when you have a long cable run from the antenna to the receiver, and/or are splitting the signal between multiple receivers. If you’re in the fringe or distant area from the broadcast transmitted (which it sounds like she is) then an amp likely won’t help. It’ll just amplify the noise it picks up along with the signal. In these conditions you want to worry more about the antenna design and directionality itself.
OP: to what extent are you surrounded by hills–which would block the signal?
Ask your neighbors and drive around (or perhaps there is a local electronics store you could ask at). I would guess they either have tall external antennas or use Dish/Directv.
It’s hard to give generic antenna advice because there are so many variables involved, not to mention surprisingly major variabilities in the antennas themselves, even those that look the same. That said, a few comments from experience.
I doubt that an indoor antenna will suffice for the kinds of distances you’re talking about (unless, maybe, your friend was living in a high-rise apartment that happened to be facing in the right direction and the stations were exceptionally powerful), and I concur with the previous comment about amplifiers. You may well need one for a mast-mounted antenna just because of the length of the cable run, but when I was originally playing around with my antenna indoors, I found that even the reputable low-noise high-gain Channel Master 7777 made no difference to the channels I did or did not receive – the TV merely reported higher signal strength, but it made no difference to receivability or stability.
Assuming that the stations involved are all UHF, the surest bet in that situation is a small outdoor-mounted UHF antenna. Channel Master has traditionally been well regarded in this area – I have the 4-bay CM 4224 myself, and there is also the more sensitive and directional 8-bay 4228 (these since appear to have been renamed ULTRAtenna 60 and EXTREMEtenna 80, respectively). There are other good brands, as well, but I would avoid the cheap no-names.
You might also consider the compromise of trying out an outdoor antenna indoors. The CM-type designs I mentioned are flat and the 4-bay is relatively small, so it can easily fit in an attic or even in a second-story window (if the direction is right) or outside-facing closet, but you have the challenge of running the cable. Height is critically important. And the all-important factor is terrain – the elevation of your immediate area, what is immediately in front of you, the intervening hills and valleys and land vs water. It’s very much a “try it and see” experiment, plus you can get good feedback as already suggested by talking to neighbors with antennas on their roofs who can tell you what works and what doesn’t and how reliable the reception is. Even just by looking, if you see (for instance) lots of 8-bay type antennas or other sensitive/directional antennas, you’ll know it’s a fringe-reception area for at least some channels.
I’ve done it once, with a highly directional amplified indoor antenna. It was made by Terk, but that’s all I can remember. It was 60 miles, roughly, from where I was to the towers in El Paso and it only worked because I had good line of sight due to the geography. I also had to place the antenna touching the exterior wall to get a stable signal.
I second that an amplifier is not nearly as important as height and direction (orientation).
My first step would be to ascertain if a directional antenna is appropriate. Are all the broadcast towers in the same general direction? If so, that’s very helpful in making your selection.
Second step, ask how high you can place the antenna. Can it go in an attic? Can it be placed outside on the eave or on a balcony/terrace?
As with all things electrical/electronic, the quality of the cable and the connectors is critical. Don’t cheap out on the feed cable from the antenna. On the other hand, do not buy a pre-terminated 50’ cable and then coil the unused portion somewhere.
I’ve seen flat, printed circuit antennae (like the Mohu Leaf) perform surprisingly well when positioned correctly, without any sort of amplifier at all. This explains the widely-varying reviews you see for some antennae.
Look at TV Fool to find out what stations are available (and how strong they come in). It is also important whether the stations you want are UHF or VHF. Then look at Antenna Web to research antennas.