Hi - welcome from Medford MA.
You pretty much have two markets you can aim at, Providence and Boston. The main advantage to aiming for Boston, IMO, is that you get all the major networks on UHF. If you aim at Providence WNAC 12 and WPRI 13 are VHF-high and will require an antenna that covers both UHF and VHF high. Or, you can try and get a mix from both markets...
There are lots of antennas on the market with differing claims... but siting is really important. First, I would say if you are willing to put the antenna outside, you will be way, way ahead of any indoor mounting. From your outside location, higher is generally better, and you want to pick a location where the line-of-sight (LOS) to the transmitter is clear to the horizon. No obstructing trees or buildings.
Are there any stations on your list that you particularly want to get? If it were for me, I would want WGBH/WGBX from Boston.
I have an Antennas Direct DB8e on my roof (UHF only), along with an Antennacraft Y10713 for VHF-high. The DB8e has two panels that can point in two directions, so you could try and split it between Boston and Providence. Then if Boston is not reliable, give up on Providence and point both panels at Boston.
You can also add a VHF-high antenna to the same mast, like the Antennacraft Y5713, point it at Providence and pick up 12, 13 and maybe WWDP 10. You can mix the UHF signals and VHF high signals with a UVSJ or a mast-mounted preamp.
https://www.antennasdirect.com/store...V-Antenna.html
http://www.antennacraft.net/Antennas/AntennasVHF.html
http://www.solidsignal.com/pview.asp?p=uvsj
http://www.amazon.com/RCA-TVPRAMP1R-.../dp/B003P92D9Y
Or, you could point at Providence with a combination antenna like the Antennacraft HBU-44 and skip the Boston stations. Similar antennas from Winegard, Channelmaster and likely others are available. Expect a detailed spec sheet with performance numbers in dB for any of these antennas, not just claims.
But first, I suggest you look at your site to see how you can best mount the antenna. There are lots of ways to erect a mast, and you will need to ground it properly and bring the cable in from the mast. If you try and use existing cables, and you get nothing, suspect the cables. New cables are cheap, relatively speaking.
hth!