Those loop antennas were marketed under the name "Boatenna", and if memory serves, you had to put it together. Not much more work to roll your own, IMO. You do have to use 300 ohm twin-lead, though, or a Balun transformer to convert to 75 ohm coax.
The problem with them, I would think, is that most digital TV is now in the UHF band, making the hoop much too big for the shorter wavelengths of UHF, though if the signal is strong, it won't matter. In my area, there are a couple of stations still in the high VHF band (10 and 13), but most are UHF (including 8, and the rest being 21 and higher).
A cheap UHF bowtie from Radio Shack (fan dipole) works very well, though it's directional. I've also used a cheapo set-top rabbit ears unit with UHF hoop on the deck. Worked very well, but I wasn't very far from the transmitters.
In case the marketing folks have you convinced otherwise, 'digital ready' and all that hype is just that - hype. The signals are still UHF and sometimes VHF, so conventional UHF and VHF antennas will work just fine.
If you're curious as to what the broadcast frequencies are for the stations you want to receive, go to
http://www.antennaweb.org/aw/welcome.aspx , hit 'choose an antenna', put in your zip code, and it'll give broadcast channel, tv channel it maps to (usually not the same since the changeover), distance and direction to the transmitters, etc. Very informative.
