Here is a revision for UHF (Only)...and perhaps very strong Hi-VHF channels that are going to come in no matter what:
I don't have just ONE answer to the question as to which is the "BEST" Indoor UHF Antenna....it all depends on your situation....and LOCATION.....
IF you have strong enough signals, a cheap NON-Amplified VHF-Rabbit-Ears+UHF-Loop (2 dBi or WORSE) may be all you need....and you might even get away with using one of those more expensive Flexible Antennas: Mohu, Flatwave (3-4 dBi), WallTenna (3.5-7.9 dBi w/o Enhancements, etc) or rigid Flat Panels (e.g. C-M, RCA, Terk, W-G, etc)....unfortunately we don't have SWR and Raw Gain curves for most of these. Note that I determined Optimum Dimensions to Enhance performance of the 2-Bay Bowtie WallTenna, which is transparent to place in a convenient WINDOW, where the signals are strongest:
http://imageevent.com/holl_ands/multibay/uhf2bays/hivhfuhf2baywalltennaenhancements
Unfortunately NON-Amplified
DIRECTIONAL Silver-Sensor UHF Antennas (to reduce Multipath) with VHF-Rabbit-Ears, such as Terk HDTVi (abt 7 dBi) and Philips equivalent appear to have been discontinued. This primarily leaves the Terk HDTVa (abt 7 dBi) which shouldn't be used with strong nearby FM and TV signals.
To obtain about 3 dB more Gain, you COULD mount one of the above Antennas in FRONT of a Reflector Screen (could be Aluminum Foil over Cardboard) that is AT LEAST 20% bigger than the Antenna (Bigger is probably Better). Separation should be about 5.5-inches...and it needs to be POINTED toward desired stations.
About the only NON-Amplified DIRECTIONAL Indoor Antennas with significantly more Gain than simple Rabbit-Ears (2 dBi or WORSE) is the Clearstream C1 (7.2-8.1 dBi).
If you need higher Gain in an Indoor location, consider "hiding" an OUTDOOR Antenna in a convenient Closet or Attic, such as Clearstream C2 (9.2-10.2 dBi) or for more Gain, any of the 4-Bay Bowtie Antennas....or even an expensive 8-Bay Bowtie Antennas. [I use a CM4228 8-Bay Bowtie hidden upstairs in a storage closet.]
http://imageevent.com/holl_ands/multibay/4bayrefl
Of course, if your stations aren't conveniently located in one general Direction, you many be FORCED to use one (or two) of the Bi-Directional Antennas mentioned above.
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In the ANTENNA SIMULATIONS link in my signature line, you'll find over 600 Antennas, mostly DIY Projects, that have been analyzed (and a BUNCH more on nikiml's website). The amount of Raw Gain increases as the size of the Antennas gets bigger and bigger....but for INDOOR use, I favor the 2-Bay, 4-Bay, and the extremely simple to build Hourglass-Loop and similar Quad-Trap. Although the UHF Hourglass-Loop provides significant Raw Gain, a simple UHF Loop may be all you need....and is significantly better than simple Rabbit-Ears with their compromised Impedance Matching Network....
A GOOD DIY Indoor Antenna for UHF (ONLY) could be a simple Project attaching a 300-75-ohm Transformer Balun to a 26.75-in piece of wire bent into a Circular Loop with OPTIMIZED 8.5-in Diameter (larger than usual Rabbit-Ears Loop)...or any of the higher Gain Twin-Loop (Figure-8), UHF Hourglass-Loop or Quad-Trap Antennas (et. al.) listed here:
http://imageevent.com/holl_ands/loops/uhfcircular
http://imageevent.com/holl_ands/loops
Note that versions are included above with Reflectors to increase Gain and also suppress Multipath & Interference coming in from the Rear.
Even better than any Loop Antenna is the newly Optimized H2+11RR, which is the current KING of the 2-Bay Bowties...only (barely) exceeded by the 2-Bay SOLID Triangle. Also note that H2+11RR was also "Best" for Hi-VHF with lower SWR (still Excessive, so not that impressive) and considerable Raw Gain
FORWARD (unlike OLD DB-2, Eagle Aspen 2-Bay...and other TOO SMALL commercial products):
http://imageevent.com/holl_ands/multibay/uhf2baysolidtrianglesvarrrs
[I didn't do a run without the Reflector Rods....should reduce Raw Gain by about 3 dB.]
For even more Gain, Dimensions for the OPTIMIZED FF4 or mclapp (sells a Kit) M4 4-Bay Antennas can be found here with & without Reflectors
[Listed in Order, BEST at Top]:
http://imageevent.com/holl_ands/multibay/4bay
http://imageevent.com/holl_ands/multibay/4bayrefl
Note that we also did a design exercise for the "BEST" Hi-VHF/UHF Antenna that could be HIDDEN behind a user's existing Picture mounted in a 3x2-ft METAL frame....where the METAL Frame HELPED Hi-VHF performance at the expense of UHF performance.....and MIGHT be somewhat skewed from optimal pointing angle, so check Azimuthal Patterns very carefully for any given situation. Alternatively, you could mount one of the UHF (Only) Antennas mentioned above inside (or sticking slightly out of) a NON-METALLIC Frame (e.g. wood or fibreglass):
http://imageevent.com/holl_ands/loops/hivhfuhfin3ftx2ftpictureframeloop