My minimum recommendation would be the Antennacraft HBU-33 in the attic. I am assuming the garage doesn't have aluminum siding? Unfortunately attic reception is very unpredictable & may require trying many different locations around the attic to find a good spot where all of the desired channels are reliable. If mounted outside in the clear, something as small as a Clearstream c-2V or RCA ANT 751 would do the trick.
I recently put an RCA ANT 751 at a friends restaurant across from Westgate shopping center in Manassas. The
TV FOOL report is a bit worse than your friends, but reception is near perfect. An occasional glitch due to low aircraft approaching Dulles airport seems to be the culprit. We spent about 1 hour trying different spots above the drop ceiling before finding a sweet spot.