I'm just curious as to why this add on tuner is as big as the HR21 when the HR20 has the ATSC tuners built in ( I can't remember if the HR20 has two or one tuner).
The HR20 has two tuners.
As for why?
Sizing on a rack/av components.
It being the same size, it just blends visually better...
And allows a lighter component to still be stacked on top of it (like a DVD player or something of that nature)
Or to easily be mounted in a rack as it is not larger then 1U... with some of the same type of mounting equipment out there for the existing products.