The DTV tech came over yesterday and installed the new dish and on finishing up, showed me the BBC converter. " Should be attached!", he says and leaves..
So it was apparently out of his realm to move the TV and install it...

Since there's only one BBC with the H20 receiver, it would infer that there's only one place to install it, ie on the input from the dish....
However, I have two input cables, one says from satellite dish, the other "external antenna"
Do I need to attach one of these converters to BOTH inputs, or just on the line that says "satellite dish".
I realize that both inputs are coming from the splitter below the dish, so in effect they are both coming from the dish.
So, did I just answer my own question?
thx

Rjonst - maybe you did but you raised another one!!
Yes, the bbc just goes on the satellite input.
Your OTA cable should be coming directly from your OTA antenna, not connected to any sort of splitter at the dish. Did the installer put in a diplexer so you could run OTA and satellite down the same cable? If so this is WRONG, everything will work ok now but as soon as the new satellites DirecTV 10 and 11 start transmitting later this year things will go wrong in a big way.