Absolutely no "HDTV" antennae is required IF the one you have provides a clear image! My wives parents received a new HDTV as a present from their two daughters. They do have Dish, as they live at least 20 miles from any TV station, but they also use an antennae that must be at least 20 years old! That antennae picks up analog stations from well over 70 miles away. I was absolutely amazed at the high quality images they get now, from the old 'analog' antennae! Frankly, it's much better than what we get via cable on our analog sets!
The only reason I would suggest a new antennae would be if you are using one that is not bringing you a very clear picture now. But even that may be corrected by aiming it better, raising its height or avoiding signals bouncing off of buildings in your area. If your rabbit eras are giving you a fine picture, use them! You'll still need a box, of course, to get the digital image converted to an analog signal that you can watch on the analog TVs.
Another bit of info that may end up causing people to complain, especially those near the out limits of a stations coverage area, is that digital is exactly that, it's either a 1 or a 0, it's either ON or OFF. You should never get a weak/snowy picture with the digital signal. You will get either a beautiful image or a black screen perhaps showing that the signal is too weak.
