Good question. If a leapfrog simply tunes a broadcast channel, filters it, and heterodyne converts it to a higher frequency for rebroadcast, it just might work with a digital channel, since the filtering in such a device would be primitive and unlikely to damage the digital waveform, but I've never tried it. I haven't seen any consumer device actually marketed as a digital, single channel repeater yet.
I think the "X factor" in this would be frequency stability and lock. Analog tuners have "capture ranges" that allow them to lock onto any signal within a couple of MHz of the selected one, and they look for the visual carrier. If a consumer repeater has AFC on its input but doesn't find a visual carrier, it might not end its scan of that frequency range right on the nose as far as the tuned frequency is concerned, or it might react to a failure to lock by rescanning every so many seconds. Twenty five years ago, when cable TV boxes and TV tuners were even more primitive than they are now, I did business with a sportsbar that used Jerrold Starcom 7 cable boxes and Sony TVs. The Starcoms would put out a channel 3 that was a MHz or two low, and while the Sony TV would briefly settle on it, about once every fifteen seconds, it would rescan that range, probably looking for a better frequency match.
The other prospective problem is that if the leapfrog receiver output is not sufficiently precise, it might not be precise enough for the tuner in a digital TV, because I don't think that the digital TV tuners have anywhere near the "capture range" of the analog TV tuners. If I set an analog TV to "cable" and connect it to a broadcast TV antenna, it will find UHF 26 and call it Cable 77, and will call UHF 32, Cable 83, even though they are each two MHz off-frequency, but no TVs I have tested will lock onto a digital UHF broadcast frequency channel when the input channel plan of Cable TV has been selected, even if its tuner is capable of processing 8VSB when found on Cable TV frequency channels, as the current LG sets can. In other words, if I set an LG TV on cable in and connect it to a broadcast antenna and scan it, it will find no channels, but if I electronically shift one or more of the broadcast channels by 2 MHz to a cable channel, the LG will find it AND demodulate it, even though it is 8VSB rather than QAM, but most consumer TVs won't even do that.
At this point, we need to have someone with a leapfrog try it in this application.
