Hi jhunt17, Wid and JohnK,
I just spoke to Tom Cumberland Axiom's senior design engineer, and he pointed out that TV-cable systems supplying digital HD signals combined with many other services use a combination of phase manipulation and multiplexing to cram all the services into a minimal bandwidth in order to pass all the stuff through the copper cable.
Using a pair of 75-to-300 ohm balun-transformers worked in the days of analog TV, but according to Tom, transformer-based ground islolators will do "nasty things" to the phase and multiplexing, which explains why you are not getting your HD digital signals.
It's early at this point, but he says a capacitor-based isolation device should, in theory, be OK. Axiom is getting in some prototypes that we'll take apart and test with digital HD signals and eventually offer one that will effectively pass a digital cable TV feed with no degradation while still doing its job of isolating the cable ground and eliminating ground loops caused by the cable feed.
I suspect the cable line isolator sold by Parts Express may be transformer-based, which may explain why it's mucking up the HD signals.
Stay tuned.
Regards,
