I tried this in two vehicles. The first was a Toyota Sequoia with power antenna and the addition of this HD module rendered the power antenna inoperable. After checking all wiring and trying the head unit stock and with this HD receiver it was definitely something with the HD receiver. I called Kenwood support and they got back to me real quick (kudos there). However, they had not heard of this problem and couldn't help me but make some guesses about grounding through antenna sheath. Nice try but nope. One thing the technician did suggest was installing an antenna power amplifier to get good signal strength; like he knew something was up with the unit. So I boxed it.
I broke it out again when installing a second Kenwood system in a Ford Super Duty without power antenna just to see how it worked. Dismal at best. Again an antenna amp may help but then I discovered there are hardly any HD channels in my area anyway. And the automatic switching between HD and SD is annoying.
The whole HD radio thing seems preposterous. It's an apparent attempt to compete with satellite radio but cannot compare. I also see no improvement in sound quality due to the extreme compression that HD radio does in order to get signals to fit within frequency band. Me thinks HD radio will go the way of Beta tapes and Toshiba HD DVDs. There may well be a reason you don't see many head-units manufactures jumping on the band wagon with enthusiasm. I should have done more research before trying it.
I guess I'll put mine up on eBay and happily drive around with good, solid, strong and dependable standard-def radio.
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