Although it's true at this time cable companies are required to provide local HD in clear QAM, which the SiliconDust is compatible with, the FCC is currently considering a proposal to allow cable systems that are all digital to encrypt all channels including local HD channels.
If the FCC approves this request, which it appears they will, the SiliconDust will soon be useless for cable, as most all cable companies are in the process of converting their systems to all digital. Comcast for example, the largest US cable provider, has already converted over 20% of their systems to all digital. There will most likely be some exceptions to this, but expect to see most cable systems go all digital to take advantage of the upcoming FCC ruling.
Regardless of that, the SiliconDust is fully compatible with over-the-air Digital TV reception, as long as you have an antenna and are roughly 60 miles or less from the broadcast stations you want to view. Local broadcast stations typically include ABC, CBS, FOX, NBC, PBS, and in larger metropolitan areas also The CW, My Network TV, ION, TeleFutura, Telemundo, Univision, and other local independent stations.
Viewing local stations using over-the-air Digital TV has a few benefits over viewing the same stations using clear QAM from cable:
1) After you buy the hardware, it's totally free.
2) The HD quality you get over-the-air is as good as it gets. Many cable systems additionally compress local HD on their systems, but when you use an antenna, it comes direct from the source.
3) If the cable system has technical issues with local stations, you are out of luck. When you use an antenna for over-the-air, unless a station goes entirely off the air, you will still be able to view it.
To learn more about what stations you can receive over-the-air locally, go to TV Fool.com and punch in your info, and then post the results in the HDTV Technical Forum at AVS Forums. You'll get lots of advice about what antennas to try and how to optimize reception.
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