You're leaving out a major stipulation of the FCC's ruling: whitespace devices must listen before transmitting, not just query the database.
You're right, but I was trying not to complicate the argument. Consider the situation, though: The farmer needs a tall tower (30m is not unusual), a high-gain (10-15 dB), directional antenna, plus a low-noise, high-gain mast-mounted preamplifier to watch his television. What are the odds that the sensing system associated with a secondary user also will be able to detect the television station? (Hint: Substantially zero, since it is not economically feasible to sell the associated tower with every secondary use product, even if it could constantly rotate its directional antenna.) The television user's receiving system is far more sensitive than a secondary user's sensing system could possibly be.
If the above weren't bad enough, add in the fact that the co-channel rejection ratio of ATSC digital television is specified at 15.5 dB desired/undesired, meaning that any co-channel interference must be at least 15.5 dB weaker than the desired ATSC signal if the television signal is to be received correctly. This requires the secondary user to be able to detect (but not necessarily decode) the ATSC signal at a level 15.5 dB below that of the television receiving system. These two requirements almost guarantee that there will be unhappy rural television viewers.
There's plenty of truly empty spectrum to use first.
Keep in mind that the spectrum database defines empty spectrum, as far as the secondary user is concerned. He send in a request, and gets a go / no go reply. He has no idea whether the requested spectrum is "truly empty" or not. And if you examine television channel occupancy in the US, I think you'll find that all available channels are occupied by television stations, since they were incredibly profitable for many decades. Considering fringe signals, not just licensed coverage areas, every channel is either occupied, or its adjacent or image channel is occupied. The White Space concept counts on using these fringe areas -- that's the whole idea.
More likely, considering said whitespace device is probably providing him Internet service, he'll turn the TV off and get his TV program through his Internet-providing whitespace device
How many people watching "American Idol" on their home television systems, for which they've paid thousands of dollars (towers, antennas, and large screens aren't cheap), are going to say, "yeah, you're right -- I should just forget that and buy that new White Space Internet service instead"? Especially when they're likely to learn of the Internet service from their TV repairman, called out to fix the interference problem that suddenly started on the first of the month? What if the situation were reversed, and someone took your Internet connection away and, when you complained, told you to watch television, instead? I'm betting you'd be just as ticked.
Re: the wireless mics, you're missing the point. In ENG, they're largely used by the talent to do voice-overs, usually live. The problem isn't whether they're going to cause interference (they're already licensed for operation on television channels, and have been for years), the problem is how to protect them from interference caused by new White Space devices. (Which you want to do: I don't know a faster way to kill a new technology than to turn the media against it.)
When one actually does the engineering of the system, it turns out to be substantially impossible to detect wireless mics at levels required to provide them protection: The transmitting antennas are low (often worn on the belt) and not very efficient, and the transmit power is low, while the receiving antennas are often placed high on the ENG truck's mast, and the receivers are relatively sensitive. A secondary device will almost certainly cause interference to the mic receiver long before it would be able to detect the presence of the mic transmitting. For a live news feed, this is a real problem -- so much so that the IEEE 802.22 Working Group on Wireless Regional Area Networks ("WRANs") felt it necessary to establish Task Group 22.1, "to enhance harmful interference protection for low power licensed devices operating in TV Broadcast Bands."
The selected method was to standardize a beacon that would be placed near the wireless mic receiving antenna, and would transmit in the White Space bands whenever the wireless mic was in use. You can imagine all the requirements that must be placed on such a system to make it practical: How the beacon itself keeps from causing harmful interference to other microphones; how to handle large groups of mics, like the hundreds of co-located mics at political conventions, without requiring hundreds of co-located beacons; how to design the beacon so it can be detected quickly while at maximum range (i.e., while it's weak), and in the presence of multipath propagation and other channel impairments; how to make it authenticatable, so that White Space users can be confident that they are protecting a legitimate user, and not some unethical business competitor or script kiddie; the list is endless.
To sum up, I guess I have two points:
1. Don't ignore those you displace or disrupt with a new technology, for they, too, have political representatives; and
2. Don't underestimate the technical difficulty of White Space use. Keep in mind that an existence proof -- a functioning system in the field -- has never been satisfactorily demonstrated.
