Here's an interesting idea. Because DBS satellites are parked over the equator, DBS home dishes all point to the south. So if you had terrestrial transmitters pointing south, with receive dishes pointing north, you could use the same frequencies.
In fact, you could use the same set-top boxes for both DBS and this terrestrial service, and merely add a second antenna and switch between the two antennas. That's the concept that Northpoint Technologies is pushing. Trouble is, the idea is totally and fatally flawed, and nothing more than a grab for spectrum.
Northpoint, which is backed by several Republican Party bigwigs, has been gathering political support by pitching the idea that its wireless video service could be used to carry local television channels, complementing the DBS pay television service. Congress is under extreme pressure from constituents who face the cutoff of broadcast channels from their DBS service, because of copyright lawsuits brought by the TV networks. So key Congressmen are pressing the FCC to allow this Northpoint service to be used to deliver local TV channels, as an adjunct to DBS.
However, DBS operators don't want to partner with Northpoint. First, there are substantial interference issues. Second, Northpoint wants to use the whole 500 MHz of spectrum allocated to DBS, which is far more than is needed to carry a few local broadcast stations. In fact, Northpoint could carry enough channels to be a full-blown competitor to DBS.Interference
The Northpoint concept is too simplistic. DBS dishes don't point directly south. Depending on whether they point at DirecTV or at one of the Echostar satellites, they might be pointing southwest or southeast. So depending on the pointing directions and the locations of the dishes and the Northpoint transmitters, Northpoint signals might be leaking into the sidelobes of the DBS antennas and causing interference. In addition, Northpoint signals could reflect off of buildings that are south of the DBS dish and enter the dish directly.
Northpoint got an experimental license from the FCC to do some tests in Austin, Texas last December. The test report that was submitted to the FCC reads like a college electrical engineering lab book. They didn't calibrate the test equipment. The transmitter log says the transmitter was turned off at certain times, but there was signal data recorded at receive sites at those times. There were discrepancies in recording site locations. The test receiver system was installed in a bucket truck and driven from site to site, but this meant that receive sites were generally at curbside rather than typical DBS receiver locations. And most important, they didn't measure the bit error rate of the DBS signals, but instead used the uncalibrated signal strength meter that is built into DirecTV and Echostar set-top boxes as a surrogate for bit error rate. Northpoint claimed that there was no interference, no user-detectable degradation in DBS video caused by the Northpoint transmissions. But DirecTV looked at the data and said that the Northpoint signal caused unacceptable interference levels over more than 50 percent of the Northpoint service area. It turns out that there are international standards for evaluating interference to DBS in bands that are shared with other services. The real interference problems show up on rainy days, when the satellite signal is attenuated. Austin doesn't have a lot of rainy days. It isn't sufficient to merely look at the pictures and try to find interference artifacts. But Northpoint evidently didn't know that, or ignored it.Compatibility
Northpoint's idea of hooking up two dish antennas to a DBS set-top box, and switching between them, is too simplistic. Keep in mind that DirecTV, Echostar and the broadcast/cable digital video standards are all slightly different. Echostar and the U.S. broadcast/cable industries use MPEG transport packets of 188 bytes, while DirecTV uses 132-byte packets. The program guide and system information protocols are different. Northpoint might be able to buy off-the-shelf encoders and transmitters that conform to the broadcast/cable version of MPEG digital video transmission, but the DirecTV and Echostar versions are proprietary and incompatible. Northpoint could not easily purchase compatible transmitters, not without the prior agreement of DirecTV and Echostar. And they don't have any interest in giving that agreement.
Although Northpoint has pitched this service as a complement to DBS, it's clear that the real plan is to grab this spectrum, without having to bid in an auction, and then use it to compete with cable and DBS. Never mind that the FCC created the LMDS service for exactly this purpose, and required interested parties to compete in an auction for LMDS frequencies. Never mind that in the vicinity of every Northpoint transmitter, there would be interference to DBS home dishes.
I don't think they will succeed, but you never know. With the FCC getting beat up by Congress over the absence of competition in the telephone business, maybe the FCC will give in to Northpoint's friends in Congress.