I’ve taken an interest in LightSquared recently.
Today InfoWorld reports that the FCC “won’t allow LightSquared’s proposed mobile broadband service to interfere with GPS signals, even though the potential interference would be caused by GPS receivers picking up signals outside of their designated spectrum”.
So, the devices are in error, but the FCC is going to prevent LightSquared from interfering?
Sounds like the FCC should be going after the receiver manufacturers to ensure their systems don’t bleed over, rather than after a company not operating on GPS spectrum.
Wait, I forgot: that’d be too logical for a government agency 😐
That article is very misleading. For one, when it says “A typical guard band between spectrum users is about 2MHz.” it fails to say under what conditions. Guard bands very across the radio spectrum and depending upon the signal being transmitted. At 146 Mhz, for example, allocations are normally spaced with 0.015 Mhz between them to accomodate how wide the normal signals are there. As you get higher in the spectrum, signals tend to take up more bandwidth on either side of the specified frequency. The fact that they take up more space than the specified frequency is true of all radio signals. The lightsquared signal is described as being “broadband”. As a radio person, to me that says it’s signal is very wide and at that high of a specified frequency it isn’t surprising to me that it would exceed a 2Mhz guard band, especially if it’s using a spread spectrum modulation. The 23 Mhz guard is simply meant to make sure that the signals that lightsquared is transmitting don’t extend into the GPS frequency range.
BTW, while the political arm of the FCC does things I think are fairly questionable, it’s technical arm is top notch and has a long history of technical excellence.