I just read through the LightSquared story and am pretty intrigued!<p>One of the fascinating demonstrations of the fact that GPS is relatively interference robust is that Galileo (ESA GNSS system) runs on the same frequencies as GPS; the different spreading codes mean that receivers can choose which signal to listen to.<p>Reading about the LightSquared system though, they do talk about a quite real concern: overloading the receiver&#x27;s frontend entirely. That&#x27;s one of the concerns that would be addressed by using directional antennas (if you&#x27;re receiving interference, rotate your antenna so that the source is in an antenna null). As far as I know, most civilian receivers wouldn&#x27;t have a directional antenna, they&#x27;d have an omni so that they work in any orientation; it&#x27;d suck if your iPhone could only receive GPS signals if it were sitting flat. On a military vessel, it&#x27;d make a lot more sense to mount an upward-cone-looking antenna high up on a mast to avoid sources of surface interference.<p>I&#x27;m super curious now though! I&#x27;ve got a software GPS receiver set up, I&#x27;d like to try injecting noise into the (virtual) signal chain and see how much noise power is necessary to lose lock. If anyone&#x27;s curious, GNSS-SDR works great with $20 RTLSDR radios: <a href="http:&#x2F;&#x2F;gnss-sdr.org&#x2F;source-code" rel="nofollow">http:&#x2F;&#x2F;gnss-sdr.org&#x2F;source-code</a><p>Edit: I did a bit more research, and it sounds like overloading the front-end is the most common approach to jamming. People are turning on multi-watt transmitters in their vehicles (e.g. to block fleet management GPS from detecting their location). Despite the amount of power they&#x27;re putting out, they seem to be limited in range to around 50 feet.<p>It&#x27;s also pretty satisfying to see <a href="http:&#x2F;&#x2F;www.novatel.com&#x2F;assets&#x2F;gajt&#x2F;pdf&#x2F;gajt-white-paper.pdf" rel="nofollow">http:&#x2F;&#x2F;www.novatel.com&#x2F;assets&#x2F;gajt&#x2F;pdf&#x2F;gajt-white-paper.pdf</a> which indicates that the solution I came up with (directional antennas with nulls pointed at the interference sources) is a solid strategy for mitigating jamming.