I bought one of those Chinese GPS jammers, mostly just to see how it worked. I had no intention of actually jamming anyone's GPS. When I turned it on, my Z3801 GPSDO immediately went into holdover. I turned it off. Later, I went to the car, let my Garmin GPS get a fix and turned the jammer on. Nothing. The GPS just kept right on working, even with the jammer antenna touching the case. Turned it off, and never turned it on again. It was just a canned VCO, and a 555 producing a sawtooth wave to sweep the frequencies around where the GPS signal is. I am no expert on these jammers, but most are just very simple sweepers. A while back, people using bluetooth earbuds to talk on their cellphones became almost an epidemic at my local Wal Mart. It bugged me no end to see all those people walking around carrying on a conversation with no one around. I actually looked into what it would take to build a bluetooth jammer. Because the earbuds are so close to the phone, it would take a fair amount of power to jam them from a distance. The project ended right there. I don't notice people using those all that much anymore. I did see one lady carrying on a very heated discussion as she shopped. After a while, I noticed that she wasn't wearing earbuds at all, and didn't even have a cellphone. You see all kinds at a Wal Mart.
