There's no reason a battery powered jammer won't fit in a bouy or "mine" or drone. If you're already declared an area a "no fly zone" or "no float zone" then j

There's no reason a battery powered jammer won't fit in a bouy or "mine" or drone. If you're already declared an area a "no fly zone" or "no float zone" then jamming civilians is not going to be a serious concern. We're coming to the end of a golden era where RF electronic reasons used to mean significant jamming was somewhat unrealistic at an analog electronics level. In the "next big war" jamming is going to be cheap and ubiquitous on the battlefield (or for that matter, in terror attacks or whatever). There is an interesting economic warfare aspect where a jammer drone is inherently always going to be cheaper than the antiaircraft missile or antiaircraft drone that shoots it down due to certain precision flying and targeting requirements. A jammer has to keep the right side up and not hit anything, and anti-jammer has a much more complicated task of finding, reaching, and destroying a jammer. So it being cheaper to jam than to unjam means only the wealthiest aggressors with good logistics support will be able to decide when GPS will be usable on a battlefield. Also unjaming has certain risks... sure go ahead shoot down that jammer drone, the site that launches a missile or even a drone will get plastered about one minute later by what amounts to counterbattery artillery fire. Now you have GPS data but no anti-aircraft cover... hmm, probably not a good trade. This is before meta level games are played where you want to lure someone into an ambush by jamming the heck out of everything but one heavily armed and prepared "empty" mountain pass. In the future I think you can pretty much count on GPS not being available or at least not being reliable on the battlefield, and when the enemy does let you use GPS they're probably messing with you. The concept of drones being cheaper than what it takes to shoot them down has a meta problem first discussed in anti-star-wars technology in the 80s where MIRV ICBMs had decoys... You can expect X drones of which only Y contain expensive jammer hardware, making the cost ratio of anti-jammer drones even worse compared to jammer and decoy drones.