GPS is a very low amplitude signal that can easily be jammed. Dropping WP (white phosphorus) or a missile on the suspected jammer would be a better bet.
"Your GPS jammer prevented my war crime so here's a bigger war crime." - The good guys
The antenna would[1], but the valuable electronics has no reason to be left outside, and practically any amount of concrete, rock or even dirt would protect it from WP.
Also, from your description you're probably confusing WP with termite, which is different (but would be equally inefficient again EW devices for the same reason).
[1]: and with WP you're likely going to just damage the wires and not the antenna itself
At least with HE you can limit the damage to the particular place that holds the device, when I'm not familiar with any use of white phosphorus through precision munition (I'm far from a munition expert though, so I may be wrong here).