If you think you're going to sit on the ground with even my 18kj maxwell cap bank (the kind of thing we invaded iraq around - and that will make a 50ft ball of plasma out of 1/2" copper conductors shorting it) and burn the front end out of the radios in a drone 30k feet up, without some pretty hard work, you're dreaming.
This is how it's done these days:
http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator
The cap only provides the initial magnetic field for an explosive-driven generator that puts out the real juice. By choosing the output device and antenna appropriately, you can pick what you burn out. You can tune things to the little slots in the back of a PC act like slot antennas and just burn out PC's. Or cell towers, or...power lines (all at different output frequencies). But, square law attenuation if you don't have a *directional antenna* which the better it is, the harder it is to aim right - and the bigger it is. Therefore, it will show up in sat pix.
Believe me,
every major intelligence agency would be knocking on your door very shortly after making a spike like that. All of them, and not just ones from this country. There's a constellation of birds, "assets", constantly looking for just that kind of thing (partly because other things of interest also make such spikes). Even if the state of the current art is as retarded as it was when I myself designed such assets for a living.
I think the record jamming time, when someone took over a satellite feed to put porn on a christian station feed, lasted all of 30 min before they shut him down - physically, and in person. In other words, he was located in a fraction of a second, and that was the drive-time to his place for the feds. If you want to knock down drones, you'd better look for something that they can't see coming. Or more importantly, tell where it came from.
One precise projectile with passive aiming...a computer handling all the trajectory variables (wind, spin drift, Coriolis effect, lead etc). Chey tac makes something like that, but not good enough for this. Theirs won't handle moving targets.
But you still have the issue - if drones start falling out of the sky in an area, someone's going to be very interested in who can do that, why they are doing it, and they'll put a stop to it quick. Even I out in the boonies couldn't escape that level of scrutiny. Best just to stay under the radar - or work against the drone base itself.
Why do you think the people we currently use them against hate them so much? There's almost no effective countermeasure.