Spark gap transmitters are kinda jank. They emit noise across the entire radio spectrum, interfere with everything, and will draw the ire of the FCC. Probably one of the few things they will actually look into if it becomes an ongoing problem. Spark gap transmitters are extremely inefficient. Only a very tiny fraction of the power will be converted into RF at the correct frequency to interfere with the target. They are very easy to make, however. Literally, build a circuit which makes sparks - mission accomplished. Just don't electrocute yourself. Turn on an AM radio in the middle of the thunderstorm sometime, and you can observe this phenomenon yourself (don't walk around outdoors with an antenna in an electrical storm like an idiot though).

A much more effective device would specifically target the frequencies in use, putting all of its power into that bandwidth instead of wasting it jamming airplanes, satellites, broadcasts, and cell phones as well. This can be enhanced with a directional antenna like a dish or a yagi to increase the gain (stronger signal with same wattage) and mitigate some collateral damage. This type of device should only be used momentarily (i.e. temporarily disabling a drone). Anything permanent will be detected and investigated, as well as anything temporary which is actually leading to drone kills.

Modern radio systems built using spread spectrum technology are much more resilient against jamming. I do not know enough radio stuff to really know a good way to counter them. Due to their military applications, there is definitely a lot of research going into constructing them and jamming them however. It surely will be a lot more work than desoldering a resistor from a yaesu, plugging in the frequency and CTCSS tone for the municipal cops' analog FM repeater, and sharing your favorite N.W.A. songs with them.

If the bad frequency is not known, It is possible to investigate spectrum usage in your area using something like a RTLSDR (a USB software defined radio receiver). A RTLSDR combined with a directional antenna can be used to pinpoint what direction which signals are coming from. Different chips may be needed to operate at different frequency ranges. An ordinary RTLSDR (originally based on USB VHF/UHF TV tuner cards) won't be able to operate on the 2.4ghz and 5.0ghz bands. There are other chips which can do this. With radio equipment in general, there is no one size fits all. Radios either handle one job well, or several jobs kind of shitty.

Every now and then, amateur radio operators set up "Foxhunting" events, where contestants use radio equipment to hunt down the location of a hidden transmitter. You can find a lot of useful information about the techniques employed to do this (and perhaps, how to counter them) by searching for ham literature about foxhunting.