EMPs fall off with the square of the distance, there’s a reason the only ones with any kind of regional effect we’ve been able to produce were through the use of nuclear weapons. Even in the event that you had some non-nuclear means to produce them the cost of hardening your own equipment and producing the EMP would be way higher than the cost of the drones, and you’d also be putting a very high value target on the field to be taken out by artillery.