It's natural to suppose that transmitter, antenna and grounding experiments sometimes require "pushing the limits" a little bit. This is not so, as it is quite possible to miniaturize range experiments for perfectly useful results safely within part 15 limits.
As the author I grant myself permission to reprint this from another forum.
It is possible to conduct transmitter/antenna performance tests without ever exceeding part 15 field strength limits and I'll tell you how I do it.
By setting a transmitter ouput power several times LOWER than permitted by part 15 the test range becomes miniaturized which is convenient because it will confine it within the house or yard and not require any driving around. With such a low power every change made to an antenna can be measured easily and when one antenna is better than another you'll find it out within a few feet instead of up to a mile.
Because it is possible to conduct experiments WITHIN part 15 limits, there is no reason to exceed field strength limits for experiments. The FCC knows this, and therefore will not accept "experimentation" as a reason for transmitting illegal power.