Drill hole in bottom skin for transponder antenna

The transponder antenna is driven from an unbalanced coax, connected via a BNC connector. The shield of this connector makes proper contact with the skin on its interior surface. On the other hand this antenna is a 1/4 wave so relies on a ground plane intimately connected to this shield. As the connection path must be a small fraction of a wavelength (30cm at 1GHz) in order to not affect the operation of the antenna, the antenna must be mounted on the outermost skin layer, and via any doublers. Fortunately, in this case the skin is 0.63mm, not too thin, so no doubler is likely needed. If I were to introduce a doubler I will make the doubler it would be an exterior doubler, and be the mounting surface of the antenna.