A view of the tube enclosure as seen from the back of the enclosure.  Notice the aluminum tape covering the seams in the case. The tape is used to assist in preventing RF energy from escaping through the seams in the case.  The screws used to fasten the case together may be seen under the tape. In the lower center of the case is the metal plate which holds the SO-239 RF coaxial connector by which RF power enters the enclosure.