Um...

This site:

https://maritime.org/tech/radionames.php

Has this paragraph:

"On the second contract for a specific model, the model designator was suffixed with "-1" (a second contract for the RAK would be designated as "RAK-1", a third contract as "RAK-2", etc.). Authorized modifications of the system by the Navy after delivery would result in addition of a lower-case letter suffix (such as RAK-1a, RAK-1b, etc.). Experimental equipment was assigned model letters beginning with "X" if manufactured by the Navy (XA, XB, etc.), or with "CX" if commercially manufactured (CXA, CXB, CXAA, CXAB, etc.). Preliminary models of equipments, intended to become the property of the Navy under the terms of a contract, were given an "X" prefix letter, separated from the basic designation by a dash. The preliminary (test) model of "Model TBU" was therefore designated "Model X-TBU"."

CX means it was commercially designed, and experimental. AB apparently was where in the series this set was adopted (i.e. "after experimental set AA"...)


Beyond this, I can find nothing specific about that particular item. That it required an antenna is evident from your own material...the 7/8" transmission line for it was shorted.

For the TCD/RAR, my searches yielded nothing. However, if any of the above link's abbreviations are applicable, then it looks like "transmitter model CD with receiver model AR." ???

Best I can do.