Before the High-New series of Y-8 ELINTs, the PLAAF converted 5 Learjet (35A and 36A) into specialized ELINT spy planes. An attempt which was similar to the US EC-21 A program.
Since the 1980s, those birds of the PLAAF 102nd Independent Reconnaissance have performed ELINT missions ranging from Yannan (Vietnam), Fujian (Taiwan) and to HongKong (prior to the 1997 hand-over).
To see their current "Corporate Jet Register" (here)
Notice the "black box" under fuselage