The paper covers the use of a COMB generator to detect and diagnose RF problems related to cable and shielding problems in data acquisition systems in situ. The setup and method to conduct these tests is discussed in detail. Circuit design for a COMB generator is covered, as well as commercially available units. The use of a spectrum analyzer for the detector is covered and characteristic outputs are examined. Low cost alternatives to the spectrum analyzer are also examined. The COMB generator and the spectrum analyzer used for the test are portable devices and so, lend themselves to field use where access to alternating current sources is problematic.