This question is in regard to the radiated immunity test specified in section 3.3 of GR-1089-CORE in which the test signal is 80% AM modulated with a 1KHz tone. In testing analog voiceband channels for idle channel noise per section 3.5.3(c) of GR-1089-CORE, we have been using a Transmission Impairment Measurement Set (TIMS). It is my understanding, that the TIMS input should be designed to see only the 1KHz demodulated signal originating from the EUT. It has become apparent that on more than one occasion that the TIMS itself has demodulated the test signal and displayed a reading that would indicate a failure. This seems to be a result of the modulated test signal coupling into the unshielded twisted pair connected to the analog voiceband channels of the EUT. Adding ferrites to the analog voiceband twisted pair leads improves the situation. I have thought of using a shielded cable, but there isn't a good way to terminate the shield at either end. Has anyone seen a similar problem? In summary it seems that in some cases, we are testing the measuring instrument, not the EUT. The TIMS seems to be sensitive to the modulated test signal. If this is the case, are some TIMS better than others? If so, what specification would indicate a TIMS immunity to the modulated test signal? Is there a more reliable instrument than a TIMS? Please feel free to call me if this would be easier. Thanks in advance. -----Original Message----- From: David Gelfand [mailto:[email protected]] Sent: Friday, September 08, 2000 11:07 AM To: [email protected] Subject: 90 V gas-filled arrestors source?
Hello group, Does anyone know who makes gas-filled arrestors called for in IEC 1000-4-5 coupling networks? Would a MOV be ok? Thanks, David. David Gelfand Regulatory Approvals Memotec Communications Inc. Montreal Canada
