Recently several of our customers have began asking for impedance testing to be performed at various frequencies, from 200 Megahertz to 1 Gigahertz. From what I have been told about TDR operation, the device works with a carrier frequency of between 10 Megahertz and 20 Megahertz, and a response frequency in the "X-band" of approx. 1.5 to 2 Gigahertz. Can anyone shed some light on what TDR test frequencies are and how they should be specified? Hal Brown Zycon Corp. [log in to unmask] (408)261-4019 voice (408)244-6349 fax.