In Reply to: To Jon Risch: re Transmision lines posted by Wade on November 18, 1999 at 13:44:21:
You are not so much concerned about the phase of the line opening signal anyway, so measuring this might be somewhat misleading.The best way to assure T-line tuning is to measure a very accurate and detailed impedance curve, so as to assure a nice flat curve at driver resonance. To little damping causes the classic double hump of a vented cabinet, while too much starts to look like a selaed box, with a single mild peak at system resonace.
The frequency of this dip or slight hump is the tuning frequency, and it should be in the middle of the impedance lumps/humps that are residual.
Ideally, a perfectly tuned line would look like a resistor, but most well tuned lines have a hint of a very braod and mild hump, due to a slight amount of overdamping. This is preferable to ANY amount of dip.
Jon Risch
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