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November 25th 04, 11:16 PM
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On Thu, 25 Nov 2004 21:11:13 GMT, Richard Clark
wrote: On Thu, 25 Nov 2004 20:20:32 GMT, (Robert Lay W9DMK) wrote: I have embarked on careful measurements of lines severely mismatched (quarter wave open circuit stubs), and I can find no correlation between my measurements and the values predicted by the "total loss" equation. My measurements always show very low losses in comparison to the model. Hi Bob, Looks like our two recent postings about roughly the same topic passed like ships in the night. How about the numbers (your data) that leads to your suspicions? 73's Richard Clark, KB7QHC The only one that falls immediately to hand is probably a decent representative example. It is a piece of RG-8/U, also known by its maker, Columbia, as 9913. It is 5.334 meters long and is approximately 1/4 wave at 10.6 MHz, which is where I made the measurement. In its open circuit configuration, it measures 0.57 + j 0.3 ohms. I am still struggling with some issues of how to interpret those results, but two things seem to be clear - 1) the reactive component is because I was about a degree too long for the frequency of measurement, or there is enough stray capacitance at the open circuit to transform into a bit of inductive reactance, and 2) the very low resistive component doesn't seem to fit any math models that I'm working with. What do you think? Bob, W9DMK, Dahlgren, VA http://www.qsl.net/w9dmk |
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