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## Re: [TowerTalk] SteppIR cable capacitance (was: SteppIR problem)

 To: "Tower Talk List" Re: [TowerTalk] SteppIR cable capacitance (was: SteppIR problem) "Jim Brown" Mon, 11 Jun 2007 12:20:11 -0700
 ```>Twisting always increases capacitance between pairs. Hmmm. Twisting WILL, of course, increase the LENGTH of the conductors a bit, which will increase the capacitance by that proportion. But the question is, HOW MUCH does it increase? I recently untwisted some #14-2 and 16-2 twisted pair to use as radials. The difference in length between twisted and untwisted was less than 10%. Consider CAT5. It is VERY tightly twisted with a very short lay (a lot of twists per unit length), but its capacitance approaches the lowest capacitance cable I know of. Conductor size also contributes to capacitance, with smaller conductors having less capacitance. So making conductors larger increases capacitance. Does that mean we should use only #40 pairs? This fixation on cable capacitance reminds me of the late Dick Heyser's comment that trying to describe an audio system with only one parameter -- its frequency response -- was like trying to write poetry with only one word in your vocabulary. Heyser was a very bright guy whose day job at JPL was designing communications for the space program. He was the inventor of Time Delay Spectrometry, and held a dozen or so patents in fields ranging from medical electronics to underwater sound to audio. TWISTING is a powerful rejector of interference in any system, and especially in a balanced system. Twisting is good for at least 20- 30 dB. If it adds a few hundred pF to a circuit that already has 0.1uF (or even 0.005uF), who cares? Jim K9YC _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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