[TenTec] 75 Ohm twin velocity factor ?

[Steve Hunt]

Jerry,

How do I get that? ..... mental aberration and mis-interpretting the "brackets", that's how :)

At the risk of extending this thread for far too long .... what would happen if you "parallel connected" two lengths of 300 Ohm twin sitting on top of one another. Would the composite Zo be half the individual value (as it would be with coax), or because the fields would interact, would it act more like a single entity with fatter conductors but separated by the same distance?

73,

  ----- Original Message ----- 
  From: Dr. Gerald N. Johnson 
  To: tentec at contesting.com 
  Sent: Saturday, January 27, 2007 4:59 PM
  Subject: Re: [TenTec] 75 Ohm twin velocity factor ?

  How do you get that? I tried 0.1" diameter conductors 0.11" center to
  center and it comes up 53.2 ohms impedance. That's 0.010" gap, fairly
  closely spaced. Same conductors 0.105" center to center (0.005" gap) is
  37.79 ohms impedance. Cut that gap to 0.001", 0.101 gives 16.96 ohms
  impedance. That's 120 arccosh (S/d). S is center to center spacing, d is
  conductor diameter. Working closer, 0.0001" gap for 0.1001" center to
  center gives 5.37 ohms. So lower impedances are possible, maybe not
  practical, but possible. 10 millionths gap makes 1.7 ohms, 1 millionth
  gap makes half ohm impedance. But yet the conductors don't quite
  intersect or touch unless the gap gets all the way to nothing. And then
  the impedance is zero.

  -- 
  73, Jerry, K0CQ,
  All content copyright Dr. Gerald N. Johnson, electrical engineer

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