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## Re: [TowerTalk] Ladder line through the wall

 To: Re: [TowerTalk] Ladder line through the wall "Tom Rauch" Tom Rauch Wed, 25 Aug 2004 22:33:40 -0400
 ```> With the help of my trusty ITT Blue Book, I can calculate the impedance > of a balanced line passing through a grounded pipe. If your line is 450 > ohms in free space with air dielectric, the balanced shielded line has > the following impedance: > > If shield dia. is 2 x the wire spacing, Zo = 388 ohms. > If shield dia. is 4 x the wire spacing, Zo = 434 ohms None of this matters, because to have a significant impact on line SWR the impedance bump has to be a significant fraction of a wavelength long. On TV channels, a six inch long bump of 2:1 SWR would be significant in a MATCHED line...but insignificant if the line is already operating at high SWR. Pass the line through the wall in 2" PVC, and don't worry about a thing. If the wall is 3 feet thick and metal the whole way through, and you operate the line at 1:1 SWR with wideband video signals at 30MHz, you might see some ghosts in the video. For amateur applications and normal walls there won't be a problem in the world. Pass it through the PVC conduit and have fun. Just be sure to have a lightning gap outside. 73 Tom _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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