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## Re: [TowerTalk] Pattern Distortion caused by faulty balun?

 To: Re: [TowerTalk] Pattern Distortion caused by faulty balun? Mon, 2 Jan 2012 02:41:00 -0000 mailto:towertalk@contesting.com>
 ```What coax cable has a velocity factor of > 95? To: towertalk@contesting.com Subject: Re: [TowerTalk] Pattern Distortion caused by faulty balun? From: Steve Hunt Date: Sun, 01 Jan 2012 21:57:54 +0000 Tony, It would be the length from the feedpoint to the ground; you also need to factor in the Common-Mode velocity factor of the line - probably in the range 0.95 to 0.99. If I model that feedline length connected to a half-wave 20m dipole, assume a velocity factor of about 0.97 and a ground connection resistance of 10 Ohms, I get 40% of the leg current flowing back down the shield as CM current. If you are trying to estimate whether or not the conducted CM impedance is high or low at the feedpoint, remember you need to do it for all bands on a multiband antenna! 73, Steve G3TXQ On 01/01/2012 21:30, Tony wrote: > The total length of feed line to the rig is about 85 feet. It's > grounded at 70 feet where it then goes into the shack using a 15 foot > jumper. Which do you take into account as being a multiple of > half-wave? The total length of the coax or the length between the > antenna and ground? Tony _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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