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## Re: [TowerTalk] Ground Resistance

 To: John Cowan Re: [TowerTalk] Ground Resistance Bill Turner dezrat@copper.net Wed, 09 Aug 2006 09:49:37 -0700
 ```ORIGINAL MESSAGE: >I have followed the posts on radials and ground resistance for some time. Is >there any simple way to measure the impedance of the ground radial system as >you install them to know when you have enough of them in the ground? > >John ------------ REPLY SEPARATOR ------------ Here's the method I use with an SWR analyzer such as the MFJ-259 or similar: Understand that a 1/4 wave vertical over a "perfect" ground will measure a feedpoint impedance of about 36 ohms. This impedance is purely of the vertical part; the ground, if "perfect", has zero impedance. If you have additional ground impedance due to insufficient radials, the 36 ohm figure will go up and so will losses by a proportional amount. If, like many of us, your vertical part is shorter than 1/4 wave, you must make an approximation of what it actually is. The ARRL handbook and antenna handbook have graphs which will help. For example, if you determine that your shortened vertical is only 10 ohms, and you have a "perfect" ground, 10 ohms is what your SWR analyzer will measure. More likely, it will be higher than 10 ohms, and that difference is the additional loss caused by insufficient radials. Hope this makes sense. It's simple Ohm's law. Bill, W6WRT _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
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