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## Re: [TowerTalk] dipole length adjustment

 To: Bill Turner , "Dave Tipton" Re: [TowerTalk] dipole length adjustment Jim Lux Fri, 19 Jan 2007 14:13:59 -0800
 ```At 06:15 AM 1/19/2007, Bill Turner wrote: >ORIGINAL MESSAGE: > >On Thu, 18 Jan 2007 21:24:19 -0800, "Dave Tipton" > wrote: > > >(468/Original Frequency) - (468/New Frequency) = Length to shorten in Feet > >------------ REPLY FOLLOWS ------------ > >While the above method will probably work well enough, there is a >slightly more accurate method, since it does not depend on the >accuracy of the 468 factor to begin with. The 468 factor can be >affected by the closeness to earth and nearby objects and/or antennas. >The following method takes those things into account automatically: > >Divede the actual resonant freq by the desired resonant freq to get a >factor, typically between .98 and 1.02 or so. Multiply the original >length by that factor to get the new length. Add or subtract wire as >needed, more wire if the desired freq is lower, less wire if the >desired freq is higher. > >For example, if the actual resonant freq is 7150 and the desired freq >is 7010, the factor is 7150/7010=1.02. If the original length was 66 >feet, the desired length is 66*1.02=67.32 feet. One caveat, which seems obvious once you know it, is that this works only for changes of a few percent. Don't go trimming your 80 meter dipole for 40 meters by doing this... Jim, W6RMK _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```