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## Re: Topband: Tophat? Does it have to be at the top?

 To: "Earl W Cunningham" , ,, ,"Jon Zaimes AA1K" Re: Topband: Tophat? Does it have to be at the top? "Tom Rauch" Tom Rauch Thu, 10 Jun 2004 06:05:15 -0400
 ```Watching frequency shift to determine current distribution is a great deal like the misplaced notion we can grab the jacket of coax and watch SWR shift to tell if we need a balun. Every Yagi would appear as a capacitance on 1.8MHz, the value of which doesn't change much with height. Where you place the capacitance most certainly has an effect on current distribution in the tower. The amount of effect depends on the ratio of the impedance of the tower system where the Yagi is placed to the impedance of the capacitance of the Yagi. In some cases the Yagi will make "change for the good". In some cases it will make a "change for the worse". Sometimes it will do nothing noticeable. The best solution is to model the system as closely as possible with real losses (as real as a model can get) and see if the Yagi's are helping or hurting field strength by adding and removing them or repositioning them. There are very few hats that 100% stop all current beyond the hat, since it is really an impedance ratio problem and the hat is almost never near zero impedance and the area above the hat almost never near infinite impedance. Adding a hat can do about anything from the range of positive to negative effects depending on many separate issues. 73 Tom _______________________________________________ Topband mailing list Topband@contesting.com http://lists.contesting.com/mailman/listinfo/topband ```
 Current Thread Re: Topband: Tophat? Does it have to be at the top?, (continued) Re: Topband: Tophat? Does it have to be at the top?, Mike Harris Re: Topband: Tophat? Does it have to be at the top?, Milt Jensen Re: Topband: Tophat? Does it have to be at the top?, Bob Tellefsen Re:Topband: Tophat? Does it have to be at the top?, i4jmy@iol.it Re: Topband: Tophat? Does it have to be at the top?, Cqtestk4xs Re: Topband: Tophat? Does it have to be at the top?, Earl W Cunningham Re: Topband: Tophat? Does it have to be at the top?, Guy Olinger, K2AV Re: Topband: Tophat? Does it have to be at the top?, W5PR Re: Topband: Tophat? Does it have to be at the top?, Jon Zaimes AA1K Re: Topband: Tophat? Does it have to be at the top?, Peter Sears Re: Topband: Tophat? Does it have to be at the top?, Tom Rauch <= Re: Topband: Tophat? Does it have to be at the top?, Ford Peterson Re: Topband: Tophat? Does it have to be at the top?, Earl W Cunningham Re: Topband: Tophat? Does it have to be at the top?, Herb Schoenbohm Re: Topband: Tophat? Does it have to be at the top?, Guy Olinger, K2AV