[Towertalk] OCF Longwire with moveable feed point

[Pete Smith]

At 02:23 PM 4/22/02 -0700, Terry O'Neill wrote:

>The athuor of the 1969 article (John Schultz, W2EEY) plots horizontal 
>radiation patterns for a 3.5 wl version @ 9 diffrent feedpoints along the 
>length of the wire.
>
>The  patterns are very interesting.


I just modeled a 3.5 WL wire 1/2 WL above ground, fed in the center, at 
each end, and at 25 percent of the length from one end.  The patterns are 
almost the same, regardless of the feedpoint location.  There is a wide 
bowtie pattern off the ends of the wire, with a number of minor lobes 
broadside.  Fed in the center, maximum gain is 8.26 dBi @68 degrees from 
broadside (and at the three other corresponding points).  Fed at one end, 
the pattern looks almost the same, but it is "tilted" a bit toward the end 
away from the feedpoint, with a maximum gain of 9.01 dBi at 70 degrees (and 
the three corresponding points).  The minor lobes nearest the ends are 
somewhat bigger, while those in the center are somewhat smaller than in the 
center-fed case.

As someone else observed, what does change significantly is the feedpoint 
impedance.  Modeled feedpoint impedance varies from 1280-j2062 at one end 
to 159+j65 in the center.

73, Pete N4ZR

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