[TowerTalk] wire antenna question

[Steve Hunt]

Gerald,

I agree that for most "normal" situations minimum VSWR and resonance are 
coincident. But I have given one example, and there are others, where 
they are not.

The values I quoted were taken from EZNEC VSWR plots, and confirmed in 
the VK1OD on-line calculator.

73,
Steve

TexasRF at aol.com wrote:
> Steve, when I plug your numbers into a transmission line program I get 
> these results:283.8 -j23.66 = 5.72 vswr (same as your example).
>  
> 288.2 +j0 = 5.7 vswr which is just slightly lower than example #1 but 
> illustrates better vswr when j=0.
>  
> I did not look into the 40 +j4 case but in general, real antennas show 
> a reactance change much greater than a resistance change when they are 
> in the range of one half wavelength. I would expect a reactance of 
> maybe 20 ohms (positive) for an increase of 5 ohms in the resistive 
> value. This would show a vswr of 1.55 which is higher than the 40 +j0 
> value of 1.25.
>  
> Perhaps someone can model a dipole to confirm or refute this.
>  
> 73,
> Gerald K5GW