[TriEmbed] more detail to the "attaching to the copper tubes" Re: OT: RF questions

[Brian]

On 9/29/20 8:06 PM, Pete Soper via TriEmbed wrote:
> One more detail that might be of general interest. The place where you 
> attach the xmit output and ground to the two dipole legs determines the 
> feedpoint impedance. If you attach to the closest practical two 
> positions near the center the impedance will be at or near what the 
> model predicted last night. So don't attach further out from the center 
> thinking it's arbitrary. It gradually increases such that at the 
> opposite ends it's several thousand ohms (i.e. phenomenally high SWR: 
> all heat, no RF out).

I think I had sort of absorbed that idea just from looking at graphic 
output from NEC2 (I found a cool port to C at http://www.5b4az.org/). 
It seems like the "ideal" case would be to have the distance between the 
inside ends of the dipole be as close to zero as possible without 
actually touching, with the feed attached right at the inside edge. e.g.

[------------][------------]
              ||
              ||

You wouldn't want to do this:
[--------]       [---------]
          |       |

Or this:
[------------][------------]
   |               |

My plan is to 3D-print a few little fittings to help line everything up.

Thanks again for the advice!
-B


> 
> -Pete
> 
> 
> 
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