View Single Post
  #32   Report Post  
Old May 6th 09, 12:13 AM posted to rec.radio.amateur.antenna
Jim Lux Jim Lux is offline
external usenet poster
 
First recorded activity by RadioBanter: Mar 2007
Posts: 801
Default Station With Center-Fed Dipole - Best Grounding Technique?

dave wrote:
Jim Lux wrote:
Howard Lester wrote:
"dave" wrote

A BalUn would help a lot.

For what? If the antenna system is balanced (as are dipoles,
inherently), I seriously doubt a balun would be good for anything.


Most every practical dipole installation has some imbalance in the
installation (the trees are closer to one side than the other, etc.)..
a choke to prevent RF current from flowing on the outside of the
feedline will at least make the pattern more consistent with
expectations. Might make the tuning less "twitchy" too (because you've
decoupled the effect of things near the feedline).

Certainly, a choke at the entrance to the shack is a great way to keep
RF outside.


A choke wastes power.


How might this happen? The choke's not in the desired RF path (i.e. the
inside of the coax and the antenna itself)

Putting an RF impedance of, say, 5K in series with the current on the
OUTSIDE of the shield should effectively reduce the current to zero, so
there's no power being dissipated in the choke.

Yes, if you use a choke with too low an impedance, it might dissipate power.