> Has any made a vertical dipole (lets say for 20
> meters) where it is end fed with coax.
Tom,
Why not make a trap at the bottom out of coax??? Use a 1/2
wl of coax as the radiator with the shield cut 1/4 wl back
from the open end.
Tie the shield and center together at the ends of the outer
section.
Like this:
_______ _______
I- - - - - I----------------Coax Shield Isolator --Feedline
_______ _______
You would have a symmetrical diameter dipole, and by winding
the coax in a nearly self-resonant solenoid and adding only
enough parallel C to make it resonant, you could get pretty
good isolation.
To make the isolator, you could wind RG174 in a single layer
and put a high voltage 20-50pF capacitor across it from
shield to shield at each end. Adjust the turns spacing
until resonant.
I'd make the whole antenna out of RG-174 or similar. Two
isolators spaced 1/8th wl would be better.
73 Tom
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|