[GreenKeys] Questions on troubleshooting an antenna

[hwhall at compuserve.com]

> The next inch, no matter where I tap it,
> I have an infinite SWR from 1.7 - 33MHz.
> Now the really weird thing happens: once I pass the infinit-SWR zone,
> as I tap the coil, higher and higher, the frequence of resonance drops:


My first guess is that you have so much coil there that at some tap points
and freqs it acts like an RF choke between the vertical element and the 
ground plane. I think you have the coil connected between the ground plane 
and the vertical element? Disconnect the bottom end of the coil, leave the 
top of the coil attached to the element. Connect coax shield to groundplane.
Tap the coax center conductor on the coil working downward from the topmost 
turn. That should put the fewest turns in circuit for any freq. 

Watch out for the open circuit end of the coil to try to do a high voltage 
brush discharge. With so many turns it will act like an autotransformer. 
This is why some large coils have shorting placed across the unused turns.
But I think you just need to find out how many turns you can clip off. 

Wayne 
WB4OGM