[Elecraft] Attic Antenna

[N2EY at aol.com]

In a message dated 10/29/06 11:12:34 AM Eastern Standard Time, 
vic at rakefet.com writes:


> N2EY at aol.com wrote:
> > In a message dated 10/27/06 4:38:23 PM Eastern Daylight Time, 
> > rohre at arlut.utexas.edu writes:
> > 
> > 
> >> The Diamond bottom tube may, (and likely) contains a broad band ferrite 
> >> cable choke.  
> > 
> > Probably - to keep RF off the outside of the coax. Such a choke would cost 
> a 
> > few dollars at most.
> 
> Actually, a choke on the coax would *prevent* the antenna from working 
> unless it was mounted on a metal mast.  It needs a counterpoise and the 
> coax shield provides it unless a mast or radials are present.


Agreed. Note that in the literature, the unit is shown on a metal mast.

> 
> This is actually similar to the 'e-h' antenna, in which the alleged 
> 'antenna' at the end of the feedline serves to tune the shield of the 
> feedline to resonance.  The shield actually does the radiating.  Adding 
> a bead balun to an e-h antenna causes the antenna to stop working and 
> the balun to get hot!  No, I don't want to start a thread on this 
> antenna either!
> 

Good idea.

> In the Diamond antenna, the feedline is only half of the antenna, with 
> the 22-foot radiator being the other half and the resistor smoothing out 
> the SWR variations.
> 

Or the mast.

So what's probably in the "matcher" is really just a resistor.

$400 for 22 feet of tubing, a mast clamp, and a nice noninductive resistor.

73 de Jim, N2EY