Posted by
N2EY on
Oct 29, 2006; 4:28pm
URL: http://elecraft.85.s1.nabble.com/Attic-Antenna-tp394788p394799.html
In a message dated 10/29/06 11:12:34 AM Eastern Standard Time,
[hidden email] writes:
>
[hidden email] wrote:
> > In a message dated 10/27/06 4:38:23 PM Eastern Daylight Time,
> >
[hidden email] 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
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