[Antennas] Half wave vertical question

[wb8owx at fuse.net]

I have Cushcraft R5 which is a halfwave vertical, in the base they use a 4:1 torriod into a 1:1 balun to the coax.  They also have a 50pf transmitting cap (doorknob) in series with the vertical between the vertial element and the torroid. 

You can see a diagram of this home brew version..

http://www.qsl.net/ei7ba/r7_vertical.htm

Seems to work for them...

73, Tim 
K8WBL







> 
> From: "Richard Brunner" <rbrunner at gis.net>
> Date: 2004/12/06 Mon AM 07:57:44 EST
> To: "Antennas" <antennas at mailman.qth.net>
> Subject: Re: [Antennas] Half wave vertical question
> 
> The end of a half wave antenna is a voltage maxima, and impedance will be 
> "about" 4000 Ohms.  Matching with a toroid will be difficult to impossible. 
> I suggest a quarter wave of open-wire line connected directly to 50 Ohm coax 
> to the shack.  At the antenna end one wire goes to the antenna, and the 
> other is floating.  With a half-wave antenna you don't need a ground grid, 
> but it will do no harm.  (Other advice will undoubtedly differ...)  You can 
> also use a resonant tank, link coupled, or an L network.
> 
> Richard Brunner, AA1P
> 
> ----- Original Message ----- 
> 
> >I have read that the impedance of a half wave vertical CAN be several
> > thousand ohms. My question is how many thousands. The feed point will be 
> > approx.  6
> > inches above ground at my location. I have 6 quarter wave radials in 
> > place. I
> > am trying to match this antenna to a TinEar receiver that I recently 
> > built. It
> > requires a 50 ohm input. I would like to wind a toroidal transformer to 
> > match
> > these two, but don't know the ratio I will need. Any help would be
> > appreciated.  Rick
> 
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