[Antennas] Half wave vertical question

Mon Dec 6 11:34:09 EST 2004

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年12月06日 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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