You can have a tuned "ground" but it only works at discrete
frequencies. Besides, any current-carrying wire of appreciable
length, tuned or not, becomes part of your antenna system. If, as it
should, the RF ground carries no current, an open circuit will work
just as well. ;-)
For lightning (a broadband pulse), what matters is impedance of your
ground connection. Resistive (considering skin effect) and reactive
(inductance). Wide copper stap as short as possible minimizes
effective resistance and inductance. A half wave wire (cut for some
wavelength) is unlikely to be good for lightning.
73 Martin AA6E
On 11/29/05, Gary Hoffman <ghoffman@spacetech.com> wrote:
> >
> > The first (RF) is somewhat hopeless, as was pointed out, because a
> > real (broadband) RF ground has to be very short, say not more than
> > 1/10 wavelength, to avoid reactive and resonant effects. That means
> > shorter than 1 meter for 10 meter operations, etc. That's not
> > practical in most installations. You don't really need a "true" RF
> > ground, if your antenna system is balanced properly - no common mode
> > RF on the feed lines, etc.
> >
>
> Or....a half wave ground wire, to repeat the low impedance at earth right at
> the radio.
>
> And, since lightning is RF, I feel that a real RF ground is important, even
> for lightning.
>
> 73 de Gary, AA2IZ
>
>
>
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--
martin.ewing@gmail.com
http://blog.aa6e.net
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