LF: Re: Re: Noise cancelling by using optic transmission of RX signals

["Chris Trask" <christrask@earthlink.net>]

>
> > I think the role of the ground with active whips is often neglected -
the
> > output of the whip preamp is the voltage differential between the whip
> > element and the circuit ground, so the ground connection is just as much
> > part of the antenna as the whip element itself is.
>
> That's an important point that is often overlooked or ignored. A mini whip
> mounted up at 5 meters is a 5 meter antenna. You can easily prove this by
> mounting it at ground zero on top of a ground
> screen. Been there, done that.
>

    I can see how this would be true if the preamp is connected to the
"actual" ground, meaning the earth's surface, and the whip.  But the
connections from the ground and whip to the preamp would also constitute an
antenna since they are exposed to the EM field and cannot be of zero length.

    You could, however, condition the whip to avoid this.  By using a
coaxial cable of some sort from the ground to the whip, the inner and outer
conductors would have the same voltage induced by the EM field and then TEM
coupling.  A transformer winding would have a first winding connected from
the inner conductor to the whip, and a second winding from the outer
conductor to the preamp.  That would subtract out the voltage resulting from
the path to ground.

Chris