[Lowfer] Common Mode Chokes (was Active Whips)

[Douglas D. Williams]

I only ground my receive system at the base of the antenna. I leave system
ungrounded on the shack end, and I'll show you why.

Here is a picture of 0 - 48 kHz with the coax shield grounded at the
antenna base and again grounded in my shack, which is 50' away:

https://dl.dropbox.com/u/33457409/z1203grounded.JPG

Here is the same spectrum taken 5 minutes later with the shack end
ungrounded, and the antenna base still grounded:

https://dl.dropbox.com/u/33457409/z1203%20ungrounded.JPG

Obviously, in my location, the latter arrangement is superior. When I
showed this to Jack at Clifton Labs he explained it to me, and again I
paraphrase from the best of my memory, that it is due to induced ground
currents (or something like that). I may still have the
e-mail.....somewhere.

Note that these pictures were taken before I had installed any common mode
chokes. It may be quite different now. I should repeat the experiment.

73, Doug KB4OER

On Thu, Jan 24, 2013 at 8:27 PM, Pat Bunn <pbunn at patbunn.com> wrote:

> I followed Jacks advise and have a choke about ten feet from the base of
> the antenna with two driven ground rods.(l also have 2 rods at the antenna
> base. The choke ten feet from the antenna is grounded on the antenna side
> (I used a TV type ground to ground the shield)
>
> I have another choke at the receiver end with again a good driven ground
> on the antenna side of the choke.
>