[TenTec] Station and AC Ground

[Gary Hoffman]

----- Original Message ----- 
From: "Martin, AA6E" <martin.ewing at gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Tuesday, November 29, 2005 5:25 PM
Subject: Re: [TenTec] Station and AC Ground


> 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. ;-)

Well.....If I had appreciable amounts of RF on the outside of my coax, which
I don't due to the heavy chokes I use at the ends, then I can imagine a path
for RF to flow from my power amplifier into the ground strap.  It might then
radiate something.  Of course, as it is, the only possible path for the RF
is out of my PA, through the center of the coax,  and into the antenna.
Now, I admit the ground strap might pick some of the antenna's radiation
up, and re-radiate it, but I doubt this would amount to much.

As for only working at discrete frequencies, not so.  It would be "close" to
a half wave all across one band.  Thus "close" to a perfect ground across
the whole band.  Naturally you would need one per band.


>
> 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.

I agree that skin effect and resistive and reactive impedance are of vital
importance.  You may have noticed in my note that I said I used  very large
diameter refrigeration tubing for my grounds.  Excellent for skin effect and
wide surface area for low inductance and resistance.

Mulitiple ground rods are absolutely essential in regards to this
consideration also.  A single 8 foot rod is unlikely to couple to earth
sufficiently.

73 de Gary, AA2IZ