Mike,
The skin effect has nothing to do with the quality of the RF ground from the
equipment to your central ground point.
Historically, amateurs have used either large conductor copper wire (AWG 8,
6, 4, or even 2) as well as 1 inch or 2 inch copper braid for connecting
their equipment to their ground system. Many times even these measures are
not the most effective especially if there is a longer run than about 6 or
so feet to the ground point.
The key to a good RF ground for your equipment is to have the Lowest
Inductance which means the lowest inductive reactance at RF frequencies. The
best way to accomplish low inductance RF grounds from your equipment to the
ground point is by using a wide solid copper strap (3 to 4 inches) wide from
your equipment to your ground point, such as the ground rod field.
I have a solid copper bar going across the back of my equipment desk that
bonds to a 4 inch wide solid copper strapping that I run from my equipment
outside to the ground rod array.
The key is providing a LOW INDUCTANCE path to the ground field. This ground
strap is the same kind of material that Polyphaser recommends with their
solid copper grounding panel that can be mounted in the vicinity of the
equipment.
Remember, the inductive reactance XL is equal to j omega L, and Omega is
equal to 2 PI frequency, therefore, the XL increases with frequency, and you
want the lowest XL possible at RF frequencies, so you need to keep the L
very low. You do this with wide copper straps (solid) going from your
equipment consolidation point to your ground field consolidation point, with
the shortest run of strap possible.
Not many hams want to go to this extent, however, this is what it takes to
make it truly effective.
PolyPhaser has some great technical articles about the need for Low
Inductive paths at RF.
For DC grounds it does not matter, you only have to have a large enough
conductor to handle the current load under a power surge or nearby lightning
strike that provides either a large EMP on your ground field or via your
power lines coming into your house.
Hope this helps.
Thanks,
Jim
K4PV
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]On
Behalf Of Mike Bryce
Sent: Sunday, January 07, 2007 10:28 PM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] A grounding question
Guys...
I've got a 8 foot copper ground rod hammered into the basement where
the shack lives. From that ground rod I have 2" wide copper braid
going to 1/2 inch wide by 1/8" copper strips.
The various radios and tuners, power supplies and what nots are tied
to these copper strips with short hunks of braided copper. (shield
from old RG8 cables) The equipment is NOT daisy chained together.
From what I have been reading, all of what I have described above is
NO good. Great for DC grounding, but zip for RF.
While surfing the net, I came across an article on Ameriton's site
that says braided copper should be avoided at all costs as this makes
a really crappy RF ground.
They recommend at least 2" wide solid copper strips. Siting the "skin
effect"
I was always under the idea that skin effect only occurs on
frequencies higher than 30 mhz.
So, what do the experts say??
mike
Mike, WB8VGE
SunLight Energy Systems
The Heathkit Shop
http://www.theheathkitshop.com/
J e e p
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