[TenTec] Coaxial cable for ground wires

Jerry Volpe kg6tt at arrl.net
Tue Oct 17 00:49:47 EDT 2006

I submitted this coax cable as a way to work effectively where your 
ground wire is longer than a few feet a number of times on different 
reflectors over the years. It is especially useful for those with second 
floor stations.

Using a shield cable for an isolating DC ground is something I learned 
many years ago when I was a practicing RF Engineer. Without getting into 
the crazyness of it all... what this does as a circuit is to basically 
take advantage or the 'skin effect' property of a conductor carrying RF. 
RF radiated from the antenna system is picked up on the shield of the 
coax ground and then travels along the outside skin of the shielded 
cable (use good quality cable here). As a circuit the RF travels toward 
Earth ground. Due to the skin effect of the shield the coupled RF energy 
does not penetrate through into the inside conductor so RF is 
effectively shunted to ground. Meanwhile the inner conductor acts 
primarily as a DC ground regardless of its length (within reason) which 
is its intended purpose.

Years after first learning about this I experimented with mix 43 ferite 
beads placed at the open end of the coax shield at the shack end of the 
circuit. If you want to add the ferrites you will probably want to use 
at least 10 or more spaced an inch or so apart. You want to create a 
very high impedance. Remember, the ferrites go at the shack end of the 
ground and the center and the shield conductors are connected together 
to a good ground rod while only the center connector is used in the 
shack. I further recommend the ground connect to a single point and then 
fan out to the essential equipment. I know this is going to bring up a 
lot of discussion. Anyway, if you use an antenna tuner then this would 
be the best place to connect this shielded ground.

For the person who suggested that a good operator doesn't need a ground 
in their station (something to do with "what is that terminal for on the 
back of a Triton IV)..... have you ever heard of 'near field' effect of 
a transmit antenna? Do you know how far out the near field extends say 
on 80 meters? Say on 20 meters? 10 watts? 100 watts? 1500 watts? Few 
hams can install their equipment at such an impractical distance to get 
outside the near field (which is really an RF hot spot) nor install 
their shack in a grounded RF shield room. Anyway, the primary purpose of 
the ground is safety, although receivers work better (quieter too) when 
the rf front end has a completed RF circuit for the minute antenna 
currents to flow through. This requires a good antenna and a good Earth 
ground. Basic AC electrical theory here.


Jerry, KG6TT

Ralph Jerald "Jerry" Volpe
Amateur Radio Operator KG6TT
ARRL Member & VE
FISTS 12304

788 Chestnut Drive
Fairfield, CA 94533

kg6tt at arrl.net

510 325-7724
707 399-8838 FAX

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