[Amps] 2 more questions-- electrical

Jim Brown jim at audiosystemsgroup.com
Tue Apr 5 09:47:00 PDT 2011


On 4/5/2011 7:59 AM, Bill, W6WRT wrote:
> REPLY:
>
> If you are getting RF in the shack, you do not have a grounding problem,
> you have an antenna problem. You do NOT need an RF ground at your shack
> in any way. The only grounds your shack needs are for safety of the AC
> mains and for lightning.
>
> RF in the shack problems indicate an unbalance in the antenna and/or
> feedline system and can almost always be cured by proper application of
> a balun or unun.
>
> RF energy is expensive to generate. Do not waste it by running it
> through dirt. Get it up in the air where it belongs.

RIGHT!

Back to Charles's question about which ground is better.  The answer is 
that it doesn't matter -- ALL MUST BE BONDED TOGETHER, which makes them 
effectively in parallel.  In addition to lowering the impedance to 
earth, that also reduces the potential difference between different 
points in your building in the event of a lightning event, which in turn 
minimizes the likelihood that something is going to fry.

As to the power company's ground rods -- THEY DON'T MATTER! LIGHTNING IS 
NOT A DC EVENT, it is an IMPULSE, with VERY STRONG harmonics. The energy 
in lightning  is broadly centered around 1 MHz, so what matters is the 
IMPEDANCE of the path to ground, which, if you do the arithmetic, is 
dominated by the  INDUCTANCE of the connecting wires.

73, Jim Brown K9YC


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