another reason to have a better then average utility ground at your home
...in another discovery, a large Midwest IOU investigated and found more than
2,400 poles missing ground wires ...
http://tinyurl.com/2vudob2
http://www.beacononlinenews.com/news/daily/3120
http://www.och-c.com/topstories/2010/1111/111110wires.html
http://www.swvolusia.com/?p=8428
On Tue, Apr 5, 2011 at 11:19 AM, Roger (sub1) <sub1@rogerhalstead.com> wrote:
> On 4/5/2011 12:47 PM, Jim Brown wrote:
>> 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
>
> I would add "broadly centered" may cover an order of magnitude, but the
> farther out you go the fewer outliers you find. Even the super strikes,
> or positive lightning will not vary much outside that range even though
> the power contained in the harmonics may be substantial compared to a
> typical strike. It might help some to think of lightning as a really
> dirty 1 MHz signal<:-))
>
> A typical strike may induce over 1000 volts per meter in a conductor, be
> it an antenna, coax, telephone wire, or even house wiring. In a home
> that's say, 75 or 100 feet long including garage the voltages induced at
> one end of the building could be as much as 20 or 30 thousand volts
> different from wires at the other end of the home. That makes common
> grounds and common paths for wires entering the home essential.
>
> Just to keep it interesting my shop North wall is a good 160 feet from
> the South wall in the house. They are also on separate underground
> electrical feeds but from the same pole. There are 2 computers in the
> shop tied into the wired network with CAT6 cable and a telephone cable.
> The network and telephone runs are each 130' long. They are also tied
> into the ham stations in the house and shop. All electrical grounds are
> tied into the ground system for the towers and electrical feeds to both
> buildings. That system consists of a network of 33 8' ground rods and
> over 600 feet of bare #2 copper plus the two electrical system ground
> rods at each service entrance for a total of 37 ground rods although the
> ones required by code at the entrances are relatively anemic compared to
> the rest of the ground system.
>
> 73
>
> Roger (K8RI)
>
>> 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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>
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