[mythtv-users] OT: Wiring a new construction home for A/V, Ethernet, etc

[Brian Wood]

On Wednesday 03 December 2008 11:48:49 David Brodbeck wrote:
> On Wed, December 3, 2008 8:05 am, Allen Edwards wrote:
> >>  > The other issue is grounds.  You want everything grounded to the same
> >>  > reference point.
> >>  >
> >>  > This goes for the TV antenna,
> >>
> >> That is pretty much impossible to achieve in practice, in part because
> >> of
> >> code issues.  In every jurisdiction I'm familiar with, a ground block is
> >> required on the exterior of the building in the immediate vicinity of
> >> where
> >> the downlead enters the structure; and a dedicated ground MUST be run
> >> from
> >> this block by the most direct path possible, even if that means (as it
> >> sometimes does) a separate copper rod in the dirt.
>
> You can still effectively create a single-point ground by bonding the
> ground rods together with a low-resistance conductor -- copper wire, say.
> Use a fairly heavy gauge, not so much for resistance reasons but because
> it will be less likely to corrode through and fall off that way.
>
> A single ground rod doesn't provide a very good RF or lightning ground, so
> in serious antenna installations it's not uncommon to drive several rods
> and bond them together.

For Radio transmitting antennas copper grid is often buried, and radials, 
sometimes up to a hundred or more, are buried and bonded together,

For AM directional rigs, absolutely HUGE ground radial arrays are often used, 
but this is not really relevant to MythTV installations :-)
-- 
beww
beww at beww.org