[mythtv-users] Attic antenna

[Brian Wood]

On Friday 28 August 2009 14:58:50 David Brodbeck wrote:
> On Fri, August 28, 2009 1:37 pm, bhaskins at chartermi.net wrote:
> > Questions:
> > I have read that the old style 300 ohm twin lead has a lower loss
> > per foot than coax.. true/false ?
>
> True.  However, you have to keep it away from metal and other wiring -- at
> least twice the width of the line.  This is because the electromagnetic
> field extends into the air around the conductors, whereas with coax it's
> contained within the shield.

Also, twinlead is prone to "ingress" problems, signals that exist in the air 
will get into the twinlead and cause interference, front-end overload of the 
receiver and other problems.

This sort of problem is somewhat reducedby phase cancellation of a signal 
which "ingresses" into both sides of the balanced twinlead equally, but it's 
still a problem.

Coax, being shielded, is resistant to the ingress of outside signals.

Generally twinlead works well in "quiet" electromagnetic areas like rural 
areas, but is problematical in urban areas with a lot of RF floating around 
the environment.

-- 
Brian Wood
beww at beww.org