[BC] Air-Dielectric Sections

[Phil Alexander]

On 6 Mar 2007 at 0:05, Rob Atkinson wrote:

> 
> Phil,
> 
> just trying to learn something--how is rigid line 
> normally run below grade?  
> That is, what is it usually placed inside of?
> 

Usually, it is not run below grade. However, when it 
is done properly, it would have to be placed in something 
like a steam tunnel. Rigid typically comes in 20 ft. 
sections and a rigid run does require maintenance. Unless
there are other things in the same run like steam, water, 
telephone, utility power etc., or overriding reasons, I 
would never consider putting rigid line underground in 
this day and age. Today we have air dielectic Heliax 
and that can go u/g safely in three different ways, all 
of which have been discussed on this list in the past, 
and mentioned in this thread to a limited extent.

For an existing AM plant, directional boring is probably 
the best, taking the ground system into consideration. 
Where that is not a problem, such as a new build-out AM 
plant, or for a horizontal FM run, I'd be inclined to give 
the fiber duct that Mike mentioned first consideration. 
For a new plant, there is also always the old standby of a 
PVC liner inside clay or concrete pipe to consider, but 
I would never consider bare PVC. That is just asking for 
trouble, especially where the ground freezes during winter.

---------------------------------------------
Phil Alexander, CSRE, AMD
Broadcast Engineering Services and Technology 
(a Div. of Advanced Parts Corporation) 
Ph. (317) 335-2065   FAX (317) 335-9037