Published: TV Technology

Issue: 8/28/97



Broadcasters Have Options To Tower Replacement

By Joe Fedele



MIAMI--With DTV deadlines looming, many stations are now actively looking at their towers and 

trying to determine a course of action for the installation of a new antenna system.  Although 

some stations find themselves faced with the unavoidable (and costly) prospect of having to 

replace there existing tower, others are taking a much more cost effective approach.

        

Tower renovations and reinforcement remain a key alternative to fabricating a new one.  The 

costs associated with this type of work is directly related to such things as the number of man 

hours spent on the refurbishment and the cost of guy wires and the steel itself.  

        

Oddly enough, the tower redesign plan itself is generally taken for granted and not always very 

well thought out. An organized renovation plan can often mean the difference between an 

expensive upgrade and a cost saving investment that could pay for itself and even provide rental 

space for more than just a new DTV antenna.  

        

Jim Tiner, President of the Tiner Companies (which owns Tower Network Services and Tiner 

Communications Service Inc.), notes that a great number of chief engineers are not aware of the 

many alternatives available to them when they look at tower refurbishment. Consequently they 

donÕt always know what to ask for from their tower service provider.  

        

"Many chief engineers are burdened with the responsibility of implementing the DTV conversion 

but are not always aware of the many possibilities for better utilization of their existing tower and 

at the same time maximizing their DTV coverage." he said. 

        

Many broadcast towers are now either at or near their maximum load carrying capability. Some 

broadcasters are faced with the problem of having to reshuffle the locations of the antennas 

mounted on it.  All too often the crucial question of which antenna will get the prime real estate 

on top of the tower becomes a difficult decision as broadcasters wrestle with their NTSC to DTV 

conversion plan.

        

In some cases broadcasters plan to to take the easy path in their implementation by simply 

installing a side-mounted DTV antenna somewhere low on the tower.  Some time in the future, 

however,  they will have to reshuffle the antenna to the top position when their DTV audience 

reaches a yet unknown theoretical limit at or near the end of the so called "NTSC/DTV simulcast 

period."

        

But maximizing a towerÕs potential today is a key point to Tiner, who emphasizes long-term 

planning when he evaluates a tower. "Remember," he says, "you will be stuck with this tower for 

a long time.  A well-planned co-location can avoid a costly second reconfiguration at the 

end of the simulcast period. Companies should also explore the redesign as a comprehensive 

plan for the inclusion of rental producing antennas that will offset the cost of maintaining the 

tower."

        

Although most tower companies can provide routine maintenance, such as simple tower repairs, 

painting and guy wire tightening, not all of them have the type of resources and expertise to 

perform a "creative redesign" or modification.

        

A typical reinforcement job could consists of merely adding steel to the existing structure or 

enhancing the guy wires. But "creative redesignÓ work goes beyond traditional thinking in tower 

upgrades.  Any structural engineer can analyze the tower, but not everyone can do the creative 

part.  And that evaluation must include the structural analysis and the predicted RF performance 

analysis.

        

An example of this is when stations install a side-mounted antenna instead of a top-mounted 

one, due to the limitations and configuration of their existing tower. The problem with this is that 

side-mounted antennas often deliver coverage that is inferior to top-mounted ones.  A top-

mounted antenna provides an unobstructed radiation pattern not effected by multipath or 

scalloping that would occur with a side-mounted version.

        

"Antenna manufacturers often sell side-mounted antennas prematurely," Tiner says, "without the 

benefit of a solid, long-term plan."  He adds that simply throwing up a side-mount is quick and 

easy but not very smart.

       

Tiner is currently working on several redesigns that will include actually removing the top section 

of a tower, moving the guy wire attachments and then top-mounting a combination NTSC/DTV 

antenna.  (see "proposed" diagram on right).

        

In this example, the tower AGL (Above Ground Level) height remains the same.  Maintaining the 

AGL is an important factor in many tower renovations because any change in tower height must 

be approved by the Federal Aviation Administration (FAA). The time, paperwork and legal 

resources required for such changes can often be costly and undesirable. And, in some cases, 

the FAA may not allow stations to extend their towers even one foot. 

        

"What we have found through our studies is that, without exception, top-mounted, co-locating 

with the NTSC antenna is practical and extremely cost-efficient, versus the cost of purchasing a 

new tower."

        

The most important thing to remember, Tiner emphasizes, is not to make any decision regarding 

your tower until you have gathered sufficient information. "Gathering the information is cheap," 

he said, "but making the wrong decision can be very costly."





EDITOR'S NOTE:  THE DIAGRAM MENTIONED IN THIS ARTICLE WAS NOT AVAILABLE FOR POSTING.  A DESCRIPTION

                OF IT IS LISTED BELOW.



DIAGRAM CAPTIONS: These drawings show how a tower can be modified to support both an 

NTSC and DTV antenna while maintaining overall Above Ground Level. The redesigned tower 

(at right) is capable of supporting both antennas in a top-mounted configuration, rather than a 

side mount, and still allows for additional tower leasing.