Design, Installation and Maintenance of Antennas, Towers and Rotators

By Frank Donovan W3LPL

for Storm Survival, Long Term Reliability

and Safety

Dayton 2013 1

A Typical Tower and Antenna

Your Tower in its Environment

Dayton 2013

Adequate load capacity for current and future use antenna loads

especially unbalanced or unidirectional loads coaxial and other cables

Adequate load capacity for local environmental conditions wind loads (especially severe site specific conditions) ice loads (especially severe site specific conditions)

Unidirectional or unbalanced ice and wind loads Corrosion protection

including site specific conditions

Tower SectionsDesign and Construction

Dayton 2013

Beware of used or corroded tower sections with tubular legs

Inspect all tower sections one year after installation then at least once every three years after every serious storm after any structural damage to the tower

Check plumb and twist of the tower

Pay special attention to damaged, loose, missing or corroded: diagonal and horizontal trusses, welds and hardware especially at and close to the guy attachments

Tower SectionsMaintenance and Inspections

Dayton 2013

Beware of used or corroded tubular tower sections

Regular inspections are key to safety and long term tower and antenna survival

Use the manufacturer’s recommended design provide adequate depth for local frost conditions

The top of your foundation should be at least six inches above grade

Towers with tubular legs embedded in concrete require careful attention to reliable drainage during construction each leg must drain into gravel at bottom of the foundation concrete embedded tower sections are a risky practice in salt air

or corrosive industrial environments

Tower BaseDesign and Construction

Dayton 2013

Your tower base must provide reliable drainage for tubular tower legs

Inspect at least once every three years

Pay special attention to: corrosion at the tower-to-concrete interface standing water on the foundation dirt and debris accumulated on the foundation settling and cracks

Tower Base Maintenance and Inspections

Dayton 2013

Dirt and debris accumulation on your tower foundation can lead to catastrophic tower failure

Guy anchor failure is one of the most common causes of catastrophic tower failure determine if you have corrosive soil conditions in your area adequate guy anchor depth for local soil conditions use only heavy duty galvanized, forged hardware use tower manufacturer’s recommended guy anchor

design corrosive soil require professional guy anchor design elevated guy anchors require professional design

Guy AnchorDesign and Construction

Dayton 2013

Never use light duty home owner grade hardware

Inspect at least once every three years dig down at least six inches to inspect for anchor rod

corrosion missing hardware loose hardware corroded hardware

Guy Anchor Maintenance and Inspections

Dayton 2013

Anchor rod corrosion is a very serious threat to tower safety survival

Use heavy duty galvanized, forged hardware Use tower manufacturer’s recommended guy wire size

smaller guy wire risks catastrophic tower failure heavier guy wire reduces the tower’s load capacity

Tension guy wires to 10% of breaking strength less than 7% risks galloping guy wires and excessive tower

flexing in the wind greater than 15% risks guy wire vibration and reduced tower

load capacity guy wire vibration dampening hardware may be needed

Guy WireDesign and Construction

Dayton 2013

Never use light duty home owner grade hardware

Inspect three months after installation Inspect at least once every three years Inspect after all serious storms Check guy wire tension (7-15% of breaking strength) Check for:

damage from rubbing of chaffing of guy wire corrosion loose hardware

Guy Wire Maintenance and Inspections

Dayton 2013

Corroded guys and hardwarerisk catastrophic tower failure

Guy force must be properly distributed to the tower structure use the tower manufacturer’s recommended design

Heavy duty professional grade forged, galvanized hardware

Install turnbuckle safety wires Use articulated guy wire connections

10 degrees of free guy wire movement in any direction no chaffing or damage to guy wire or hardware from

frequent tensioning, loosening or movement of the guy wire in the wind

Guy Attachment (tower and anchor)Design and Construction

Dayton 2013

Use the manufacturer’s recommended guy attachments

Inspect guys at least once every three years Check all guy attachment hardware

missing or loose turnbuckle safety wires loose, missing or corroded hardware guy wire chaffing or rubbing Integrity of tower structure in the vicinity of each guy

attachment damaged tower structural components broken welds loose or missing hardware

Guy Attachment (tower and anchor) Maintenance and Inspections

Dayton 2013

Replace all degraded or missing guy attachment hardware

Use at least three ground rods adjacent to your tower foundation at least 8 feet from each other and the tower base

One ground rod for each guy anchor 8 foot galvanized ground rods (10 feet preferred) Large diameter (2/0) solid, tinned ground wire

rugged durable connections to tower and guys buried connections to ground rods (Cadweld preferred) buried wire between ground rods a tower base

Lightning Protection Design and Construction

Dayton 2013

Never use braided wire for tower grounding

Inspect all ground wire connections at least once every three years loose or missing hardware missing wires broken wires corrosion

Lightning Protection Maintenance and Inspections

Dayton 2013

Repair all damaged or missing ground wires and connections

Do not exceed the manufacturers load capacity

use adequate size control cable consider the total length of the control cable

rotator mounting hardware should be appropriate for your tower use galvanized steel or stainless steel hardware always use anti-galling compound on stainless steel hardware

RotatorDesign and Construction

Dayton 2013

An under rated rotator will fail prematurely

Inspect three months after installation

Inspect every three years

Check: excessive mechanical play in the wind corroded hardware

Rotator Maintenance and Inspections

Dayton 2013

An under rated rotator will be a major

maintenance problem

Appropriate antenna and mast for local wind and ice conditions heavy duty antenna when needed for local conditions

Use only galvanized or stainless steel hardware use anti-galling compound on stainless steel hardware

Use vibration dampening of antenna elements to avoid premature failure

Well designed coaxial cable connections to the antenna electrical and mechanical

Properly designed boom truss with professional quality hardware

Antenna and MastDesign and Construction

Dayton 2013

Select an appropriate antenna and mast for your local wind and ice conditions

Inspect at least once every three years loose or missing antenna hardware loose or missing boom truss hardware corroded hardware ultra violet radiation damaged hardware coaxial cable electrical connection to the antenna coaxial cable physical connection to the antenna damaged structural components

Antenna and Mast Maintenance and Inspections

Dayton 2013

Coaxial cable connections to your antenna are easily damaged by wind, rain and

UV

Select appropriate cables for local ultraviolet conditions Use appropriate hardware for tower attachment

consider local ultraviolet, wind and ice conditions #12 insulated solid copper wire is a good choice for

fastening cable to a tower high quality electrical tape (Scotch 88) is also a good

choice Electrically connect all coaxial cable shields to the tower

at the top and bottom of your tower

Coaxial Cables and Control CablesDesign and Construction

Dayton 2013

Fasten cables to your tower with high quality attachment hardware

Inspect at least once every three years loose, missing or UV damaged cable attachments UV damaged cables

Coaxial cables control cables and connectors damaged by water or moisture intrusion best inspected by using a time domain reflectometer,

vector network analyzer, VSWR meter or other appropriate techniques

good records are essential to detecting degraded coaxial cables

Coaxial Cables and Control Cables Maintenance and Inspections

Dayton 2013

Degraded coaxial cable seriously affects station competitiveness

Use this presentation to help you avoid the most common design and construction errors

Inspections are essential to long term tower and antenna reliability

Conduct major inspections during the first year after construction or major

modifications every three years after serious storms or damage

Summary

Dayton 2013

Regular inspections are essential to tower and antenna

safety and long term reliability