design, installation and maintenance of antennas, towers and rotators by frank donovan w3lpl for...
TRANSCRIPT
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