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Grounding

Grounding Practices

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4 Simple Rules for INU Grounding

• Each INU / IDU is required to be grounded separately to the rack ground bar.

• The INU / IDU ground wire needs to be a minimum of 4mm sq.

• The ground should be a green, PVC insulated, copper stranded wire.

• Grounds secured to indoor equipment and rack ground bar with correct size ring terminals

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Incorrect IDU Grounds

• The INU grounds shown here are daisy-chained and do not meet Stratex requirements

• Grounds need to be individually routed to the rack ground bar

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Correct IDU Grounds

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Correct Indoor Equipment Grounding

Rack Gnd Bar

IDU

IDU

IDU

IDU

Protect Switch

Simplified Block DiagramIndoor Equipment Grounding

• Each INU / IDU is individually grounded to the rack ground bar

• Ground wire 4mm sq. or greater• Grounds run neatly up the side

of the rack, tie-wrapped every 0.3m

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ODU Grounding

• Ground lead must be at least 16mm sq.• Follow reference manuals to determine ODU

attachment point• ODU ground lead connected to tower ground

bar or tower steel• Ground wire should not be looped or spiraled• Scrape paint or oxidation from tower to install

ODU ground using a clamp.

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Incorrect ODU Grounds

• The ODU grounds shown here are daisy-chained (green wire between ODU’s)

• Grounds need to be individually routed to the rack ground bar.

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Correct ODU Grounds

Each ODU is grounded separately – do not daisy-chain ODU grounds

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ODU Ground Lead

• Incorrect ODU ground• Ground lead should

always angle downward without being coiled

• This ground is looped before going back up to the ground clamp

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Correct ODU Ground Lead

• Ground lead runs downward toward tower ground point

Service loop

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Rack & Equipment Grounding

• Each chassis is grounded to the rack in which it is located. Most racks are either painted or power coated. Paint and power coating is an insulator and will insulate the various metal components of the rack and cabinets. A copper grounding bar should be located on the rack. All chassis within the rack to be connected to the copper bar with a minimum 4mm green wire. The station ground is also connected to the copper bar with a 16mm green cable.

* On sites that have more then one rack, each rack or cabinet should have its own copper grounding bar The copper ground bars must be connected together with a 16mm cable. Even if the racks and cabinets are bolted together.

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Rack Ground

• Rack ground must be at least 16mm, green PVC insulated, copper stranded wire

• Route rack ground from rack ground bar to station Master Ground Bar

• If cable entryway is high, ground the rack high• If entryway is low, ground the rack low• Place insulating mat or kit under rack if

mounted to a concrete floor

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High Entryway (1)

• Incorrect• Grounding at

the bottom of the rack will create a path for surge current, possibly damaging or destroying the equipment.

Rack Ground

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High Entryway (2)

• Correct• Grounding at

the top of the rack will minimize the risk of damaging current going through the rack.

Rack Ground

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Best Practices

Cable Grounding• At a minimum, the indoor to outdoor cable is required to be grounded at the top and bottom of the vertical cable run, as well as the cable entryway to the equipment room.

• All cable ground wires need to be angled downward as much as possible.

• Cable runs over 50m in vertical height require additional cable grounds.

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Ground Conductors

• Cable grounds at bottom of cable run

• Note that the ground wires go straight downward toward the tower ground bar

• Never exceed an 8 inch bend radius on ground conductors

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Coax Cable Grounding

• All transmission lines must be grounded to the tower at its uppermost point and lower most point if the tower is less than 150 feet (45.72m) tall.

• If the tower is taller than 150 feet (45.72m), then the grounding must be at the uppermost point and at intervals of no more than 75 feet (22.86m) until the bottom 150 feet (45.72m) section is reached.

• Coax and waveguide lines must use grounding kits designed for grounding the shield. All grounding kits must be properly weatherized to prevent bond deterioration.

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Cable Ground Locations for Lightning Protection

Time equates to distance, the further the shelter is from the tower, the more time the grounding system has to disperse the strike energy before reaching the equipment.

Ground at bottom of cable run should be placed about 1m above bend in cable

Ground at top of cable run, should be placed about 1 m below bend in cable

Ground at cable entryway should be connected to the ground bar usually located beneath the entryway

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Cable Ground Locations

Picture of transmission line grounds positioned about 1m above the bend where the coax goes from a vertical to a horizontal orientation.

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Grounding

• Integrated Ground* Building Steel* Air Conditioners* Power* Water Pipes* Cable Trays

• Isolated Ground* Equipment

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Ground Connections

• Only use correct ground lugs and terminals for the required wire sizes

• Use the correct tools for each size crimp. Use only die sizes called out by the manufacturer

• Perform correct # of crimps as needed for different wire sizes

• Use an antioxidant grease on all outdoor ground connections

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Common Ground Terminations

Blue Code

Single Lug

16mm Wire

2 or3 Crimp

Brown Code

Single Lug

# 2 Wire

3 Crimp

Blue Code

Ring Term

4mm Wire

1 Crimp

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Anti-corrosion Compounds

• Apply to all outdoor ground connections to prevent corrosive build up.

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Anti-corrosion Compounds

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Ground Measurements

•Specifications

•Locations

•Tools

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Ground Measurement Specifications

• Site/Tower Ground to Earth* 5 ohms max

• Site Ground Continuity* 1 ohm max

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Ground Measurements

• Ground conductor measurement using an AEMC clamp-on ground tester

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Ground Measurement Locations

• IDU/INU Ground• ODU Ground• Switch Ground• Rack Ground• Master Ground Bar• Cable Entryway Plate• All Cable Grounds• All Lightning Arrestor Grounds• Antenna Tower Legs

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Ground Testers

Tests tower/site ground to Planet Earth Clamp on tester

Tests continuity of site ground conductors and bonds.

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Lightning Protection

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Lightning – What is it?

Step LeaderDistance

10kV/m to 30kV/mE - Fields

The Larger the Charge, the Larger the Step

Typical Step 50m. @ 50µS per Step( 1µS jump, 49µS pause )

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Lightning Protection

The 45 degree “Cone of Protection”

• We used to believe that a tall structure provided a 45ºcone of protection, but side-mounted antennas were still hit by lightning.

• Any site with a tower over 50m tall should be evaluated using the “Rolling Ball” theory

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Rolling Ball Theory

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Why is it important?

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ESD Prevention

• Use ESD strap provided in installation kit when removing or installing INU / INUe modules

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Bend radius

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Lightning Protection Q & A

Lightning Protection

Q & A

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Cable Preparation

Cable Preparation

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Cable Preparations

• Use correct connector * 50 ohm

* Crimp / Crimp

• Weatherproofing

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50 ohm N-Type Connector for IF Cable

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Cable Terminations

Center Conductor

Dielectric

Wire Braid

Foil

Outer Insulation Jacket

Ensure that only the layers specified in the manufacture’s procedure are cut. Review the procedures before performing the cable preparation.

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Crimp Tools

Standard Crimping Tool

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Weatherproofing

• Wrapping Guidelines• 1. Ensure connectors are firmly hand-tightened, dry, and free from all

grease and dirt. If necessary clean with a rag lightly moistened with an alcohol-based cleaner.

• 2. Apply the tape tensioned, using at least a 75% overlay. The tensioning (slight stretching) of the tape is required to allow it to bind to the host and to amalgamate the layers.

• 3. Where possible, apply the tape 25 mm past the ends of the connector barrels to ensure the weatherproof bond extends beyond the areasrequiring protection. Regardless, the application of the tape must be such that there is no doubt as to the effectiveness of the sealing provided.

• 4. To avoid curl-back, do not stretch the tape too tightly at the end point and never stretch it until it tears. Always cut the tape instead.

• 5. To provide UV protection, an additional double wrap using vinyl tape must be applied using a 75% overlap.

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Cable Preparation Q & A

Cable Preparation

Q & A

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Antenna Considerations

• Drain Hole• Strut Requirement• Hardware Tightening Values

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Antenna Drain Holes

When the antenna is installed, and you are sure that the orientation is correct, be sure to remove the bottom drain hole.

Removing the top drain hole will allow water ingress into the antenna which will greatly reduce the receive signal level.

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Strut Requirement

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Antenna Hardware Torque Values

Stainless Steel M5 M6 M8 M10 M12 M16 M20

N-m 4.5 7.7 18.7 39.2 65.1 161

lb-ft 3.3 5.7 13.8 28.9 48 118.7

Galvanized Steel

N-m 2.7 4.5 11.1 22 38 95 185

lb-ft 2.0 3.3 8.1 16.2 28 70.1 136

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Antenna Considerations

Q & A

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Installation CIT

Installation Continuous Improvement Program

What is it?

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Continuous Improvement Program

• Provides Feedback From Installers• Difficult processes identified

* Recommended Improvements

• Easy processes identified• Suggestions on alternative install materials• Documentation Rating (scale of 1 – 10)• Overall Rating (scale of 1 – 10)

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Stratex Networks Global Helpdesks

Region Telephone # Fax # Contact/E-Mail

The AmericasSan Jose, CA

USA

1-800-362-9282Or

1-408-943-0777

1-408-944-1671Or

1-408-944-1801

sj_techsupport@stratexnet.com

Europe, Middle East, Africa

Hamilton, Scot

+44 1698 717 230 +44 1698 717 217 dmcglasupport@stratexnet.com

Asia PacificClark, Philippines

+63 45599 5192 +63 45 599 5196 dmcapsupport@stratexnet.com

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