RF Engineering

Electricity Supply

Alternating Current (Mains)

UPS & Battery Backup

How to calculate what size battery system is needed for emergency backup

1. Determine the average current drawn by all equipment to be provided with emergency backup power.
   • Find the DC current drain during transmit, receive and stand-by operation.
     • Determine the equipment's Duty Cycle.
       • Duty Cycle is expressed as a series of three percentages:
       • Transmit
       • Receive
       • Stand-By

Use the following formula to calculate the average DC current required.

IA.VE=(I_TX)(.5)+(I_RX)(.5)+(I_SB)(.90)

Where I is the DC current required during transmit (TX), receive (RX), and stand-b (SB) operation the above is for a 50%, 50%, 90% duty cycle.

If a different duty cycle is required change the percentages in the equation.

To determine the battery size required multiply the average current by the number of hours of backup power required.

Battery Size = (IA.VE)*(Hours of backup power required)

Grounding

Coax Grounding

Manuals

General Electric Lynchburg Book of Instructions (LBI) Term for GE Manuals
All LBI manuals are in Adobe PDF format and under 5Mb

• LBI-39148B Standards For Site Construction & Contract Install
• LBI-39179B Fiberglass & steel Comp & Lightweight Comm Shelter
• LBI-39184A Concrete Shelter Specifications - Bullet Resistant
• LBI-39185 Tower Requirements & General Spec - Installation

Motorola R56 Standards and Guidelines for Communications Sites

• Motorola Part Number 68-81089E50 Printed version
• Motorola Part Number 98-80384V83 CD-ROM version

Tools

1. Gives the current carrying ability for wires and wire bundles based on their AWG and Metric.

External Links

• Repeater-Builder's Radio Site Standards