RF Engineering

Before getting started, you will want to study or refresh your knowledge of Kirchhoff's Law, Ohm's Law and Watts Law

Electricity Supply

Direct Current (Battery)

UPS & Battery Backup

How to calculate what size battery system is needed for emergency backup
1. Find the current drain in Amps during transmit, receive and stand-by operation for each piece of equpment you will be attaching to the battery backup system. This usually can be found in owners manual specs page or on the internet.

2. Determine the equipment's Duty Cycle. Duty Cycle is expressed as a series of three percentages:

Transmit	Receive	Stand-By	Device
0	80	20	for a Scanner (low)
5	5	90	For a Transceiver (Medium)
100	0	0	For a Transmitter TV broadcast (High)

3. Use the following formula to calculate the average current required per device.

• Where i is the DC current in Amperes required during transmit (TX), receive (RX), and stand-by (SB)
• Where %Duty is the duty cycle represented as .xx ie. .50 is 50%

Average Current in Amps = (I_TX)(%Duty)+(I_RX)(%Duty)+(I_SB)(%Duty) 

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

Battery/UPS Size = (Average Current in Amps)x(Number of hours backup power required)

Grounding

Coax Grounding Grounding Bulkhead with supressors for your scanning station

• IEEE Std 142™ Recommended Practice for Grounding of Industrial and Commercial Power Systems.
• NFPA 780: Standard for the Installation of Lightning Protection Systems
• 2008 National Electrical Code online - Requires Site Registration
• List of PolyPhaser tech notes on Grounding PDF format

Reference Material

Books

• Newton's Telecom Dictionary, 25th Edition ISBN 0979387337
• The ARRL Handbook for Radio Communications ISBN 0872591441

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.

Related Wiki Pages

• FCC and FAA Tower Marking and Lighting Requirements
• Grounding Bulkhead with supressors for your scanning station

Related External Links

• Calculators for Electrical Engineers
• Maker site including RF and other electronics projects.
• Electrical Engineering Calculators
• Electronics Engineering Calculators
• Urgent Communications Mobile Radio Install Tips
• IEEE Vehicular Technology Society
• National training & certification program for the mobile electronics professional
• Repeater-Builder's Radio Site Standards
• Telecommunications Industry Association Online

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