# 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:

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)
```

## 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

Motorola R56 Standards and Guidelines for Communications Sites

## Tools

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