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Campbell Manufacturing R410, RF400, RF415 Overview, Link Analysis, How Far Can You Go, Distance Estimates for Spread Spectrum Radios, H-2

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Appendix H. Distance vs. Antenna Gain, Terrain, and Other Factors

How Far Can You Go?

Distance Estimates for Spread Spectrum Radios

Overview

There is a great deal of interest in estimating the distance you can expect to achieve with the RF400 radios. Also of interest are the effects of cable length, antenna gain, and terrain. Some of these items are easy to quantify (cable loss, for instance); others are difficult to quantify (such as the effect of ground reflections). They are all important, though, and affect how well the RF system performs.

Probably the best approach to take in making range estimates is to do a site survey that considers the topography, location of antennas and radios, and cable lengths, make some assumptions about the path losses, and see if there is still some net gain. If there is, or if it is close, the next course is to actually try it out.

Link Analysis

In an RF system, there are gains (transmitter power, antenna gains, and receiver sensitivity “gain”) and losses (cable loss and path loss). If the gains exceed the losses, you have a connection; any excess is the “link margin”.

Parenthetical values pertain to 2.4 GHZ

EXAMPLE GAINS			EXAMPLE LOSSES
Transmitter Power	20	(17)	Transmitter Cable	3
Transmitter Antenna	6		Free Space	120
Receiver Antenna	6		Receiver Cable	3
Receiver Sensitivity “gain”	110	(104)
TOTAL GAINS =	142	(133) dB	TOTAL LOSSES =	126 dB

Link Margin = (Total Gains) – (Total Losses) = 142 (133) – 126 = 16 (7) dB

A minimum of 6 dB of link margin is recommended.

Here is a block diagram of the various components of gain/loss:

Radio

Cable

Antenna

Free Space

Antenna

Cable

Radio

Transmitter

Loss

Gain

Loss

Gain

Loss

Receiver

Pt

-

Lt

+

Gt

-

Lp

+

Gr

-

Lr

=

Pr

Where:

Pt =>

transmitter output power, in dBm (20 dBm in the case of the RF400

or RF410)

Lt =>

cable loss between transmitter and antenna in dB (see Cable Loss section)

Gt =>

transmit antenna gain in dBi (dBi = dBd + 2.15)

Lp =>

path loss between isotropic antennas in dB (see Tables H-1, H-2)

Gr =>

receive antenna gain in dBi

Lr =>

cable loss between antenna and receiver in dB

H-2

Contents

RF400/RF410/RF415 Spread Spectrum Data Radio/Modem Warranty and Assistance – CAUTION – Page RF400 Series Table of Contents Introduction Quick Start Software Setup Troubleshooting D. Advanced Setup Standby Modes E. RF400 Series Port Pin Descriptions Short-Haul Modems H. Distance vs. Antenna Gain, Terrain, and Page Page RF400 Series Spread Spectrum Data Radio/Modems 1. Introduction 2. RF400 Series Specifications 3. Quick Start Step 1 – Set Up Base RF400 Step 2 – Set Up Remote RF400 Step 3 – LoggerNet/PC208W Set-up Step 4 – Connect 4. System Components 4.1 RF400 Series Data Radios 4.1.1 Indicator LEDs 4.1.2 Setup Menu 4.1.3 Networking 4.1.4Error Handling and Retries 4.1.4.2 Number of Retries 4.1.4.3 Number of Time Slots for Random Retry 4.1.4.4 Number of Bytes Transmitted before Delay 4.1.4.5 Sync Timer Setting 4.1.5 Received Signal Strength 4.2Power Supplies The RF400 series radio will sustain damage if the DC Pwr jack voltage ever exceeds Volts 4.3 Serial Cables 4.4 Antennas for the RF400 Series FCC OET Bulletin No. 63 (October 1993) approved antennas Page Page 4.5 Antenna Cables and Surge Protection 4.5.1 Antenna Cables 4.5.2 Electro-staticIssues 4.5.3Antenna Surge Protector Kit 5.Software Setup 5.1Point-to-point 5.2 Point-to-multipoint 5.3 Example Setups 5.3.1Direct PC to RF400 Series Base Station Setup Page 5.3.2Remote Station Setup Page 5.3.3 LoggerNet Configuration 5.3.4PC208W Configuration Page 6. Troubleshooting Page Page Appendix A. Part 15 FCC Compliance Warning Page Appendix B. Setup Menu B-2 B-3 B-4 Appendix C. RF400 Series Address and Address Mask Combined Network/ Radio Addresses C-2 C-3 C-4 Appendix D. Advanced Setup Standby Modes D-2 Appendix E. RF400 Series Port Pin Descriptions CS I/O FUNCTION E-2 Appendix F. Datalogger RS-232Port to RF400 Series Radio Page Appendix G. Short-HaulModems G-2 Appendix H. Distance vs. Antenna Gain, Terrain, and Other Factors Overview Link Analysis Transmitter Power Cable Loss Antenna Gain Receiver Sensitivity Path Loss Real World Distance Estimates Examples Range from ~9 to ~22 miles Range from ~14 to 30+ H-8 Appendix I. Phone to RF400 Series Page 2)AT Command Character: “-” Page Appendix J. Monitor CSAT3 via RF400 Series J-2 J-3 Page Appendix K. RF400/RF410 Pass/Fail Tests TESTING SC12 CABLE and PC COM PORT K-2 TESTING RF400/RF410s TESTING ANTENNAS K-5 TABLE K-1.900 MHz Gain Antenna Test Distances Antenna Power Ratio Distance Apart Over ¼ Wave Appendix L. RF400/RF410 Average Current Drain Calculations L-2 EXAMPLE #1 It ≈ 6.1 mA L-3 EXAMPLE #2 It ≈ 6.9 mA L-4 EXAMPLE #3 It ≈ 12.4 mA L-5 EXAMPLE #4 It ≈ 2.4 mA L-6 EXAMPLE #5 It ≈ 4.1 mA L-7 EXAMPLE #6 It ≈ 0.6 mA L-8 EXAMPLE #7 It ≈ 0.43 mA L-9 L-10 Page Campbell Scientific Companies Campbell Scientific, Inc. (CSI) Campbell Scientific Africa Pty. Ltd. (CSAf) Campbell Scientific Australia Pty. Ltd. (CSA) Campbell Scientific do Brazil Ltda. (CSB)