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Campbell Manufacturing R410, RF400, RF415 Antenna Gain, Receiver Sensitivity, Path Loss, Mfg, dBd, dBi, H-4, Band, Size, Gain, Gain, less, Model, 915 MHz, Distance, Frequency, CSI Item #, Antenna Type

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

Antenna Gain

Antenna gain is specified either in dBi (decibels of gain relative to an isotropic radiator) or in dBd (decibels of gain relative to a dipole). The relationship is:

			dBi = dBd + 2.15
		Some antennas that are FCC approved for use with the RF400 series are:

Mfg.	Antenna Type	Band	Model	CSI Item #	dBd	dBi	Size
					Gain	Gain
Astron	Omni (1/2 wave)	900 MHz	AXH900 RP SMA R	14204	0	2.15	6.75”
Antenex	Collinear	900 MHz	FG9023	14221	3	5.15	24”
MaxRad	Yagi	900 MHz	BMOY8905	14201	9	11.15	21.4”
LINX	Omni (1/2 wave)	2.4 GHz	ANT-2.4-CW-RCT-RP	16005	0	2.15	4.5”
MaxRad	Enclosed Yagi	2.4 GHz	WISP24015PTNF	16755	13	15.1	17”

Receiver Sensitivity

Receiver sensitivity is usually specified in dBm for a specific bit error rate (BER). The transceiver module used in the RF400 (either 900 MHz radio) is specified at –110 dBm at ~10-4raw BER.

If the received signal strength is greater than the receiver sensitivity, a link can be established. Any excess signal strength above the receiver sensitivity is “link margin”, and is a very good thing; a minimum of 6 dB of link margin should be sought.

Path Loss

We have combined in this section the normal “free space” path loss (only seen in mountaintop to mountaintop scenarios) with loss due to ground reflections, diffraction, leaf/forest absorption, etc. It is all loss!

A starting point is the “free space” path loss. Here are two equations for this:

		Lp (dB) = 32.4 + 20 x log( f ) + 20 x log ( d )						dB	(f in MHz, d in km)
		Lp (dB) = 36.6 + 20 x log( f ) + 20 x log ( d )						dB	(f in MHz, d in miles)
		Here is a table showing the free space path loss (in dB). Note the effect of
		frequency.

Frequency						Distance
	1 mi.		2 mi.	4 mi.	8 mi.	10 mi.	16 mi.	22 mi.		26 mi.	30 mi.
400 MHz	89		95	101	107	109	113	115		117	118
915 MHz	96		102	108	114	116	120	123		124	125
2.4 GHz	104		110	116	122	124	128	131		133	134

Notice the relationship between path loss and distance: each time you double the distance, you lose 6 dB of signal under free space conditions. Or, put another way, if you add 6 dB of gain (for example with 6 dB of additional antenna gain, or 6 dB less cable loss), you can double the distance for free space conditions.

H-4

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)