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1
The Leader in Industrial Data Communication Solutions
Training:RF Path – Will it work?
2
RF Design: Will this work?
ANTENNA
SRM6000
(425) 882-2206
12VDC
NC
4
DI
3
DO
2
CD
1
9 N
C
8 C
TS
7 R
TS
6 N
C
GD
5
DATA-LINC GROUP
P C I O
LightningArrestor
OmniAntenna
GroundWiring
LMR400Coax
LMR240Coax
SRMSeries
ANTENNA
SRM6000
(425) 882-2206
12VDC
NC
4
DI
3
DO
2
CD
1
9 N
C
8 C
TS
7 R
TS
6 N
C
GD
5
DATA-LINC GROUP
P C I O
LightningArrestor
OmniAntenna
GroundWiring
LMR400Coax
LMR240Coax
SRMSeries
RF Path12 miles
3
RF Design: SRM Radios
900MHz constants RF Path Loss with LOS:
First mile: -96dB Each doubling of range: -6dB
Transmitter Power: 1watt or 30dB Receiver Sensitivity: -108dB @ BER 1E-6
2.4GHz constants RF Path loss with LOS:
First mile: -106dB Each doubling of range: -6dB
Transmitter Power: 500milliwatts or 27dB Receiver Sensitivity: -108dB @ BER 1E-6
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RF Design: Throughput
Fact - Distance decreases throughput To maximize radio throughput and reliability:
Maximize RF quality (shorter coax, higher gain antennas) If practical, don’t use store-and-forward repeaters. Use
back-to-back repeaters? Use point-to-point architecture
To minimize system throughput requirements: Avoid cross-network data movement Only retrieve data once (Client/Server HMI model) Avoid HMIs as slaves Exchange data in large groups rather than several smaller
groups (minimize protocol overhead) Minimize data needed and increase update period
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RF Design: Antennas (1)
Use radio manufacturer approved antennas Common types:
Directional (yagi, parabolic) Omni-directional (di-pole)
Gain is specified in dBd or dBi and achieved by directing (focusing) RF emission
Emission patterns must be considered such that other sites are within focused area
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RF Design: Antennas (2)
Antenna coaxTo Lightning Arrestor
Mounting
Hose clamps
N Type male connector
Ground
Antenna coaxTo Lightning Arrestor RF Signal Direction
N Type male connector
Ground
7
RF Design: Coax (1)
Data-Linc offers two piece coax assembles: Good price/quality ratio Flexibility at radio mount position Lightning protection ready Bulkhead pass-through ready
Data-Linc only sells coax with end connectors that are inert gas welded, vapor sealed, and tested
Do not cut to length! Coil excess
8
RF Design: Coax (2)
Data-Linc uses Times Microwave Coax Website: www.timesmicrowave.com Losses:
COAX 900MHz 2.4GHzLMR240 7.6dB/100foot 12.9dB/100footLMR400 3.9dB/100foot 6.8dB/100foot
Failure Modes Improper end connections Moisture penetration Crimped, collapsed
Weather Seal
9
RF Design: Other RF Losses
SMA and N-Type Connectors Loss: .5dB each junction
Lightning Arrestors Always recommended for outdoor applications Install near equipment to be protected Loss: .1dB typical
N Type maleconnector N Type female
connectorN Type male
connector
SRM SeriesALL MODELS
10
RF Design: EIRP
Effective Isotropic Radiated Power (EIRP) Set by government regulation This is maximum measured RF emission from an
antenna In most countries not to exceed 4 watts Discussion: 1 watt can be increased to 4 watts by
doubling the power twice (1w x 2 x 2 = 4w). A doubling of power equals 3dB, thus, doubling twice is 6dB. This means a 6dB gain antenna can be directly connected to a 900MHz radio to emit the maximum legal EIRP.
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RF Design: Fade Margin
This is the amount of RF signal strength exceeding the minimum needed for a specified receive sensitivity.
Desired fade margin minimums: 20dB for SRM serial radios 30dB for SRM Ethernet radios
12
SRM Series900Mhz
SRM Series900Mhz
50 feetLMR400
50 feetLMR400
RF Path Theory Example 1
What is the fade margin – Will it work?
3dBOmni
3dBOmni
25 miles (40.2km)
30dBTransmit
-108 dBReceive
sensitivity
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