HOW TO CHOOSE THE RIGHT ANTENNA
YAGI ANTENNA
A directional antenna. Focuses energy to one particular direction. In a point-to-point application, it is ideal to use Yagi antennas at both locations for extended range and better signal strength. Yagi antennas generate best results in point-to-multipoint applications when used with remote slave radios.
OMNI ANTENNA
Omni-directional antennas focus their energy equally in all directions. They typically have lesser range than a Yagi antenna of similar gain. Omni antennas are used in point-to-multipoint applications for the central master unit.
Point-to-Point
In this configuration, two radios will be talking to one another. Typical examples are serial-to-serial communication or peer-to-peer I/O wire replacement systems. Yagi antennas at both ends increase signal strength, range and reduce interference.Point-to-Multipoint
In a multipoint system, an Omni antenna is typically used as the master with individual Yagi antennas as “slaves” pointing to the “master” antenna for the best range and signal strength. A typical example is Modbus I/O configuration with a Radio Modem connected to an RTU master with several I/O nodes as slaves.
WIRELESS ANTENNA INSTALLATION TIPS
RF Range is influenced by several factors. Proper consideration during installation will help enhance the signal strength and range ensuring reliable operation.
TIP 1 - CLEAR RF PATH OF OBSTRUCTIONS
Make sure the RF path is clear of obstructions. Antennas should be installed where they can “see” each other as much as possible. Make sure the antennas are high enough above any obstructions in the RF path.
| SUGGESTED HEIGHT CLEAR OF OBSTRUCTIONS | |||
|---|---|---|---|
| Range | 2.4 GHz | 900 MHz | 868 MHz |
| 1000 ft (300 m) | 5.5 ft (1.7 m) | 8 ft (2.5 m) | 8.5 ft (2.6 m) |
| 1 mi (1.6 km) | 10.5 ft (3.2 m) | 16 ft (5 m) | 19.4 ft (5.9 m) |
| 5 mi (8 km) | — | 34 ft (10.5 m) | 46.6 ft (14.2 m) |
| 10 mi (16 km) | — | 47.5 ft (14.5 m) | 61 ft (18.6 m) |
TIP 2 - PAY ATTENTION TO ANTENNA ALIGNMENT
Make sure the antennas are aligned to center of the signal path and angle, and on the same level plane.
TIP 3 - KNOW YOUR OVERALL SYSTEM GAIN REQUIRED TO MEET THE DISTANCE
The more the distance between the radios, the more the overall system gain needs to be. A quick rule of thumb for the overall system gains vs. distance is as below:
| Radio Frequency & Wattage | 300 ft (100 m) | 1000 ft (300 m) | 1 mile (1.6 km) | 5 miles (8 km) | 10 miles (16 km) |
|---|---|---|---|---|---|
| 2.4 GHz, 60mW | 2.1 dB | >6 dB | >10 dB | — | — |
| 900 MHz, 1W | 2.1 dB | 2.1 dB | >3 dB | >6 dB | >10 dB |
| Note: RF signal is lost across cables and connections. Refer to Tip 4 to know the impact of cable lengths and connections and how to select the antenna gain to compensate for the signal loss. | |||||
TIP 4 - KNOW YOUR SIGNAL LOSSES AND THE REQUIRED ANTENNA GAIN
Signal is lost across cables and connectors. The longer the antenna cable and the more the number of connections, the more the signal loss. A larger antenna gain is necessary to compensate for these losses and to meet the required distance. As a rule of thumb, the RF range will be reduced by half for every 6 dB signal loss.
The lost signal has to be compensated by choosing a proper antenna gain. B&B’s 900 MHz Zlinx and Zlinx Xtreme radios come standard with a 3 dBi Omni antenna and the 2.4 GHz radios come with a 2.1 dBi gain Omni antenna. If more gain is necessary, choose a higher gain antenna depending on your system requirement.
The table below shows the signal loss across cables and connections.
| SIGNAL LOSS ACROSS COMPONENTS | ||
|---|---|---|
Signal Loss
| ||
868/900 MHz
|
2.4 GHz
| |
| Antenna Cable (LMR400) |
-3.9 dB/100 ft
|
-6.8 dB/100 ft
|
| Connectors (RP-SMA/N-Type) |
-0.5 dB
|
-0.5 dB
|
| Lightning Arrestors |
-1 dB
|
-1 dB
|
TIP 5 - USE THE MINIMUM CABLE LENGTH REQUIRED
Use the minimum cable length required. Do not run more cable than needed.
TIP 6 - DO NOT WRAP THE CABLES
Do not wrap or coil the cables around anything.
TIP 7 - USE DRIP LOOPS
Use drip loops at the cabinet. This keeps moisture from collecting between the connection joints and in the cabinet itself. When using cabinets, bottom cable entry is recommended versus side entry. Never run the cable in through the top of your cabinet.
TIP 8 - PROTECT THE ANTENNA CONNECTION
Protect the antenna connection with the correct vulcanizing rubberized tape.
TIP 9 - CORRECTLY PHASE THE YAGI WITH RESPECT TO THE OMNI BASE ANTENNA
Make sure Yagis are phased (oriented) correctly with respect to the Omni base antenna.
TIP 10 - CORRECTLY PHASE YAGIS WITH RESPECT TO EACH OTHER
Make sure Yagis are phased (oriented) correctly with respect to each other.
ADDITIONAL RESOURCES
| RANGE VARIABLES AND THEIR IMPACT | ||
|---|---|---|
| Range Variable | RF Range Reducer | RF Range Enhancer |
| Transmitter Power | Less | More |
| Receiver Sensitivity | More | Less |
| Antenna Gain | Less | More |
| Antenna Cable Length | More | Less |
| Number of Connectors | More | Less |
| Physical Obstructions | More | Less |
| Radio Frequency Interference | More | Less |
| Data Rate | More | Less |
The table below shows the maximum distance for different antenna and cable combinations at different terrains. Impact of weather is not factored in.
| HOW WILL ENVIRONMENTAL CONDITIONS AFFECT MY ANTENNA CHOICE? | ||
|---|---|---|
| 2.4 GHz Models | 868/900 MHz Models | |
| Indoor: No line of sight, limited number of frame-construction walls, multiple reflective surfaces | ||
| 500 ft (150 m) | Supplied antenna | Supplied antenna |
| 500-2600 ft (150-750 m) | — | Supplied antenna |
| Outdoor Unobstructed: Perfect RF conditions: Tower to Tower | ||
| Up to 1.4 mi (2.25 km) | Supplied antenna (no cable) | Supplied antenna (no cable) |
| 5 mi (8 km) | Omni (10 ft / 3 m cable) Yagi (20 ft / 6 m cable) | Supplied antenna (no cable) |
| 7 mi (11.2 km) | Yagi (50 ft / 15 m cable) | Supplied antenna (no cable) |
| 10 mi (16 km) | Yagi (20 ft / 6 m cable) | Supplied antenna (no cable) |
| 14 mi (22.5 km) | — | Omni (50 ft / 15 m cable) Yagi (50 ft / 15 m cable) |
| 40 mi (64 km) | — | Yagi (50 ft cable) |
| Outdoor Rural: Clear line of sight with elevated antennas and no obstructions | ||
| Up to 2900 ft (870 m) | Supplied antenna (no cable) | Supplied antenna (no cable) |
| 1 mi (1.6 km) | Omni (20 ft / 6 m cable) Yagi (50 ft / 15 m cable) | Supplied antenna (no cable) |
| 1.5 mi (2.4 km) | Omni (10 ft / 3 m cable) Yagi (50 ft / 15 m cable) | Supplied antenna (no cable) |
| 3 mi (4.8 km) | Yagi (20 ft / 6 m cable) | Supplied antenna (no cable) |
| 7 mi (11.2 km) | — | Omni (10 ft / 3 m cable) Yagi (50 ft / 15 m cable) |
| 10 mi (16 km) | — | Yagi (50 ft / 15 m cable) |
| 20 mi (32 km) | — | Yagi (10 ft / 3 m cable) |
| Outdoor Suburban: Line of sight but with some obstructions | ||
| Up to 1100 ft (330 m) | Supplied antenna (no cable) | Supplied antenna (no cable) |
| 2900 ft (870 m) | Omni (10 ft / 3 m cable) | Supplied antenna (no cable) |
| 1 mi (1.6 km) | Yagi (20 ft / 6 m cable) | Supplied antenna (no cable) |
| 1.5 mi (2.4 km) | — | Supplied antenna (no cable) |
| 2 mi (3.2 km) | — | Omni (20 ft / 6 m cable) Yagi (50 ft / 15 m cable) |
| 6 mi (9.6 km) | — | Yagi (10 ft / 6 m cable) |
| 7 mi (11.2 km) | — | Yagi (2 ft / 0.6 m cable) |
| Outdoor Urban: No clear line of sight, multiple reflective surfaces | ||
| Up to 500 ft (150 m) | Supplied antenna (no cable) | Supplied antenna (no cable) |
| 2700 ft (810 m) | Omni (10 ft / 3 m cable) Yagi (10 ft / 3 m cable) | Supplied antenna (no cable) |
| 3900 ft (1.2 km) | — | Supplied antenna (no cable) |
| 1 mi (1.6 km) | — | Omni (10 ft / 3 m cable) Yagi (10 ft / 3 m cable) |
| 2.5 mi (4 km) | — | Yagi (10 ft / 3 m cable) |
