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Cooper Bussmann BU-905U-L Wireless I/O Installation Manual
For example, an BU-SG900-6 antenna with a BU-CC20-SMA cable kit has a net gain of 2dB (i.e., +8 dB – 6 dB) at 900 MHz.
The BU-905U-L-R module has no limitation on antenna gain, as this module does not incorporate a radio transmitter.
The following table details the gains of some typical antennas:
Antenna Gain (dBi)
Dipole with integral 3m cable 0
Dipole without cable 2
5dBi Collinear (3dBd) 5
8dBi Collinear (6dBd) 8
3 element Yagi 5
6 element Yagi 10
The following table details losses for typical cables:
Cable Loss (dB per 10m) at 900 MHz
RG58 -5
RG213 -2.5
Cellfoil -3
Radio Transmission Distances
The unit will operate reliably over large distances depending on the:
• Antenna type;
• Antenna location;
• Amount of radio interference; and
• Radio path obstructions (e.g., hills or trees).
Typical reliable distances are:
Area Distance Additional information
USA/Canada 20+ miles 6dB net gain antenna configuration permitted (4W Equivalent RF power permitted).
Australia/NZ 20+ km Unity gain antenna configuration (1W Equivalent RF power permitted).
To achieve these distance, you must elevate at least one site on a hill or transmission tower.
Modules will operate reliably with some radio path obstruction; however obstructions also reduce the reliable distance.
Note: You must test all obstructed paths to check the reliability of the path.
You can achieve maximum transmission distances if the radio path has “line of sight.” For example, raising antennas above intermediate
obstructions including hills, trees, etc. Obstructions reduce the range; however they may not prevent a reliable path.
The closer the obstruction is to the antenna, the greater the blocking effect. For example, a group of trees around the antenna is a larger
obstruction than a group of trees further away from the antenna. You can achieve longer distances by mounting one antenna on top of a hill.
Note; Due to the earth’s curvature, you must elevate antennas higher than the ground level between the antennas for longer paths
(greater than 3 miles / 5 km).
The unit can tolerate larger amounts of obstructions for shorter distances. For very short distances, you can also mount the antennas inside
buildings.
If two BU-905U-L modules cannot communicate reliably, you can use a third 905U module as a “repeater” to receive and re-transmit messages.
This module may also have input/output (I/O) signals connected to it and form part of the I/O network.
3A1580Rev1.6