Campbell RF401A Series, Instruction Manual

Page: 44 / 52

Appendix B. Distance vs. Antenna Gain, Terrain, and Other Factors
B-4
TABLE B-2. Cable Loss
Cable Type Outside Diameter Loss (dB/100 ft) @ 900 MHz
RG-58A/U 0.195 in 21.1
COAX RPSMA-L 0.195 in 11.1
RG-8 0.405 in 6.9
COAX NTN-L 0.405 in 4.5
LMR-400 0.405 in 3.9
*CSI stocked antenna cables are shaded.
Campbell Scientific’s COAX RPSMA-L uses LMR-195 antenna cable. Cable
loss is proportional to length as the following table illustrates.
TABLE B-3. LMR-195 Cable Loss vs. Length @ 900 MHz
Length (ft) Loss (dB)
100 11.1
50 5.6
25 2.8
10 1.1
6 0.7
B.2.5 Antenna Gain
Increasing antenna gains improves signal strength and, potentially, distance.
For example, in the context of free space path loss and all other factors being
equal, an increase of 6dB in antenna gain theoretically extends the attainable
distance by a factor of 2. An antenna’s gain is a function of directivity. For
highly directive antennas such as the Yagi, the narrower beam width makes
antenna alignment and orientation more critical.
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 RF401A series are:
TABLE B-4. Antenna Gain of Recommended Antennas
Mfg. Antenna Type Band Model
CSI Part
Number
dBd
Gain
dBi
Gain Size
Astron Omni (1/2 wave) 900 MHz AXH900 RP SMA R
#
14204 0 2.15 6.75 in
Antenex Collinear 900 MHz FG9023
#
14221 3 5.15 24 in
MaxRad Yagi 900 MHz BMOY8905
#
14201 9 11.15 21.4 in