Cable Loss - Wi-LAN Hopper Plus 120-24 Installation And Configuration Manual

Appendix A: Planning Your Wireless Link
For the 2.4 GHz band, the approximate is Fresnel Radius calculated as follows.
Formula:

Cable Loss

Cable and connector losses affect the operation of the wireless link and therefore should be kept to a
minimum by minimizing cable lengths and carefully selecting the type of cable. The two primary coaxial cable
specifications for the Hopper Plus 120-24 are:
• Cable must be 50 ohms nominal impedance
• Cable must be of a low loss type
The following is an example of cable loss ratings at 2.4 GHz.
Cable Type
Loss (dB/meter)
Note: When you calculate path loss, you will add 1dB at each end of the link to compensate for connector
losses in addition to the cable loss value.
Path Loss
Path loss describes the total RF attenuation throughout the system from Tx antenna to Rx antenna. This
includes the losses as the RF signal travels through space plus Tx and Rx cable loss, and Tx and Rx connector
loss. Use the following formula to calculate path loss.
Formula: Path Loss = Tx and Rx Cable Loss + Tx and Rx Connector Loss + Propagation Loss
Once you know the path loss, you can compare the value to the system gain value. If the system gain value is
greater than the path loss, the link is feasible. See
gain.
Fade Margin
Fade margin is the amount by which the system gain plus the total antenna gain exceeds the path loss.
Formula: Total antenna gain = Tx Antenna Gain + Rx Antenna Gain
As calculated, the fade margin is the number of dB that the received signal strength exceeds the minimum
receiver sensitivity. You require some level of fade margin for any wireless system to compensate for RF path
fading due to weather conditions or multipath interference.
The Wi-LAN recommended fade margin for the Hopper Plus 120-24 is a minimum of 15 dB. The sum of the
cable losses, connector losses, propagation losses, and the 15 dB required fade margin should be less than the
sum of the system gain and antenna gain.
112
Fresnel Radius (meters) =
LMR400 LMR600
0.22 0.144
System
( ⁄
3.4 d + d 8.12
km km
LDF2-50 LDF4-50A
0.190 0.128
Gain, page 110 for more information about system
Hopper Plus 120-24 Installation & Configuration Guide
2
)
LDF5-50A LDF6-50
0.073 0.053