User Manual

Determining the RF Link
22 Version 1.1 - 01/04/00
Calculating 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:
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 Working with
System Gain on page 18 for more information about system gain.
Note:
All path loss work must be completed by a professional installer.
Working with the Fade Margin
The amount that the system gain plus the total antenna gain exceeds the path loss is called
the Fade Margin. The Fade Margin is calculated as 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. The Fade Margin compensates for RF path fading due to
weather conditions or nearby objects that induce multi-path signaling.
The Fade Margin for the 300-24 is a minimum of 13dB. The sum of the cable losses,
connector losses, propagation losses, and the 13dB required Fade Margin should be less
than the system gain value of 93dB.
Note:
All fade margin work must be completed by a professional installer.
Formula: Path Loss = Tx and Rx Cable Loss + Tx and Rx Connector Loss +
Propagation Loss
Total antenna gain
is:
Tx Antenna Gain +
Rx Antenna Gain