Cambium PTP 450 series, Руководство пользователя

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Analyzing the RF Environment PTP 450 User Guide
ptp-450 (July 2014)
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Calculating Fade Margin
Free space path loss is a major determinant in Rx (received) signal level. Rx signal level, in turn, is a major factor in
the system operating margin (fade margin), which is calculated as follows:

system operating margin (fade margin) dB =Rx signal level dB − Rx sensitivity dB
Thus, fade margin is the difference between strength of the received signal and the strength that the receiver
requires for maintaining a reliable link. A higher fade margin is characteristic of a more reliable link.
Analyzing the RF Environment
An essential element in RF network planning is the analysis of spectrum usage and the strength of the signals that
occupy the spectrum you are planning to use. Regardless of how you measure and log or chart the results you find
(through the Spectrum Analyzer in BHS feature or by using a spectrum analyzer), you should do so:

at various times of day.

on various days of the week.

periodically into the future.
As new RF neighbors move in or consumer devices in your spectrum proliferate, this will keep you aware of the
dynamic possibilities for interference with your network.
Mapping RF Neighbor Frequencies
These modules allow you to

use an BHS or an BHM that is temporarily transformed into an BHS, as a spectrum analyzer.

view a graphical display that shows power level in RSSI and dBm at 5-MHz increments throughout the
frequency band range, regardless of limited selections in the Custom Radio Frequency Scan Selection List
parameter of the BHS.

select an BHM channel that minimizes interference from other RF equipment.
The following procedure causes the BHS to drop any active RF link. If a link is dropped when the spectrum analysis begins,
the link can be re-established when either a 15-minute interval has elapsed or the spectrum analyzer feature is disabled.
Analyzing the spectrum
To use the built-in spectrum analyzer functionality of the BHS (or BHM that is temporarily configured as an BHS
for spectrum analysis via the BHM’s GUI) proceed as follows:
Procedure 3 Analyzing the spectrum
1
Predetermine a power source and interface that will work for the BHS in the area you want to analyze.
2
Take the BHS, power source, and interface device to the area.
3
Access the Tools web page of the BHS.
4
Click Start Timed Spectrum Analysis