User manual

A-6 Appendix A: Path Evaluation Information
Moseley SL9003Q 602-12016 Revision G
A.2.2 Losses
Although the atmosphere and terrain over which a radio beam travels have a modifying effect
on the loss in a radio path, there is, for a given frequency and distance, a characteristic loss.
This loss increases with both distance and frequency. It is known as the free space loss and is
given by:
A = 96.6 + 20log10F + 20log10D
Where,
A = free space attenuation between isotropics in dB.
F = frequency in GHz.
D = path distance in miles.
A.2.3 Path Balance Sheet/System Calculations
A typical form for recording the gains and losses for a microwave path is shown in Section
A.2.7. Recall that the purpose of this tabulation is to determine the fade margin of the proposed
radio system. The magnitude of the fade margin is used in subsequent calculations of path
availability (up time).
The following instructions will aid you in completing the Path Calculation Balance Sheet (see
Section A.2.7):
Instructions
A. Line 1. Enter the power output of the transmitter in dBm. Examples: 5w = +37.0 dBm,
6.5w = +38.0 dBm, 7w = +38.5 dBm, 8w = +39.0 dBm (dBm = 30 + 10 Log Po [in watts]).
For the standard 9003Q, enter +30 dBm for 64 QAM and +33 dBm for 16 QAM
operation.
B. Lines 2 & 3. Enter Transmitter and Receiver antenna gains over an isotropic source.
Refer to the Antenna Gain table below for the power gain of the antenna. Note: If the
manufacturer quotes a gain in dBd (referred to a dipole), dBi is approximately dBd +1.1
dB.