Codan Radio Radio Repeater Systems Training Guide - Manual (Page 53)

RADIO REPEATER SYSTEM | TRAINING GUIDE
Appendix D: Calculating Signal Levels Page 45
APPENDIX D: CALCULATING SIGNAL LEVELS
Antenna data, duplexer data, and coaxial cable and fi tting losses data can be found in Appendix F. With
this information and the path loss calculated in Appendix C, we can calculate our expected fade margin
and signal level over the path. On the following two pages are path calculation sheets for the BRIDGE
ARS to OFFICE and BRIDGE ARS to IRON MTN. ARS paths.
After noting the names used for each end of the path (BRIDGE ARS - OFFICE) starting with the lowest
powered, we enter the wattage of the transmitter (in this case, the repeater). Multiplying by 10 times
the logarithm of the wattage results in 6.0 dB being entered in the right hand column. The cable,
fi lter and connector losses are shown individually before adding together, only to make the licensing
process easier (when we get to it). The cable losses are calculated from the data in Appendix F, as is
the connector loss. Note that at the repeater end of the path, we’ll be using a duplexer; hence there are
four connectors used at -0.25 dB each (at 150 MHz), whereas at the other end of the path we will allow
for two connectors. The fi lter loss is taken from the manufacturer’s data sheet. The total loss shown is
-3.4 dB, leaving an antenna input power of +2.6 dBW. We decide to use an omni antenna rated at 6.0
dB gain, which when added to our antenna input power results in an Effective Radiated Power (ERP)
of 8.6 dBW.
The next section on the path calculation sheet is devoted to entering our propagation calculations (the
reason for our work on the profi le in Appendix C).