Kathrein MSK 125 - Manual (Page 71)

71
TECHNICAL APPENDIX
SIGNAL-TO-NOISE RATIO
To determine the carrier-to-noise-ratio (C/N) for analogue
transponders, the following values must be known:
• Ambient noise level (adjust parabolic antenna so that no
satellite signal is received)
• max. reception signal
• Bandwidth correction
The following formula applies:
Example
Reception signal level with satellite signal
Ambient noise level without satellite signal
Carrier-to-noise (C/N) ratio
Bandwidth correction
for 26 MHz bandwidth
C/N of receiver
For exact C/N determination it is essential that the RF bandwidth
of the reception signal is considered.
Note
+75.5 dB
-55.0 dB
+20.5 dB
-6.4 dB
+14.1 dB
C/N = reception signal level - ambient noise level - bandwidth correction
(MSK 125 measurement bandwidth) 6 MHz
Bandwidth correction value = 10 log ––––––––––––––––––––––––––––––––––
RF bandwidth reception signal
Bandwidth correction value = 6.37 dB for 26 MHz bandwidth (Astra)
Bandwidth correction value = 7.78 dB for 36 MHz (Eutelsat, Intelsat,
Kopernikus)