Calculating System Operating Margin
SOM(dB) = Rx Input Signal Power (dBm) - Rx Sensitivity
(dBm)
SOM is a measure in dB of the signal loss your
system can with stand before it degrades to the error rate specified
at your Receiver Sensitivity threshold. A minimum 20 dB SOM is
recommended and many systems are designed with 30 dB+ due to additional
circumstances such as inadequate Fresnel clearance, desensitization,
intermod etc. This SOM calculator assumes an interference free,
free space environment. Note 5W=37 dBm, 1W=30 dBm
Free Space Loss =20Log10(Frequency in MHz) + 20Log10
(Distance in Miles) + 36.6
Rx Signal Level = Tx Power - Tx Cable Loss + Tx
Antenna Gain - FSL + Rx Antenna Gain - Rx Cable Loss
|