AvMesh
®
RF Communications Systems
Installation & Service Manual
Latest products and information available at
www.avlite.com
19
3.7.3 Signal to Noise Ratio (SNR or S/N)
The signal to noise ratio is defined as the ratio of signal power at the receiver to the noise
floor and is often expressed in decibels. The lower the noise generated by the receiver or
the higher the signal strength, the higher/better the signal to noise ratio is. This translates
to a clearer signal transmission
In decibels, the Signal to noise ratio is given by the following formula:
Where V
S
is the strength of the desired signal and V
N
is the strength of the noisy signal,
both in units of voltage (i.e. Volts, millivolts, microvolts etc.) These measured values are
obtained from the Spectrum Analyzer as it shows the signals on a graphic display.
If the strength of the desired signal is equal to the strength of the noisy signal, the signal to
noise ratio will be zero. As a result, the desired signal will border on being unreadable since
the noise level severely competes with it.
Ideally, V
S
should be larger than V
N
so that the signal to noise ratio is positive. This will result
in the desired signal being readable. Therefore, as long as the desired signal is well above
the noise floor, then the transmission will be of a higher quality.
In situations where V
S
is smaller than V
N
, the signal to noise ratio is negative and reliable
communication is generally not possible unless the noise level is decreased and/or the
strength of the desired signal is increased.
