Kenwood TS-890S In-Depth Manual page 45

● NR2 (SPAC Method)
The NR2 is for noise reduction with a speech processing system by using the Autocorrelation function, which is called
SPAC (Speech Processing system by use of the Auto Correlation function).
This system enables to detect periodic signals contained in the received signal and to piece together the periodic
signals detected as the received signal to be reproduced. Consequently, only the periodic signals in the received audio
are highlighted clearly.
While the line enhancer method of NR1 makes use of a filter, NR2 adopts a different approach to signal processing from
the line enhancer method. Therefore, NR2 is effective to signals with a single frequency such as CW signals. Also, the
SPAC method characteristically detects the rising of a signal quickly, so it also delivers an effect to make attack parts of
a CW signal more distinguishable.
These features make NR2 a very effective function in the CW mode. However, due to its operating principle, for less
periodic audio signals, noise may be generated at parts where periodic signals are pieced together, which may make
the audio less clear. In practical operation, we recommend the use of NR1 in the SSB mode and choose NR1 or NR2
depending on the circumstances in the CW mode.
The NR2 allows the autocorrelation time, which is important for periodic signal demodulation, to be specified within the
range of 2 to 20 ms.
The optimum autocorrelation time differs depending on the receive conditions such as the frequency of the target signal
and the noise contained in the received signal. Configure the correlation time while receiving signals to optimize the
effect.
The graphs below show how NR2 improves the S/N ratio of a tone signal.
Frequency (Hz)
Improvements of S/N ratio.
Frequency (Hz)
Fig. 49 Effect of NR2 S/N Ratio Improvement
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