Nr2 (Af Processing) - Kenwood TS-590SG Manual

04 DSP

4.6.6 NR2 (AF Processing)

NR2 is what is known as SPAC. It detects periodic signals contained in the RX signal and pieces together the detected
periodic signals to produce output receive audio. As a result, only the periodic signals in the receive audio emerge clearly.
NR1 based on an NR1 line enhancer is a filter in essence, but NR2 processes a RX signal in a different approach. Hence,
NR2 is very effective against a signal consisting of a single frequency such as a CW signal. And since this processing
method exhibits the characteristics of detecting the rising of a signal quickly, it has the effect to make the attack part of a
CW signal more distinguishable.
Hence, NR2 is a very beneficial function for CW operations. However, due to its operating principle, in the case of less
periodic signals such as voice, it may generate some noise where periodic signals are joined and, thereafter, the audio
quality may become less clear. In the actual operation, use NR1 in SSB mode, and select between NR1 and NR2 depending
on circumstances in CW mode.
For NR2, a user can set the autocorrelation time between 2 and 20 ms that aids greatly in detecting periodic signals. The
optimum autocorrelation time setting differs depending on the receive conditions, including the frequency of the target
signal contained in the RX signal and noise conditions. Try to find the best autocorrelation time setting while actually
receiving a signal.
Below, you can see the result of frequency analysis conducted on the receive audio containing a sine wave while NR2 is
inactive in Figure 4-19 and the result while NR2 is active in Figure 4-20.
Target signal
Figure 4-19 NR2: Inactive
Hints and Tips
● Variability of NR2 s Autocorrelation Time (Time Constant)
As with the operation for the variability of the NR1's effect level, NR2 allows for variation of the autocorrelation time (time constant).
In the case of the NR1, the role of this operation is, as the name suggests, to vary the noise reduction effect. The function of the
NR2, as described above, is to vary the cycle for picking out the target receiving signals. Unlike the NR1, the magnitude of the
effect is not variable, so you are recommended to set to the state that allows for listening with the greatest ease according to the
state of reception.
Also, distortion occurs when NR2 is used in the SSB mode. This is attributable to the operating principles of the NR2. It is an
extremely effective feature in the CW mode, so you can employ it as a exclusive function for CW. Nonetheless, NR2 may also be
effective for some types of noise during SSB reception, hence our decision to make it a selectable option.
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Target signal
Figure 4-20 NR2: Active