Kenwood TS-590SG Manual page 37

However, depending on the nature of the pulse noise, the noise blanker cannot suppress the noise effectively. In such a
case, by using other methods such as noise reduction in conjunction, the reception conditions may be improved.
Hints and Tips
● NB1 and NB2
Our noise blankers have been introduced since the era when vacuum tubes were used in transceivers. Back then, they were
known as "NB". With the development of the TS-930 at the beginning of the 1980s, noise blankers were divided into the
conventional NB1 and the new NB2. NB2 employs an NB circuit specially designed according to the cycle and pulse width of
pulse noise known as "Woodpecker", for which the conventional NB (NB1) has little effect on.
Subsequently, only an NB (NB1) was adopted with the disappearance of "Woodpecker". In the mid 2000s, however, a similar type
of pulse noise known as the "Dragon Noise" began to appear.
Starting from the release of the TS-590S in 2010, a pulse noise processing function using IF DSP was introduced as "NB2", which
is relatively effective for addressing the "Dragon Noise" pulse noise that NB1 is unable to handle. This is different from the "NB2"
function found on the TS-930 and subsequent models, which adopts an analog process. Their characteristics with respect to
pulse noise are also different.
● Differences in the operating principle of NB1 and NB2 for TS-590S/SG
Both the NB1 and NB2 functions operate at IF frequencies.
NB1 adopts the same analog circuit configuration, functions in the same way, and has the same effect as conventional models, It
removes areas where pulse noise exists together with the target signals (blanking). It is effective for pulse noise with a pulse width
that does not affect the auditory sensation of the target signals (100 μsec and below) but it does not perform blanking for longer
pulse widths. For this reason, it is not effective for pulse noise types such as the "Dragon Noise".
In contrast, the NB2 of the TS-590S/SG adopts a process based on IF DSP calculation. In the case of the NB1, signal blanking
is performed by differentiating the pulse noise based on the time constant of the NB circuit, while the NB2 differentiates the
pulse noise by comparing the target signal with the amplitude of the pulse noise, and attenuating the pulse noise component that
exceeds the amplitude of the target signal.
Figure 4-12 NB2: Inactive
Figure 4-13 NB2: Active
DSP 04
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