Kenwood TS-590SG Manual page 15

Noise is typically pulse-shaped and when the noise passes a narrow filter, the pulse waveform is changed to have a wider
(longer) pulse width.
Within the DSP, the processing block of the noise blanker is placed in a stage earlier than the filter block that determines
the final pass bandwidth. Thus, even if the final pass bandwidth is narrowed, the blanking operation can work properly,
free of the influence of the narrowed bandwidth.
However, roofing filters are located far earlier than the DSP, in the later stage of the first mixer. As a result, in the event the
bandwidth of the roofing filter becomes as narrow as 500 Hz, the pulse width becomes wider and a conventional digital
noise blanker would not deliver a sufficient blanking effect.
This is the exact case while down conversion is active on the TS-590S/SG and a digital noise blanker alone may not produce
a great enough effect. That is the reason we have placed a filter of pass bandwidth 6 kHz right after the first mixer. The
filter deters the transformation of the pulse shape and prevents false operation of the noise blanker due to adjacent signals
while sending the noise signals to the analog noise blanker.
During the up-conversion, the noise signal is derived from the second IF stage and delivered to the noise blanker circuit
as in previous models.
For the differences in operation for NB1 and NB2, refer to Hints and Tips in 04 DSP 4.6.2 Noise Blanker NB2 (IF
Processing) .
Hints and Tips
● Improvement of sensitivity in the BC band and alteration in ATT attenuation
On the TS-590S/SG, by changing the circuitry configuration inside the transceiver, you can change the sensitivity in the BC band
and the attenuation amount of the [ATT] key on the front panel.
Following is a figure that represents the TX-RX UNIT that has the circuitry configuration in question. By detaching the
lower case, you can access the jumper connectors CN101 through CN103.
1) Raising sensitivity in the BC band:
Remove the jumper for CN103 and insert the jumper into CN102. This will increase the sensitivity in the BC band for 20 dB.
(Assuming that there is the high output power in local broadcasting stations in the BC band, the factory default setting for
sensitivity is lowered by 20 dB.)
2) Changing the attenuation amount of ATT:
Remove the jumper of CN101. This changes the attenuation of ATT from 12 dB to 20 dB. (Store the removed jumper in a
secure place for future use.)
Figure 1-8 TX-RX UNIT
RECEPTION 01
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