Up-Conversion; Rx Auxiliary Circuits - Kenwood TS-590SG Manual

01 RECEPTION

1.3 Up-Conversion

Difference of characteristics due to the pass bandwidth in the roofing filter can be viewed in graphs in Figure 1-5 and
Figure 1-6. So, let s see the characteristics of the up-conversion system in which the same front end configuration is used
as previous models. We will explain using the measurement result that compares the dynamic range characteristics of
TS-590S and of previous models in the 50 MHz band.
Measurement Conditions:
Receive
Frequency
Mode
Pass bandwidth
PRE AMP
Comparison target
(The measurement method is the same as that was applied to 14.2 MHz.)
In the 50 MHz band, the signal is received with up-conversion on both the TS-590S/SG and the TS-480HX/SAT. If the
separation between the target signal and the interfering signal drops below 20 kHz, the dynamic range decreases on both
transceivers. However, on the TS-590S/SG, the outcome is improved for 15 dB even within the pass bandwidth of the MCF.
This is thanks to the drastic modification of circuitry of the up-conversion section that was reviewed coupled with the down-
conversion path being added.
The same circuit is also used in WRC bands and in general coverage receiving as well as in the 50 MHz band, and therefore
the equivalent performance improvement is made in those bands.

1.4 RX Auxiliary Circuits

Typical built-in RX auxiliary circuits include the variable pass bandwidth circuit, notch filter and noise blanker (NB). In
modern HF transceivers, most of these auxiliary circuits (= auxiliary functions) are made possible by an arithmetic process
of the DSP. As well as the TS-590S/SG, only two auxiliary circuits operate genuinely at the IF stage: NB and AGC (ATT
circuit that functions by receiving the control signal provided by the DSP).
On the TS-590S/SG, there are two methods available to achieve noise blanking: NB1 and NB2. NB1 is realized by analog
processing and NB2 by digital processing of the IF DSP. Still retaining an analog noise blanker, TS-590S may seem out of
step with the times. But it is critical to have an analog noise blanker for a receiving system design using narrow roofing filters.
10
Figure 1-7 Dynamic Range in the 50 MHz Band
50.200 MHz
CW
500 Hz
OFF
TS-480HX/SAT (equipped with YF-107C CW filter)