Selecting An If Filter; Criteria For Selecting The Rx-1 Or Rx-2 Path - Kenwood TS-590SG Service Manual
Hf / 50mhz transceiver
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TS-590SG
n From the preamplifi er (Q236) to the second IF
frequency (10.695MHz/11.374MHz)
The signal from the preamplifier (Q236) output to the
second IF amplifi er 1 (Q451) is spread into 2 paths: RX-1
and RX-2, depending on the frequency band (refer to table
4). The RX-1 path is selected when the "L" signal is added
to Q273, and the RX-2 path is selected if the "H" signal is
added.
The RX-1 path signal passes through the LPF for IF trap,
is integrated with LO1 (12.495 to 32.195MHz) in the quad-
balance fi rst mixer (Q263 to Q266), and is then converted
to the fi rst IF (11.374MHz). The fi rst IF signal is split further
into two paths when NB1 is selected and other than NB1 is
selected. If NB1 is not selected, the fi rst IF signal passes
through the 2-pole MCF (XF301) through path. Signals from
both paths then enters the second IF amplifi er 1 (Q451).
The RX-2 path signal passes through the LPF for IF trap,
is integrated with LO1 (73.120 to 133.095MHz) in the quad-
balance fi rst mixer (Q321 to Q324), and is then converted to
the fi rst IF (73.095MHz). The fi rst IF signal passes through
the 2-pole MCF (XF371), and by the trans-feedback type
NFB (negative feedback) fi rst IF amplifi er (Q391), is ampli-
fi ed by approximately 12dB. The amplifi ed signal is mixed
with LO2 (62.4MHz) in the second mixer (D422, D423),
converted to the second IF (10.695MHz), and then enters
the second IF amplifier 1 (Q451). The second mixer is a
passive type that uses a diode, and is a bilateral circuit that
converts both receive signal's frequency at the time of re-
ception and transmission signal's frequency at the time of
transmission.
Band
BPF selection classifi cation
135kHz/475kHz
BC
1.8MHz
3.5MHz
5MHz
7MHz
10MHz
14MHz
18MHz
21MHz
24MHz/28MHz
50MHz (TX)
50MHz (RX)
10
CIRCUIT DESCRIPTION
IF switching frequency criteria
f <522kHz
0.522≤ f <1.705MHz
1.705≤ f <2.50MHz
2.50≤ f <4.10MHz
4.10≤ f <6.90MHz
6.90≤ f <7.50MHz
7.50≤ f <10.5MHz
10.5≤ f <13.9MHz
13.9≤ f <14.5MHz
14.5≤ f <21.5MHz
21.5≤ f <30.0MHz
49.0≤ f <54.0MHz
30.0≤ f <60.0MHz
Table 4 Criteria for selecting the RX-1 or RX-2 path
The second IF signal that passed through the RX-1 or
RX-2 path is amplifi ed by approximately 13dB in the second
IF amplifi er 1 (Q451), and is then divided into 2 paths: the
NB (noise blanker) circuit and the blanking circuit (D461 to
D464). Blanking is carried out by D461 to D464.
Then, the second IF signal passes through the IF fi lter.
One of 5 filters is selected, depending on the frequency
and the mode (refer to table 5).
The second IF signal that passes through the IF fi lter en-
ters the AGC circuit which consists of the MOSFET (Q541).
The control voltage output from the DSP changes the at-
tenuation of the signal passing through. The signal is ampli-
fi ed by approximately 20dB at the second IF amplifi er (Q521,
Q522) and passed through the ATT diode (D525). The gain
difference between the RX-1 and RX-2 paths is then com-
pensated.
IF
IF fi lter
frequency
15kHz
10.695MHz
6kHz
2.7kHz
2.7kHz
11.374MHz
500Hz
Table 5 Selecting an IF fi lter
f <522kHz
0.522≤ f <1.705MHz
1.705≤ f <2.10MHz
2.10≤ f <3.40MHz
3.40≤ f <4.10MHz
4.10≤ f <6.90MHz
6.90≤ f <7.50MHz
7.50≤ f <10.5MHz
10.5≤ f <13.9MHz
13.9≤ f <14.5MHz
14.5≤ f <20.9MHz
20.9≤ f <21.5MHz
21.5≤ f <30.0MHz
49.0≤ f <54.0MHz
30.0≤ f <60.0MHz
Mode
FM
AM
SSB
FSK
4
4
4
4
4
4
4
4
4
4
IF frequency
TX IF
RX IF
73M
73M
11M
73M
11M
73M
73M
11M
73M
73M
11M
73M
11M
73M
-
-
73M
CW
4
4
4
RX-2
RX-2
RX-1
RX-2
RX-1
RX-2
RX-1
RX-2
RX-2
RX-1
RX-2
RX-1
RX-2
-
RX-2
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